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I got one of those dongles from my insurance company that plugged into the ODB2 port and reported my driving habits.

I was a bad driver. It would frequently beep at me to let me know that I had braked too hard. I was mystified. "What should I have done differently," I'd think, as I raged at the objective machine that judged me so.

The next time my brother came to visit, he called mom. "Oh, and presidentender is a good driver now." I didn't put the pieces together right away, but it turned out that the dongle had actually trained me, like a dog's shock collar.

The reason for my too-frequent hard-braking events wasn't speed, although that would be a contributing factor. It was a lack of appropriate following distance. Because I'd follow the drivers in front of me too closely I'd have to brake hard if they did... Or if they drive normally and happened to have a turn coming up.

Over the period I had the insurance spy box in my truck I learned without thinking about it to increase my following distance, which meant that riding with me as a passenger was more comfortable and it beeped less often. Of course since I'd been so naughty early during the evaluation they didn't decrease my rates, but I think the training probably did make me statistically less likely to crash.

Maintaining a safe following distance is incredibly challenging on busy freeways where hard braking is often 'required'. Most people have likely found themselves in this situation: vehicle changes lanes in front of you; you slow down to maintain a safe following distance, another car sees a gap and changes lanes in front of you. Repeat for your entire commute.

Incredibly frustrating, and I've driven all over North America - there's practically no major city where this doesn't happen. If you're not maintaining a safe following distance on city/residential streets, that's a different matter.

> vehicle changes lanes in front of you;

I will never understand why this is so rage-inducing for people.

Changing lanes is a necessary part of navigating, even during busy traffic. People on an on-ramp will need to get in front of somebody. People needing to move back to the right because their exist is coming up will need to get in front of somebody.

Your lane is not a birth right. Let people merge.

> you slow down to maintain a safe following distance, another car sees a gap and changes lanes in front of you. Repeat for your entire commute.

This happens because literally everyone is tailgating each other so hard that the gap in front of you is the only gap that exists for people to change lanes to either get on or off the highway.

It's frustrating because someone is taking your safety buffer as their opportunity to travel faster. And it results in you having to travel slower and slower to maintain the gap that is constantly consumed, tragedy of the commons style, by opportunists.

Slow down a bit to create another buffer. You can even do this before they have merged, as part of the bit where you allow them to safely merge.

I think if you reflect a bit you'll find you are being the same kind of person as them, if you are getting angry that you have to slow down and give up space for someone else. I understand some people can be aggressive though, that can be frustrating regardless of the outcome.

I don't think you're understanding. The point is that 20 people in a row will take advantage of your buffer to slow you down again and again and again, which makes you get to your destination later... because they're being selfish to get somewhere faster, and you're not so you get to where you're going slower.

We're not talking about where they're changing lanes to take the next exit. We're talking about where your lane happens to be moving faster, so they merge in front of you in an unsafe way to take advantage of that and just stay there. Why should you be expected to give them space, as you suggest? How is that fair, that they should get to their destination faster instead of you? Do you not see how that's going to rightfully make someone angry? When they should be waiting for a safe space to open up, rather than forcing you to slow down to create one?

I understand perfectly, 20 years driving, I think people just don't like that the safe answer is to be slow. You will not fix others behaviour, so your options are be slow and generous, get out of the chaotic lanes (unless that's all of them), or join them and be aggressive, claim space, be stressed and annoyed your whole trip.

There is no solution to traffic here sorry, this is more about managing your own frustration and expectations when faced with people at their worst, in the worst form of transport.

The total, confirmed, 100% effective solution is to never commute by highway during peak hours, but few get that option.

I object to the "late" argument made by etho's parent. The difference in time to destination will inevitably be dominated by lights, in city travel, not by modest speed differences (say 45 vs 55) on a highway. Being safe & out of the way is the trick! It would be nice if we got rid of left & u turns and build our roads for that!

45 vs. 55 is not modest; that's 5 minutes over only 20 miles. Up around 60 vs. 70 is where it becomes "modest" IMO.

So, 3 stoplights worth of time?

Or 0.1 of billable hours, which for many people here is at least enough to pay for lunch.

There is no solution to traffic here

There is, people just don’t want to hear it, and it isn’t a quick fix…

Build more of our towns and cities such that driving everywhere isn’t necessary.

Thanks for writing this, it reminded of how unfun driving really is. I realised how blessed I am now with not having to drive anywhere anymore.

I am going to validate what you say here.

Ehto is correct and this is the way. I'll go further and say that if someone is tailgating you and it's pissing you off, generously let them pass. Literally pull to the side of the road if you must.

The issue is that when you slow down, you’re (a) creating ‘turbulence’ in the traffic flow with increased speed differential between cars and increased lane changes, which increases accident risk for everybody, and (b) it’s not even solving the problem because you still perpetually have some impatient driver wedging themself in directly in front of you, deleting your buffer zone.

It’s safer to drive a little closer, keep up with other traffic and defend what gap you can in front of you.

Agree with your conclusion here, though. The best response is to simply not drive in this kind of traffic.

Hard disagree. It is not safer to ignore your safety buffer. It is certainly not safer to defend your buffer.

If traffic is very busy, the trick is to just accept people will wedge in front of you and keep going slightly smaller each time to increase the buffer again. You might create 'turbulence', which might possibly decrease the safety a bit for all the impatient drivers doing the wedging. But it increases your own safety. And therefore also that of the people following you and your passengers.

I'm also not convinced on the 'turbulence' part. Keeping a buffer smoothes out any sudden speed variations of the people in front of you, which makes the traffic behind you flow better.

And it might maybe feel a lot slower to let a 100 cars go in front of you on your commute, but just driving 99km/h when the person in front of you does 100 is enough to increase your gap and it makes a whopping 1% of difference.

The only thing is: sometimes a road is just too busy and the space for a buffer just isn't there to begin with. At that point the speeds should go down to accommodate the smaller buffers, which is actually what happens here in the netherlands as long as there aren't too many people ignoring the speeds advisory boards above the highway.

> The issue is that when you slow down, you’re (a) creating ‘turbulence’ in the traffic flow with increased speed differential between cars and increased lane changes, which increases accident risk for everybody, and (b) it’s not even solving the problem because you still perpetually have some impatient driver wedging themself in directly in front of you, deleting your buffer zone.

That's very obviously not true. Slowing down always reduces energy in the system and always reduces global turbulence. It's one of the reasons that countries that lower speed limits see journey times reduce.

Is there a statistics name for the last part? I'd like to compare different countries. It's definitely NOT true in Colombia at least, which makes me believe OP more.

We in Colombia had a public service announcement where it showed someone driving really fast (while still respecting semaphores), and another one going with just enough speed. In the end, they both reach the last semaphore almost at the same time and then they part ways. Essentially it shows that driving crazy fast in the city doesn't necessarily gets you faster to your destination.

Now that I'm an adult, I tested it several times, and it matches 90% of my attempts, but that's in the city, with semaphores. No way I'd think letting everybody steal everybody else's buffer would provide for a reduction in journey time, even in highways. You're adding items to a queue, it'll take longer.

Now, it is probably safer, but we can only take so much even if we are not in a rush.

Slowing down on a busy highway does not reduce turbulence at all, it add chaos and unpredictability to the system. Once car suddenly slowing down to create a buffer zone causes the car behind to slow more and more and can often lead to a stop further back. This has been proven time and again on closed loop systems studying highway traffic flow. They are known as "phantom" traffic jams or shockwave traffic jams. Example, https://www.newscientist.com/article/dn13402-shockwave-traff...

> Slowing down on a busy highway does not reduce turbulence at all, it add chaos and unpredictability to the system. Once car suddenly slowing down...

I agree that slowing down "suddenly" causes turbulence. However, slowing down *gradually* allows you to build up a safety buffer which in turn allows you to avoid slowing down suddenly.

Yes, and they are caused by sudden decelerations which are the result of many factors, including driving too fast for the conditions, roadway, and traffic, and tailgating.

> Slowing down on a busy highway does not reduce turbulence at all,

The only thing that reduces global turbulence reliably on any roadway is reducing speed. All the simulations and real-world implementations show this. It's unambiguous and uncontroversial, except that it requires drivers to slow down, which is politically untenable in many jurisdictions.

It is more dangerous to be slow and have people constantly merging in front of you, rather than be slightly faster and not have all the merging. Accidents happen when vehicles are going different speeds, all things equal.

That seems like a surprising enough statement to be backed up by data. What is your source?

Everything I've read points toward larger margins of safety (longer distances, slower speeds) being safer.

See e.g. https://publications.lib.chalmers.se/records/fulltext/252480...

American road laws are insane here. The law should be simple; you must be in the outside lane at all times unless you are overtaking, and once you're done overtaking, you should merge back into the outside lane.

https://www.highwaycodeuk.co.uk/overtaking.html

As far as I know that’s the law in every state I’ve driven in, but enforcement is pretty much nonexistent. Some states like Texas or Louisiana might have signs reminding people to stay out of the inner lanes except for passing but I’ve never heard of anyone getting a ticket over it. What’s enforcement like in the UK?

For example, the specific law in California: https://leginfo.legislature.ca.gov/faces/codes_displaySectio...

Vigorous.

Confusingly, the slow lane is called the "inside lane" in the UK, even though it's on the edge of the road and the fast lanes are in the middle.

That used to be the case in Ireland too, but confusion due to cultural contamination means pretty much everyone moved to numbering lanes (from the "outside"/"slow"/leftmost lane).

I've been driving in Ireland for 30 years and I've never heard anyone number lanes. For me it's left/slow; middle; or right/fast lane.

When I did my B license test probably about 30 years ago, the Rules of the Road all referenced inside/outside lanes. When I did my CE license last year, it had been updated to only use lanes 1, 2, 3 etc.

Obviously fast and slow are just colloquial terms.

I wish.

Seems like this is the only place where the verge is in the inside.

That's fine when traffic is light. At rush hour, all lanes are full and nobody is overtaking.

That seems rather inefficient on an 8– or 16–lane road.

You might be a bad driver and not even know it.

This is dangerous nonsense. It's basically just a justification people find in order to feel good about their unsafe driving.

You’re the problem because of the way you are thinking. You don’t own the asphalt in front of you. You’re angry because in your mind you do, and you feel righteous about it. That’s why you are casting a moral judgement about them.

The most efficient throughput of the road system is not for people to “politely” queue up for 5 miles. People should be utilizing the rod and merging in an orderly manner. By adopting some arbitrary self imposed practice that is leading to 20 drivers cutting in front of you, are the one creating an unsafe situation.

> You don’t own the asphalt in front of you.

Correct, but you _need_ the asphalt in front of you for both safe driving and also to avoid cascading hard braking events. I also don't own the asphalt under me or behind me too, so it's kinda a silly statement tbh.

This youtube talks about it: https://www.youtube.com/watch?v=iHzzSao6ypE

You do, but if you leave so much that 20 cars are pulling in front of you, you’ve either driving too slow or misjudged and left unnecessary space. At 15-20 mph traffic speeds, you need 8-20 feet. Ideally, cars in a multiple lane to one lane exit scenario should be zipper merging when congestion reduces speeds. Engineers model this behavior and try to design roads to encourage it.

If you do that and get angry when people change lanes in front of you, you have consciously or subconsciously decided you own that 20 foot gap. That reaction impairs judgement and causes accidents.

If you actually want the safest option then you should merge all the way right and keep slowing down. Noone is going to merge right if they are trying to go faster, they will only do it to get off the offramp. Meaning the gap will reopen as people exit through the offramp or merge left into faster lanes.

If you choose to go in the fastlane in traffic you should understand that it will have people who do not care about the following distance as much and are just trying to go as fast as possible.

I have found that often times in heavy traffic the rightmost lane can be just as fast or actually faster than a middle or left lane.

> Noone is going to merge right if they are trying to go faster

In my experience even cars that are not trying to go faster will happily merge in front of you unsafely all the time, just because they don't understand the concept of a safe distance.

> If you choose to go in the fastlane in traffic you should understand that it will have people who do not care about the following distance as much and are just trying to go as fast as possible.

It's not about choosing to go in the fast lane. It's about the fact that in heavy traffic, you have no idea which lane will be fastest, because they're all heavy and which one is fastest keeps switching.

> I have found that often times in heavy traffic the rightmost lane can be just as fast or actually faster than a middle or left lane.

That's exactly my point. Which is why you can be in the right lane, and tons of people from the slower lane will try to merge in front of you if you're keeping a safe distance from the car in front.

Your advice is staying in the right lane doesn't apply in these situations.

This is a long thread of people talking past each other. The bottom line is simply this: if you want to drive with a larger-than-average following distance (call it whatever you want, a safety buffer, a "proper" following distance, the point is it is a distance less than the average following distance of the other drivers on the road) then you have to accept that you will not be able to drive at the same speed as the other traffic on the road. It's physically impossible. It can be psychologically frustrating because you see all the cars around you moving at X mph but your self-imposed constraints mean you can only make way at (X minus Y) mph. But them's the breaks, no pun intended

> It can be psychologically frustrating because you see all the cars around you moving at X mph but your self-imposed constraints mean you can only make way at (X minus Y) mph.

This is correct, but I get the sense that people overestimate Y.

Let's say you're driving 60 mph and following the "three second rule" which gives you a ~264 foot safety buffer. A driver then cuts into this safety buffer. Let's assume they like to go fast and enter closer to the front of the buffer so they reduce your safety buffer down to two seconds. In response, you gradually rebuild the safety buffer back to three seconds, costing you an extra second. Soon after you rebuild the safety buffer another car cuts in front of you. Let's say this process repeats every mile of your journey, costing you an extra second every time. This results in you traveling slightly over ~59 mph, making Y = ~1 mph.

Compare that to the lifetime odds of dying in a car crash in the U.S. which is roughly 1 in 100. It's hard to eliminate that entirely, but I'm willing to spend an extra ~1s per car that cuts in front of me to reduce it for myself and my passengers.

Not so. Keeping a constant distance from the car ahead means both cars are moving at the same speed. When a jerk cuts in, after a moment all 3 cars will be moving at the same speed.

We are saying the same thing. When a jerk cuts in, drivers readjust their speed to maintain desired following distance. Net effect, slower speed for all but the lead car

If you personally start with that slower speed to begin with (AKA much longer following distance), you don't have to worry about adjusting down

>It can be psychologically frustrating

True, though-

I like being a traffic hacker--come on in, plenty of room!

Weaving into the little spaces is my version of traffic hacking. I estimate every time I can do that, I shave 1-2 seconds off of my commute.

i'm upvoting you assuming you were being sarcastic. if not, i hope you die in a fire of your own making. (also sarcastic)

Thanks. (sarcastic)

Everyone merges into your lane

Their old lane speeds up because many cars departed it

Everyone merges back to their old lane

You're back where you started.

You mean 20 people who were trying to merge finally get to merge because someone came past who wasn't a massive asshole?

To be completely clear the conversation is entirely not about zipper merging, but about people who are using safety gaps as opportunities for them to traffic weave attaining a faster than average travel speed at the cost of every one else's average travel speed and safety

That person then gets screwed.

Screwed person: WTF?

People doing the screwing: ‘oh thank god’

The really irritating part - society saying ‘oh, that’s not happening you should continue to be screwed’

Nobody is getting screwed. I've been the person making the gap many many times. You just ignore them, it isn't hard - they are way up there and I'm way back here, plenty of space. I just keep on with my business of safely driving. Sure I often wish I could go the speed limit - but in reality I'm going almost as fast as they are so it isn't like a few feet lost costs me anything. Odds are I'll be stopped at a red light and lose a lot more time once I get off the highway.

Besides, there are only a few people who ever merge in front of me (and then those who don't merge block their lane so nobody else can get in).

In high traffic you’re definitely being screwed - both by the continuing lack of a proper safety gap, and by not being able to go a normal speed. Which does add up in many of these situations.

But I guess we should just all self gaslight to feel better about it?

In heavy traffic nobody is going "normal speed". I'm not going significantly slower than anyone else.

In Bay Area traffic I’d literally be not moving at all for most of the time if I followed you advice, in heavy traffic. That’s the exact situation I’m talking about.

60 (20*3) car lengths at 20 mph is 30 seconds

20 people in a row is like 200 meters. Absolutely negligible to your travel time.

> 20 people in a row will take advantage of your buffer to slow you down again and again and again, which makes you get to your destination later...

30 seconds later, so what?

you missed the fact that most people either aren't signaling or do it right as they're already cutting in.

that's hardly safe when it's already tight with a safety buffer as it is.

provided they use a signal as required by law and taught in the drivers handbook, they'd likely be let into the new lane without any judgement.

-Slow down a bit to create another buffer.

Now you've just created a shockwave traffic jam.

No, the person who wedged themselves into an unsafe/too-short opening created the shockwave traffic jam. But, yeah, that's the end result.

No. That happens when people drive too close to each other and brake. Not when you let off the gas slightly to maintain a gap which prevents this exact thing.

The entire reason this happens is because 98% of people are morons who drive up the next guy's ass. If everyone kept a proper distance it wouldn't happen at all.

Or... you just drive so slow the gap is constantly growing. You can focus on fuel economy instead.

Not to mention if that if somebody needs to come over, the proper thing to do is signal first. Then I'm happy to politely ease off a bit and open more space for them to come over safely.

It's the people who aggressively slide right over just a few feet in front of me (cutting off nearly all of my safety buffer) without so much as a signal that really drive me nuts.

In the UK we are taught that you should not signal until you are ready to manoeuvre. If you follow the rules exactly this can put you in the unfortunate position of being penned in behind shower traffic.

It's the people who hit the gas when they see your signal, that really irk me. In Austin I stopped signaling because it was a punished behavior.

My experience driving in MA and NY was similar, but so often it was because a rusted out shitbox was trying to merge in that would slow down traffic significantly, and not only put me at risk of rear ending them, but being rear ended myself.

When flows merge, there's turbulence. There's less turbulence if the flows are more closely matched, including speed.

Unless I'm the last car in a line and there's plenty of open space behind me. Then you should just wait until after I've passed before merging, because otherwise you create a little ripple in the flow. A few ripples and you got a wave, and that's how you get traffic.

So for the love of gods, if you're merging, even if you signal, match speeds for merging. If you're too slow to match speed, then suck it up buttercup, and hang out in the right lane until there's an opening.

It seems like a tragedy, but actually it can be a boon as long as you travel in neither the leftmost nor rightmost lane. The majority of the traffic entering your buffer will be exiting your buffer out the other side as soon as they can, so you can just chug along at a (greatly reduced, but) consistent speed. Meanwhile, the traffic to either side of you is in standstill, paralyzed by your bow wake.

It's wild to me how often the left lane is not the fastest lane.

I've had times where the right lane ends up being the fastest. On I-5 near Woodburn, OR, it's 3 lanes. So many drivers, including truckers, will often stay out of the right lane entirely to avoid being caught up in traffic coming on/off. Meanwhile, the left lane is going 5 mph under the limit because there's a left-lane camper somewhere miles ahead. So I can fly past everybody in the right lane because there's actually barely any traffic coming on/off and everybody is avoiding the right lane for no reason at all.

> On I-5 near Woodburn, OR

The section of I-5 between Portland and Salem is absolutely psychotic, and I have never been able to reason out exactly why. It consistently has a left lane jammed with angry people going at or below the speed limit, a fairly normal center lane filled with cruisers, and a mostly empty right lane with the occasional big rig and regular very-high-speed cars expressing their frustration with the left lane by going 25+ mph over the limit in the right lane.

I know that's what you basically just said. Just venting. The driver behavior in that section of freeway confounds me, and I do not know what the underlying cause is. It is otherwise an unremarkable bit of interstate like any other.

It's wild to me that it's allowed and accepted to overtake on the right on US highways.

The alternative is that you're stuck going 10+ mph under the limit because of a left lane hog.

Banning passing on the right only works if keep-right-except-to-pass laws exist and are thoroughly enforced. Most states in the USA don't have keep-right laws, and those that do, it's never enforced, so many people don't even know it's actually the law.

EDIT: US-26 westbound immediately outside downtown Portland is notorious for left lane campers. The limit is 50 mph, but without fail, there's some moron going 40 mph in the left lane. You wanna go slow? Fine, but do it in the right lane where you belong.

AFAIK all US states have some form of "keep right" or "slow poke" laws in various forms that distill down to keep right, except to pass.

So the laws do exist, they just are never enforced. Even when said left lane campers cruise by state patrol, I never see them stopped. Hell, I rarely see them stop people going 15+ over the limit either so not actually sure what they're doing.

It's generally not allowed, but that doesn't stop people just like the speed limit doesn't stop them.

> It's generally not allowed

Common misconception, actually.

There is not a single state in the USA where using the right lane to pass slower traffic in the left/center lanes is illegal. It is allowed everywhere.

That's the freedom we're talking about when we say "land of the free".

It's not the fastest often because it's oversubscribed and people do not understand that the car has a 3rd, mostly underuntilized, state of neither pedal depressed (ie "coasting") ... so they create cascading braking pileups ...

To be fair, some (automatic) vehicles have such tall gearing that coasting will not slow you down if on a flat, let alone downhill. I've driven a few, and I can't stand them. You have no choice but to tap brakes.

I much prefer cars with short gearing for better engine braking. I continue to choose to drive a manual party for better engine braking.

If everyone that had it turned adaptive cruise control sigh.

So many people don't even use regular cruise control. They'll have nobody in front of them for miles and their speed yo-yos between 60 and 65 mph. And if you pass them because your cruise is set at 66 mph, they'll speed up to match, but then eventually decide to pass you, get in front, and slow back down to 60. The only way to end the stupid cycle is to go 70-75 mph until there's at least 1/4 mile between the two of you.

and there is a huge overlap between those people, and those who slow down to 60 to save on fuel.

If they'd just drive 70 on cruise control, they'd be faster, less traffic jams and less fuel use...

I really would like to see some mandatory use of cruise control on some stretches of highway, even if just as an experiment

The adaptive cruise control in my Subaru rarely coasts. It isn't smart enough to see a gap slowly narrowing and start coasting, and it isn't confident enough to temporarily allow the gap to be smaller than the setpoint while it coasts to recover the gap. So it brakes and wastes energy, and I don't use it.

Truckers sometimes have a good reason to do that -- they can't brake or accelerate as quickly as a small vehicle, and thus can end up going very slowly if they stick with the right lane. To a driver going 3 exits down the 205 it's not a big deal, to a truck driver doing the same they may be at the end of a long haul up the I5 and every minute starts to count since it can affect their pay. And if you can avoid hard braking/hard acceleration in the right lane, that can help your fuel costs quite a bit since slowly coasting behind someone doing 5 under in the left lane is more efficient than jerking around in the right lane.

There are plenty of ramps on I5 and 205 that I merge to the left for because I know they will spill into the right and (when it exists) middle lanes. Because of how traffic also reacts to brake lights (some people brake too hard even when they have sufficient distance to let off the gas and coast to a slower speed) it seems like it ends up making my experience through those stretches a bit better.

Ultimately, any individual behaviour is largely irrelevant, it's what the whole mass of cars moving along does that affects things the most. Often you don't want to be the (significantly) odd one out regardless of the situation.

That's not a good reason, those truckers are just assholes. I'd like to see the authorities enforce the law and fine them heavily. Put them out of business.

Being a bit more nuanced, I dont mind a trucker in the left in a 2 lane section (they're likely trying to avoid bad interactions with merging cars from the right) ... but it does bother me when its 3+ .

I've done a few tours around the world on the interstate system, so I've seen my fair share of truckers. Yeah, some are assholes, but there are stretches and routes where their behaviour makes sense, even if I don't like it. It's on them for how they behave, but understanding why they behave that way can make it simpler to deal with them in real life. As real, squishy people, not a system of rules.

Would I love to see CHP or OHP fine every left lane trucker in the 'no trucks in left lane' zones? Hell yes, but until that happens, I understand the trucker behaviour.

Driving a truck is more difficult than it seems. They are extremely heavy, very dangerous, be careful around them.

This is what most frustrates me about driving in Florida. The right lane is nearly always the fast lane, yet is the lane with most 'events.'

When asked, they'll say they feel safer in the left lane because they don't feel safe having to deal with people turning out and merging. So you get instead people driving fast in the lane meant for pulling out and merging.

>It's wild to me how often the left lane is not the fastest lane.

Reasons vary, but a lot of the time it can be explained by left exits/splits ahead on the highway. Which some may call poor design.

> as long as you travel in neither the leftmost nor rightmost lane

What I really hate, however, is that plenty of people will cruise in the center lane but still not leave a decent gap between them and the car in front. They effectively turn a three lane freeway into two one-lane freeways by hobbling the ability of anyone else to switch lanes. The freeway moves way smoother when there is a modest, predictable speed differential between each lane so that people can find their way into the next lane over without having to force the issue.

But you’re not getting slower and slower for every car. Lets say 100 cars pull in front of you, and let’s be say each car adds 5 metres of space, so you have 500 metres of ‘lost’ space to regain.

At 30 mph how much later will you be? 37 seconds.

I’ll take that trade.

> let’s be say each car adds 5 metres of space

At over 100 km/h that would be ideally 5m for a car and 70m for a safe distance between each one so 7,5km, which is 4.5 minutes at 100 km/h or 9 minutes at 30 mph.

Someone else is taking your safety buffer as an opportunity to travel at all.

This exemplifies the problem with America. People will cut off their own welfare to make sure their neighbor doesn't get any either.

That is a paranoid-survival oriented perspective.

> someone is taking your safety buffer as their opportunity to travel faster

Nobody is 'taking' something; we're all just sharing the road, and at little cost. People change lanes for many reasons, and sometimes to pass someone else and travel faster. That's what the left lane (if we're talking about the US) is for.

> results in you having to travel slower and slower to maintain the gap that is constantly consumed,

I understand the theory but that hasn't happened in my experience.

And even if five or ten cars got in front of you, how much distance is that? A random Internet site says the average midsize car is 16 feet; add 220 ft safe driving distance at 75 mph (says another random website), so let's say 240 ft per car x 10 cars is 2400 ft. In that extreme circumstance, it will cost you ~30 seconds.

It's self-fulfilling: If you act aggressively toward other drivers, they will respond in kind. If you treat them respectfully and politely, they act the same way toward you. People behave well and kindly, naturally. We are social creatures.

> as their opportunity to travel faster

You're ascribing motive where you have no data to do so.

> travel slower and slower

Roads near capacity slow down. This capacity surge is typically highly predictable.

> tragedy of the commons style, by opportunists.

People can only drive one car. They cannot drive two at the same time to get there twice as fast. I don't think this logic applies.

It brings me peace to see other people thinking this way. You should be an active participant on the highway, making decisions to maximize flow. Leaving space so people can merge, controlling speed to smooth slowdowns, anticipating traffic patterns, etc.

All of the people tailgating are contributing to the congestion.

https://youtu.be/iHzzSao6ypE

The trick I keep in mind in situations like this is to look at brake lights ahead of me. If cars are braking and I'm accelerating, I'm probably going to end up driving very inefficiently. By letting off the accelerator, I don't close the gap as quickly, and eventually, the turbulence in the traffic flow steadies out. Instead of stopping and starting, I roll at an averaged out speed, which doesn't feel as frustrating (it's kind of relaxing) and is better for fuel economy. There are, of course, the weavers who jump from gap to gap, tailgating and pushing. Sometimes it works, sometimes they just get jammed up.

I don't drive as often as I used to, but on I-76 coming into or out of Philadelphia, traffic gets snarled and becomes stop-and-go. Every now and then, someone next to me appears to have the same understanding of fluid dynamics as I do, and we build up enough of a buffer that we are able to eliminate the stop-and-go, even if it means rolling at 5mph with a big gap between us and the cars in front of us.

There's no good way to communicate what we're doing, even to each other. But I like to think that when this happens, it has a positive effect that ripples out for miles.

> I roll at an averaged out speed, which doesn't feel as frustrating (it's kind of relaxing) and is better for fuel economy

Yup. The brake pedal is an evil device that converts cash into brake dust and waste heat. Before I got an EV, I always drove in such a way to use the pedal as little as possible. As a result, in my previous car that was stickered at 24 mpg city/30 mpg highway, I averaged 32 mpg. I don't even drive slow, I just drive smoothly. If your average speed is going to be 5 mph, then you'll get much better economy driving a constant 5 mph than your speed being a sine wave between 0 and 10 mph.

76 is the worst

Funny that I could guess that the link would be to that CGP Grey video :D

Adam Something has a video responding to it that's worth watching too: https://www.youtube.com/watch?v=oafm733nI6U

"Turning urban areas into obstacle courses for pedestrians" was an excellent way to phrase that problem!

> making decisions to maximize flow

Good driving instructors make you aware of that early on, at least mine did.

I'm not saying that I'm a good driver, because I make mistakes like any other driver out-there, it's just that I oftentimes go with the "maximize the flow" thing instead of just following my individual "well-being" as a driver as a result of what my driver instructor told me some years ago.

You know very well that normal lane changing isn't what the person you're replying to is referring to.

The problem isn't merging, it's people that are changing lanes to get ahead.

It's especially not people trying to get off the highway because then they leave and you can catch back up to where you originally were.

> I will never understand why this is so rage-inducing for people

Putting my armchair psychoanalyst hat on: I think American society embeds a need to be the "winner", and are you winning if end up behind another driver who's contending for "your" spot?

If you've driven elsewhere for a while, you start noticing subtle driver differences, such as drivers who want to merge into your (slower) lane never braking to merge behind you and always accelerating to do so, even when you're at the tail end of a vehicle chain in your lane.

Driving in Melbourne -- I won't generalise to the wider Australia -- is often much the same.

Comparing to the experience of being a passenger on a bike in Saigon, the level of cooperation there is way higher, possibly due to a sort of necessity. I had this feeling while observing traffic there, that, while the latency and throughput of the roads during high traffic times are still kinda awful, at least for bikes there's a slow continuous progress that simply wouldn't exist without cooperation.

Funnily enough, my experience driving in Los Angeles was distinctly not terrible. Traffic was usually good enough to drive in, though there was very little regard for the speed limit on the freeways! I suspect I may have just been lucky to miss the worst of the traffic.

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I'll tell you what I specifically and intentionally do when I need to change lanes. I brake slightly, signal, and wait for the person on my right or my left to pull ahead of me, then change lanes immediately _behind_ them. Then sit there for a moment until my following distance evens out a bit.

This ensures that

a) I do not cut anyone off accidentally, and minimize the amount of stress in my immediate part of the universe

b) I will (most likely) have plenty of room behind me after I change lanes, reducing chances of anyone else running up on me

c) If there's noticeable traffic, the time I spend signaling and waiting for the person to move slightly ahead of me gives plenty of warning to the people _behind_ them that I'm about to enter the lane.

Ultimately, yes, of course in principle you're right, when I change lanes, I enter the lane in front of someone.... but I _can_ control whether I enter as far as possible ahead of them.

You shouldn't be braking when changing lanes is what I was taught, you should be matching the speed of the lane you're merging to. There are many drivers who think that braking is always the right solution, when sometimes it's a little more gas.

And in inclement conditions, it can make the difference between losing control of your vehicle or not. When you brake, you decrease your steering ability in most cars. Fine when its calm and sunny in CA, not so much when it's icing over near Ashland OR on the pass.

Well, sure - braking is mostly relevant when merging to the slower lane, when merging to faster lane I generally do not need to - since that lane is already moving faster, just need to speed up slightly and time it for the right moment.

My point is, it feels safer and easier to aim to enter a new lane with the aim of "following" someone, rather than trying to rush in "ahead" of someone. But maybe it's just me.

It's considerate communication. Lurching into the next lane .08 seconds after the blinker first flashes says things like "Your life isn't worth the basic consideration and respect of communicating my intentions" and scales up to "I'll communicate, but you're not worth any sort of common courtesy" - that can be upsetting to people.

It doesn't even have to be real. There's huge room for miscommunication. Unpredictable movements and perceived aggression, or unwillingness to be considerate to other drivers on the road, there's a whole wealth of information being processed, regardless of how little is actually real.

Now add the total lack of accountability for the driver's emotional state (don't you love yelling at other drivers, completely free of judgement?), and you can see how things spiral into road rage so relatively easily, even if everyone involved is normally a pretty chill, rational person.

If you're tailgating or brake-checking, or being inattentive and sloppy, you're basically threatening people's lives with a few tons of high speed metal, even if you don't intend that at all.

Ideally, the rules of the road are meant to reinforce a mutual understanding of the game being played. Behavior occurring when expected, proper signaling, observing limits, and making the effort to communicate where possible is a signal that you and the other driver are both operating by the same set of rules, giving you both confidence that neither of you are going to be a danger.

I've seen little "cute" exceptions where locals develop a subculture of dangerous assumptions and then get aggravated when someone from out of town doesn't immediately get it. There are other areas where aggression and what amounts to flagrant disrespect are the norm, so you've always gotta be adaptive, but ideally you get people conspicuously following the same set of rules as a sort of game theoretic optimal strategy for driving.

It's frustrating when it eats into your safe following distance. The driver merging in ahead of you is being dangerous and not leaving a safe following distance for themselves (or you).

When traffic is heavy, everyone is likely following at [what they perceive to be] a minimum following distance.

It's simply not possible to merge during heavy traffic without eating into someone's safe following distance.

The buffer exists to be used. Allowing people to merge into it makes the lane that they came from safer. Build a new buffer.

It takes almost no effort to restore your safe distance again.

What's the problem with reducing speed and reclaiming a safe following distance?

Might depend on your location, but usually you are legally required to allow a merge. Which makes sense, the system stops working when two lanes that are required to merge, don't merge because people are being petty and entitled.

> I will never understand why this is so rage-inducing for people.

The train of tought goes something like this. You want to get to your destination quickly as just like everyone else and are doing everything correctly, but the assholes exploit that safety distance as a gap available for them to switch into and repeatedly forcing you to break to maintain a safe distance. Oh and the even less rational people think everyone overtaking them has stolen their rat race position.

Leaving a keeping a safe distance feels unsafe since other drivers will squeeze into it. Subjectively it feels safer to close the distance, but the numbers don't lie. Tailgating kills.

If you think highway driving requires hard braking, you're a bad driver.

Yes. If people are constantly moving into your appropriate head way this is doubtless annoying but the correct response is allow yourself to decelerate slowly to re-open that space again, repeat as many times as necessary, even if it means a bunch of agros end up in front of you. Better for them to be in front where you can see them, than behind or to the side, were you can't.

Yah. There's something that feels unjust about it -- the perception that the people cutting are getting something over on you -- that causes us to want to behave badly.

But even if 2 dozen people go around you and creep into that following space, you've been cost like 45 seconds at worst. Better not to play the game.

Also, it really doesn't happen that often. I'm that guy following at 3 or 4 car lengths in rush hour traffic and people aren't constantly funneling in front of me. It's a hypothetical "problem" that is bigger in your head than in reality.

Sometimes I think it's just people's reflexive scarcity mindset that tells them "that spot must not be that desirable or someone would be in it."

Regarding the broader topic of hitting your brakes, I find that I can commute 20 miles in stop and go traffic and only tap my brakes a couple of times. Helps to pace yourself behind the car 3 cars ahead of you instead of the guy right in front of you.

I'm that guy following at 3 or 4 car lengths in heavy traffic an people are constantly funneling in front of me, all to go exactly the same speed they'd be going if they were behind me.

Society would have a lot fewer car accidents if we, collectively, could get over that "Oh no someone dared to get in front of me!" feeling.

We'd also avoid a lot of accidents if we stopped the people that are doing lane changes for position-jockeying and no other purpose.

So it's bad to be mad while driving, but there's a lot of lane changes that deserve the ire. (It's a tiny fraction of drivers that get really bad, but a less tiny fraction of lane changes.)

Being angry at them won't change their behaviour, but will make you more stressed. Remember: driving like that is its own punishment, because they'll be extremely angry and frustrated at everything. Between that and the realisation that driving 2% slower adds about 1 minute more per hour of driving you have to do, I find I can avoid stressing at people lane weaving and have a nicer journey myself.

> Being angry at them won't change their behaviour

Yes, but the comment above was about society collectively making a decision, so that's the context I responded in.

And while it's relaxing to not worry about your own exact speed, I don't see how that lets you avoid stressing about the people that are lane-weaving. They're acting dangerously and I need to be ready to react to them.

Unless they careened into your vehicle while making the lane change, just calmly allow your vehicle to drift away from theirs until you have a safe buffer again, and take joy in the fact that it didn’t meaningfully impact your arrival time, but you’ve meaningfully impacted the safety of your immediate surroundings.

How about you let the police do the enforcement, and focus on your own driving?

I already do nothing about it when driving, so no changes needed there.

And the police don't enforce this.

They are likely getting more frequent brake pad replacements.

Not a significant cost. But they sure as shit aren't getting what they think they're getting. Meaningfully farther ahead.

I now see it all as a risk assessment rather than as ritualistic combat.

If you added a missile launcher to your vehicle, it could become ritualistic combat again.

I try to maintain a constant speed in traffic, even if other people are speeding up and slamming on the brakes around me. Something like the average speed of traffic. Slamming on the pedals isn’t going to get you there faster.

Even if I do need to brake, speeding up more slowly also usually means I have more buffer time to slow down too.

This algorithm is garbage because it puts no value upon the danger cause by other traffic changing lanes when they would not have otherwise.

You're just going to wind up being approximately the slowest person on the road, which is fine if you're constantly trying to go slower to build space but this means that a bunch of traffic that would have not gone around you will do so. This ups the danger vs a steady flow less all these lane changes because every "thing" other people do is an opportunity to do it badly.

Kinda ironic when you consider that TFA was about detecting dangerous merge situations in the data.

Drivers could change lanes safely if everybody wasn't tailgating.

Absolutely agree. I take it a step (probably too far) further and think if you’re breaking on the motorway at all, you’re a bad driver. Ok, sometimes you have to, it’s chaotic out there, I get it. If you’re paying attention to actually driving your two ton killing machine you can drive for 200 miles on a motorway and not touch the break once.

Rounded to the nearest whole percentage point - highway driving is 0% braking.

I just had to hard brake a few days ago. A driver a couple lanes over on 101 slammed on their breaks, rotated 90 degrees, and came to rest across a couple lanes (one of which was mine). Fortunately, I was alert, driving the speed limit, and in the right-most lane, with nobody following me close. The whole thing happened in less than 5 seconds.

If you do it on the regular, or even occasionally, sure, but emergencies are emergencies.

Or stuck on a highway with bad drivers. My local paper's current "bleeds => leads" story is about a head-on highway crash, between a big pickup truck and a wrong-way driver. Less that 4 hours after being posted, that story has already slipped off the front page.

"local drunk dies by misadventure" is a really, really boring news article.

I'm not sure the article, the article being off the front page now, or driving with bad drivers has anything to do with it.

The article stuff definitely doesn't.

Driving with bad drivers should incentivize you to follow less closely and require less hard braking, not more.

There's a motte where some poor fellow is always maintaining the car-length-for-every-10-mph rule and yet keeps being passed inside that distance by innumerable bad drivers the fellow is surrounded by.

I pity that fellow.

He has an excuse.

He also isn't observably real in any of my 21 years of driving in Buffalo, Boston, and Los Angeles.

I feel harsh for saying this, I am only saying it because A) this subthread is specifically about there isn't an excuse B) this stuff involves our lives. Thus, this is an appropriate venue because the people in the venue know what to expect, and poking at someone's thoughts on it may help them immeasurably.

It doesn't normally require hard braking, but when automated emergency braking decides to slam on the brakes at random for no reason in my own car, everybody behind me will share my resulting insurance rate increase.

It's almost as if the purpose of the system is what it does.

If you think people are going to cut in front of you, provide a safety cushion large enough to account for that. Aggressive drivers almost universally will consume the forward part of the space cushion you leave. At most you will simply need to lift the accelerator to maintain space. The only time someone cutting in front of you should require hard braking is if they also brake hard.

It does require patience to do this, because all aggressive drivers will use the space you provide. But ultimately the travel time difference in flowing traffic is negligible.

I'm not sure it's that negligible. Mythbusters found that weaving in and out of traffic could save between 5 and twenty-five percent. Now A) Mythbusters did an experiment with an N of like 4 or something, along a single commute in the Bay Area, so it's basically anecdote and I'd love a better source if one existed, but it is at the very least proof-by-existence that larger impacts on travel time _can_ happen. And their non-weaving person was, if I recall from the video, not constantly decelerating to keep a buffer.

And from personal experience in some places, keeping such a buffer, in some traffic conditions would just literally be impossible. There are sometimes enough aggressive drivers such that they can just consume it faster than one would be able to create it. It is simply not always the case that you have sole power to create and keep the recommended buffer size (although very often it is and you can).

I keep a decent buffer whenever I am able, but at some point, you have to bow to road conditions.

25% of time saved corresponds to increasing your average speed by 1/(1-0.25)=33%, for example from 45 to 60.

Letting a large fraction of the freeway cut in front of you will turn normal drivers behind you aggressive, or at least aggressive enough to go around you. There's a balance to be struck.

Oh no! Cars will go around you!

Cars making aggressive maneuvers around you is dangerous for you.

If plain old overtaking results in "aggressive maneuvers", you should not be driving a car.

The premise of this line of comments is that the other drivers are acting aggressively. Whatever you're picturing in your head is a different situation from what everyone else is talking about.

In your haste to be snide and look down your nose what you've ignored is that this interaction is not "free".

Traffic moving with an approximately constant following distance is safer than traffic where one element is constantly traveling under speed to build up a following distance and is slowly filtering to the back as traffic comes upon and then moves around it. If the lane people are pulling into for passing is traveling substantially faster than the traffic that is being queued up behind to be passed then some amount of the people pulling out to pass are necessarily going to do so aggressively or within thinner than "perfect world" margins.

Every thing drivers on the road must perform carries some inherent risk. That a bunch of traffic that would have not gone around you will have done so means that many otherwise unnecessary merges or lane changes and then lane changes back will have happened. Each one of these represents an opportunity for things to go wrong above whatever the baseline is.

What I am saying is not groundbreaking or rocket science and the fact that I have to spell it out in detail to an adversarial audience speaks volumes about this audience and the volumes it speaks are not positive.

Tailgating is against the law. Tailgating causes hard braking.

I recently pulled my travel trailer from OK to Charleston, SC and back. I never drive over 65 MPH for safety and MPG reasons. I always stay in the right hand, slow lane except if I have to take a left lane exit. Since I was always driving slower then everyone else, not once did I have to hard brake. Tailgating is a choice and a dangerous one.

I was never honked at, even by the crazy semi truck drivers.

>I was never honked at, even by the crazy semi truck drivers.

Because you were towing a camper and "slow and in the right lane" fits people's mental model of how recreational/nonprofessional heavy traffic or otherwise "handicapped" vehicles ought to behave.

When you have problems is when you behave to a standard beneath what other people expect from whatever kind of traffic you are.

In the Atlanta area I've experienced a few times people FLYING up on me in the right hand lane while I'm cruising along at a conservative, gas sipping 55 MPH in my old truck, blaring their horn at me like I'm some kind of maniac.

I don't want to live on this planet anymore.

Driving and living in Atlanta after living in Charleston and Raleigh felt like transitioning from a modern cooperative society to an island of cannibals. The amount of aggression needed to change lanes largely regardless of attempts to signal good faith and politeness is baffling. Driving is a fascinating ritual with vastly differing norms across regions. It would be interesting to learn if anthropologists have studied this

> Driving is a fascinating ritual with vastly differing norms across regions. It would be interesting to learn if anthropologists have studied this

And Psychologists!

Reading the comments in this thread is quite amusing.

As a driver in India, i can tell you anything goes as long as you don't get into an accident (which may/may-not kill you) or get caught by the police.

No rules matter and the only goal is to "one-up" everybody else on the road and if they are trying to "one-up" you, then prevent it by any means possible. It is a "game of chicken" in its purest form; game theory in action. Rules are mere suggestions only followed by the meek and the weak.

You have no idea how invigorating it is to drive in India.

> No rules matter

I was only briefly in India and did not drive while there, but the one rule that everyone adhered to was: communicate what you're doing by honking.

If you are stopped: honk to let people know.

If you are moving: honk to let people know.

If you are turning: honk to let people know.

If you are proceeding straight: honk to let people know.

If you are on a motorbike or in an autorickshaw: honk twice to let people know.

Etc.

I don't mind that sort of traffic, as long as I'm in Somebody Else's Car or an old junker that's already banged up. In these situations, the biggest and ugliest car/truck with the meanest driver always wins.

Addendum:

Drive in India and you will understand mathematical concepts of Chance/Randomness/Probability/Non-determinism/Game Theory/etc. along with philosophical concepts of Fate/Destiny/Providence/etc. in so direct and visceral a manner that you will never forget the lessons. Sissified countries with rules and regulations for driving can never give you such direct knowledge.

Game Theory - https://en.wikipedia.org/wiki/Game_theory

Game of Chicken - https://en.wikipedia.org/wiki/Chicken_(game)

The game of chicken models two drivers, both headed for a single-lane bridge from opposite directions. The first to swerve away yields the bridge to the other. If neither player swerves, the result is a costly deadlock in the middle of the bridge or a potentially fatal head-on collision. It is presumed that the best thing for each driver is to stay straight while the other swerves (since the other is the "chicken" while a crash is avoided). Additionally, a crash is presumed to be the worst outcome for both players. This yields a situation where each player, in attempting to secure their best outcome, risks the worst.

How to learn One-upmanship/Gamesmanship:

The British author Stephen Potter actually wrote a manual on the practice of such games titled The Theory and Practice of Gamesmanship (or the Art of Winning Games without Actually Cheating) which sissies can study to become strong - https://en.wikipedia.org/wiki/Gamesmanship

For the even more sissified sissies who do not want to read a book, there is a documentary titled School for Scoundrels Or How to Win without Actually Cheating) which is very instructive - https://en.wikipedia.org/wiki/School_for_Scoundrels_(1960_fi...

Disclaimer: I am not responsible for the consequences if the above emboldens you to act in such a manner in your specific context.

India is working to fix that. It is slow going, but things have improved over time, and police are enforcing driving laws (at least in some areas)

That's easy to deal with: They're behind you. Ignore them.

Setting the side mirrors based on the AAA method works for a lot of reasons, and it helps with this too. So does flipping the center mirror over to the dark side.

Out of sight, out of mind.

They can be elect to stay back there behaving however they want, or they can go around be however they need to be somewhere else.

If you just can't stand it anymore, then just hop off the highway. It can be a good opportunity to stop for some coffee or a soda. Or, you know: Just to get out of the car, stretch out the ol' legs, and taste that acrid city air, think about something or someone in the world that is beautiful for you, and chill down a second.

Or just go up one exit ramp and down the entrance ramp on the other side of the crossroad, if the intersection design allows this move to be made safely and conveniently.

They almost certainly won't follow. They'll instead be disappearing down the highway at warp speed the whole time you're doing this, and you'll probably never across them again in your entire life.

It only costs a few minutes. They may seem interminable, but they're few. The benefit is relief from the mounting agony of dealing with this aggressive driver that might otherwise stick with you the rest of the day and that's good for your brain health.

(And if they do follow after you give them every opportunity to not do that? It's not Hollywood or the national news and this actually doesn't happen much in the real world on an individual level, but: Call the police at 911 or 999 or 0118 999 881 999 119 725 3 or whatever it is, and get some help.)

It's all fun and games until one gets rear-ended by one of these mental patients.

The solution is just to stay out of Atlanta, or drive faster. I'm OK with that.

Not really sure where you were going with all this. Sounds like pretty extreme, weird behavior that you are advocating.

> Sounds like pretty extreme, weird behavior that you are advocating.

Advice for when someone is following closely in anger that summarizes to "try getting off the highway for a minute and if that fails call the cops." is suggesting you perform "extreme, weird behavior"? I don't understand your reaction at all.

The people in question weren't angrily following me. If that were the case, there's no need for any theatrics.

The first weapon to be employed is a Middle Finger. If that proves ineffective, it's followed by a lugnut taken from a coffee can that I keep handy. If and when things get to that level, the person usually wises up quick and finds a new hobby. There are other tools available if the nutcase decides to escalate further.

No, in this case it was just people speeding along at 95 (in a 70) who were terribly offended at my dangerously slow driving, who wished to register their indignation as they flew by, momentarily held back but undeterred as they sped off to their Bright New Tomorrow. Message received, loud and clear.

So just... let them go. It's easy to do.

Escalation usually doesn't improve things, including for the person displaying the universal finger (or throwing the lug nut).

You've got a choice: You can keep plodding along in your truck while you escalate and retaliate and get all grumpy and stuff, or just keep plodding along in your truck without any of that noise.

The errant, instigating driver won't really learn anything either way.

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Prisons are full of people who are sure that they were right.

Like the prison you live in, for example.

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> The first weapon to be employed is a Middle Finger. If that proves ineffective, it's followed by a lugnut taken from a coffee can that I keep handy. If and when things get to that level, the person usually wises up quick and finds a new hobby. There are other tools available if the nutcase decides to escalate further.

I, uh, okay but I hope you realize that this is far more extreme than what the other person was suggesting!

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Taking a break is less extreme than throwing a lug nut at a moving car.

Exiting and immediately reentering a freeway is also less extreme.

Calling the cops if someone that is raging at you follows you when you do that is not extreme.

Nobody suggested "driving all over creation".

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Because I refuse to... throw stuff at people?

And are we in different societies now?

Yes.

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Even that can be tricky, with the indecisive behavior people use when merging.

That one's easy: leave space in front of you for those merging onto the highway.

So much of road etiquette boils down to leaving adequate space so others can maneuver around you. Trying to optimize your travel by destroying any gaps as soon as they appear actually has the opposite effect.

James May calls this "Christian motoring". Golden Rule etc

While leaving space is nice, the person on the highway already typically has right-of-way.

It's really not. I drive at an upper-percentile pace, so I am rarely dawdling along in the right lane.

However, on the rare occasion I've found myself going slowly in the right lane, it's stunning how incompetent most people are at merging. It's like they don't even consider looking for an opening in traffic, matching the freeway speed, etc. They just lumber in front of you at 43mph, and maybe, if you're lucky, look in their mirrors after they've already caused you to slow for them.

Very true and it's the reason I will always leave several car gaps in front of me in heavy traffic. Just because I have electric brakes on my travel trailer, it doesn't mean I can slow down normally, they just assist. Most people really don't think about that, of course, so they ignore the trailer and just weave in and out.

Speed is a very dangerous thing when pulling any type of trailer and it always amazes me when I see a truck pulling one at break neck speeds and somehow thinking they can maneuver normally when someone causes a situation where they have to make a split second decision.

I'm one of the faster drivers and I maintain a safe distance. (I usually have the most distance in rush hour.) It's very easy with adaptive cruise control or the other self-driving technologies that are on the market.

The only people who cut too close to me are driving recklessly.

That being said: If you're in the mode where people are constantly changing lanes in front of you, think a bit about how you're driving: On the freeway you're supposed to stay to the right except to pass, and you're expected to keep up with the flow of traffic. Are you going slow in the left lane? Are you driving too slow? Are you camping in the right lane by a busy interchange?

> and you're expected to keep up with the flow of traffic.

This is very state dependent, if we are talking about legality.

In WA state, for example, there is no "flow of traffic" law or similar. The limit is the limit, and any excess of the speed limit is illegal regardless of what all other drivers are doing. So even if the right/slow lane is going 100MPH through the 70MPH zone, you are legally expected to still go 70.

Thankfully we do have laws against left lane camping, but I rarely see it enforced.

> This is very state dependent, if we are talking about legality.

Are you sure? And by that I mean, are you sure there are states that don't work the way WA works?

You’re confused. If you know of ANY US state that has a flow of traffic law that allows cars to exceed the speed limit so long as they are keeping up with other traffic, I’d love to see a link to their traffic codes. Speeding doesn’t suddenly become legal because two or more drivers do it together.

This has nothing to do with the expectation that slower traffic stay in the rightmost lanes, which is what GP is addressing.

> Speeding doesn’t suddenly become legal because two or more drivers do it together.

That's not true. Examples:

I once pulled out my local newspaper where local judges were petitioning to have speed limits raised because they were throwing out speeding tickets due to excessive fines. This was in Massachusetts, in the late 1990s or early 2000s, about a road in Shrewsbury near lake Quinsigamond. The context was that the speed limit was 25, traffic flowed at 40-45, and they would throw out tickets for people doing 50.

I was once pulled over in a Massachusetts tollbooth even though I was the slowest driver on the road. (2004, I90 westbound at the intersection of 128, when EZ Pass still had to go through actual tollbooths.) If I was given an actual ticket, I would have point-blank told the judge that I was going half the speed of everyone else and feared getting rear-ended; then the case would have been dismissed. (The cop also knew this, because he recognized me from traffic court and knew that I'd make him look like a fool for pulling over the slowest driver.)

In my place, there's a significant group of drivers who will ride your tail too close hoping you'll move over so they can get 1 car ahead. And if they see more than 0.9 car length in front of you they will do what they can (weaving other lanes) to try and get into that space, 1 car ahead of you.

As far as I can tell it's pure selfishness and competitiveness. Their desire isn't to cooperate and arrive it's to take from others for their own gain.

Also "Only pass in the left lane" only makes sense when the lanes aren't significantly full. The guy in the left lane wants to do 90mph but the average speed of traffic is <55mph. Should I move over just because I'm doing 55 (despite wanting to do 65) and they want to do 90? They can only do 90 if there's a cascading group of drivers in front of them who defer their own desires to the desire of the most aggressive. Seems obvious to me that moving over to let them pass is not the right move.

That's (the tailgaters) reckless driving and very illegal. It's a symptom of poor traffic enforcement.

I definitely agree there is poor traffic enforcement here. In fact our cops are basically potatoes.

This is accurate in many ways. I use the auto cruise feature on my car frequently and I notice several things happen unless I set the distance as close as possible (which I don’t like to do. ).

1. In any amount of traffic above “a few cars” people will cut in front of me, sometimes two, negating the safe following distance. Regardless of speed.

2. If I have a safe following distance while waiting for someone to get over. (I e they’re going 60, I want to go 70), if I have my distance set at a safe following distance, people are much more likely to weave / pass on the right. (My theory would be that the distance I’m behind the person in front of them signals that I’m not going to accelerate / pass when the person gets over ).

Disclaimer: I don’t usually have to drive in any significant traffic, and when I do (Philly, New York City), I’m probably less likely to use the automatic features because the appropriate follow distance seems to increase the rage of drivers around me.

I always wonder why so many people observe this when I never have. It makes no sense logically; it's the speed of the car in front of you that determines whether they should switch lanes, not the size of the gap behind it. There is no reason for them to cut in when your lane is no faster. Perhaps you are just the sole person leaving enough room for people to execute needed lane changes.

At any rate, even if people are continuously going around you like water going around a rock in a stream, you only have to drive 2 mph slower than traffic to constantly rebuild your following distance from the infinite stream of cutoffs. But my experience is the majority of following distance is eaten up by people randomly slowing down, not cutting in.

In the auto cruise example, it’s leaving perhaps 2 - 2.5 car distances. In close traffic the average human I would bet is leaving 1 or less then 1.

The issue is not that I can’t rebuild the following distance, the point I’m trying to make is that even if I constantly rebuild the following distance it sets off a cascading effect.

I’m following at set speed, car cuts in front, hits brakes, I now slow down, car behind me slows down, I rebuild following distance and car perhaps 7-8-9 cars behind me repeats because at some point the cascade magnifies to a larger slowdown behind.

Can I mitigate this by manually letting my distance be closer for a time, and slowly easing to larger ? Yes.

But if I allow the car to do it automatically, it will increase the follow distance at a rate that causes a cascade in tight traffic.

Though - I do think with these discussions on HN- it does depend on where you’re driving.

My experiences are centered on East Coast, thinking of route 80, 81, 83, etc. or Philly / New York City.

The driving experience is radically different in California, Florida , or the mid west.

I would say when driving in California people seem to navigate traffic better. (SF, LA) then on drivers on 80/81/83. (Or perhaps it’s due to better designed roads ).

> In the auto cruise example, it’s leaving perhaps 2 - 2.5 car distances. In close traffic the average human I would bet is leaving 1 or less then 1.

At 60 kph (16.7 m/s) 1 car distance (about 5 m) is less than one third of a second. Even 2.5 car lengths is less than a second. I use traffic aware cruise control on my Tesla set to the maximum separation which is about three seconds, so 50 m at 60 kph.

Three seconds separation is in fact the recommended following separation in most European countries and in Germany in particular 0.9 seconds or less can result in a hefty fine, see https://en.wikipedia.org/wiki/Two-second_rule

In the UK some stretches of motorway have chevrons marked on the road indicating the required spacing at the speed limit.

3 Seconds is also the recommended following distance in the US. This is a change from when I took drivers training when 2 was recommended.

Almost nobody follows it, but that is what the rule is.

Just drive in the slow lane and you won’t have this problem. The people cutting in front of you rarely want to be in the slow lane.

I do drive in the slow lane frequently - and this still occurs. (My go to is to set my cruise 6-9 mph over the speed limit, if passing to smoothly pass and get back over, and spend as much time as possible in the slow lane. )

However - I will say most of the roads I’m on are 2 lanes of traffic. I will have to experiment and see if this doesn’t occur when there are 3 or 4 lanes.

The idea of cruising 15km/h over the limit is absolutely crazy to me. That will get you 3 points and a minimum $500 fine here. We have "average speed zones" too!

There are different norms in the U.S. - where I am- generally 5 mph over the posted speed on side roads, and ~9 over on interstates / highways.

You are very unlikely to get stopped for either of those.

Another commented using an example of 8 and 9, but here it’s “9 you’re fine, 10 you’re mine”.

Where I live travelling at that speed will get you passed by every cop and state trooper driving on the same road. A lot comes down to local norms and enforcement.

In Alabama on the interstates and highways the rule of thumb is: "8 you're great, 9 you're mine."

> I do drive in the slow lane frequently - and this still occurs.

One part of your post was about people passing on the right. People won't do that if you're in the rightmost lane.

Apologies - you’re correct. I should have been more specific in that I was referencing the scenario of:

I’m car 2, waiting to pass car 1. (Who’s passing a car slowly ). I have safe following distance.

Car 3, passes me in the right lane, and then either follows car 1 closely, or, quickly passes them on the right. (Usually as they’re in the process of moving over, causing them to then swerve back).

I realize I communicated this in an absolutely abysmal fashion.

Well, if there is an emergency lane to the right... it actually happens quite a bit around here.

In Southern California the "fast lane" is the medium speed lane, and the "slow lane" is the actual fast lane. It's where people tend to weave in and out of traffic at 15-25 mph speed differentials.

I don't know you can find that traffic always bunches up. And if one is content to sit in the gaps in between, almost never anybody cuts in. I drove twice 1000 mile trips each way last year and it kind of worked. It's more of a mindset than anything else. Fastlane is not that fast or it would be empty, lol.

The fast lane isn’t always faster is very true! Haha

What I will say is some of this may be the difference between manual driving - and automatic.

If I’m manually driving - where my follow distance fluctuates more due to speed / traffic - almost no one cuts in.

If I am driving where I’m using the vehicle to maintain a perfect set distance, people cut in.

Again, anecdotal

This was part of the training materials of one bus driver I knew. When people continually take that gap and you continually have to back off, it only adds a negligible amount of time to the commute.

> North America

Having driven all over NA, and Europe, I find it more prevalent in NA. Less distance, more people in large pickups throwing their weight around to make someone move out of the way.

And a design of giant freeway interchanges that require shifting lanes.

E.g. on the 405 in CA. 7 lines going South from the Valley towards Santa Monica.

That's 7 lanes you need to cross if you're in the HOV lane.

> That's 7 lanes you need to cross if you're in the HOV lane.

The 401 is my favourite with eighteen lanes, four for the inner express lanes, and five for the collector lanes.

https://en.wikipedia.org/wiki/Ontario_Highway_401#/media/Fil...

Honestly imo the driving license requirements and the respective fines for violations is too low. Rigid rules generally improve the traffic flow. But as soon as someone just doesnt care, the system breaks down.

I live in a place that has harsh winter conditions with ice, gravel and the occasional loose tire stud flying into people's windshields, warranting frequent expensive replacements.

Somebody on the radio said that "just set the adaptive cruise control to max distance and your windshield will last way longer". It does feel overprotective at times, especially in slow and dense traffic, but I think there's a nice point in general.

Wow, I didn't know that was a thing. Been driving nearly 30 years, and never had a windshield chip.

Grow up in a place where roads have gravel on the shoulders and are made using coarse-chip seal and you’ll get them regularly.

Yeah, I imagine. I'm inner city.

Do you have a wood surface nearby? I would recommend giving it a good knock.

Apparently I just live in a place where it's not a common problem. Also I do tend to leave a big gap behind cars in front.

They salt your roads, or put grit?

They don't do either of those things, and yet somehow I haven't witnessed any cars sliding off the road in winter either.

From everything you've said so far, it sounds like people in your area have a lot of sense.

Also we don't get snow.

Yeah, that would do it.

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Another trick that works is just to let the windshield get cracked once. Then it will be immune to further rock strikes. Studies have shown that freshly replaced windshields are 937% more likely to be hit with a rock.

#trustmebro

#science

Does it really matter though? Is the end result just a couple of minutes later in a 30 minute commute? Or does it actually make a large difference in travel time?

> Is the end result just a couple of minutes later in a 30 minute commute?

More like a few seconds.

Every car that merges in front of you only costs you their following distance. If the average following distance is 1 second, then you are simply 1 second slower than you'd have otherwise been. So unless this is happening continuously every 30 seconds on your 30 minute commute, you will lose less than a minute.

The "but if I kept reasonable following distance, people will keep merging in front of me and I'll lose time" excuse is pretty thin given this analysis.

And an insurance claim can easily eat 40 hours of time between the insurance companies, other lawyers, buying a new car, medical appointments and recovery. That's 19,200 minutes you won't get back, or about 52 years of driving 1 minute slower each day.

Slow is smooth and smooth is fast.

It doesn’t - but people don’t necessarily make rational choices regarding speed and driving. There’s a tendency to de personalize other drivers.

A slight increase in average speed really only makes a significant difference over long drives. (5 mph increase over a 10 hour drive can cut off 50 minutes).

Otherwise we are talking about small differences in efficiency.

(I would be very open to another opinion here.).

My opinions are formed by nearly ~2 million miles driven at this point, two different driving courses, and the motorcycle safety course.

One thing I truly think that’s overlooked is how reduced road noise in the vehicle cabin can both reduce driver fatigue, but also frustration in traffic.

> A slight increase in average speed really only makes a significant difference over long drives.

Yes! I feel like I can't shout this loud enough. In addition to maintaining a safe driving distance, just leave a little earlier. The stuff I've seen people do in order to save 20 seconds boggles the mind.

Unfortunately, I think commuters fall into a gamification mindset. They're trying to set a new lap record each day, and you can see the results just by driving (or walking) during rush hour...

> (5 mph increase over a 10 hour drive can cut off 50 minutes)

You can't really say that without knowing the starting speed, or alternatively the distance. All you can say is that a 5 mph increase over a 10 hour drive with get you 50 miles farther.

I would argue I can still say it /can/ cut off 50 minutes.

If you do a comparison of a 600 mile trip at 60 vs 55 you’re pretty close.

But yes, to be pedantic and more exact, you are spot on that it will get you 50 miles closer.

But in real world examples,

If you’re traveling 700 miles.

65 vs 70, 70 will reduce your time by 43 minutes.

So in certain scenarios, 5 mph difference must be able to save you 50 minutes ! ;)

(I do understand your point, and you’re correct. I’m just poking fun at it- my point with the mph difference is because 50 miles doesn’t have the same translation for most people at 50 minutes, but is a more accurate data approach. )

> So in certain scenarios, 5 mph difference must be able to save you 50 minutes ! ;)

That is true. If you're going 55 mph for 10 hours, you'll go 550 miles. Increase your speed to 60 mph, and you'll get there at 9 hours 10 minutes.

It used to be more of an issue when I was younger. Now that I'm older and more 'seasoned' (plus reflexes do slow down), I'm far more patient and have no issue maintaining a healthy following distance. I think the statistics reflect this in age vs. accident rate as well.

Unfortunately, sometimes over a 45 minute freeway commute, dropping back repeatedly means arriving 15 minutes or more later. Again, no big deal now, but it was somehow unacceptable when I was younger.

For your commute to take 4/3 the time, you would have to be averaging 3/4 the speed -- going 45 in a 60. That doesn't make sense because even going 55 would mean traffic pulled away from you rather than you having to drop back from it. Going 55/60ths the speed means you arrive in 60/55ths the time, or an extra 4 minutes on a 45 minute commute.

I have been doing the same commute at the same time for the better part of a decade. At this point I can look at my watch and tell if I'm ahead of schedule or behind schedule and infer what the compounding effect will be later in my commute.

I can easily shave 10% off my commute by lane changing to avoid the lanes where turn lane traffic tends to back up into the travel lanes, ramp traffic and "problem people". I test the null hypothesis several times a month by carrying bulky topheavy cargo that precludes a bunch of lane changing without more effort than I want to put in.

I don't think there's much to be gained by simply lane changing to chase fleeting gaps in traffic. The wins and losses will probably mostly cancel out.

> vehicle changes lanes in front of you; you slow down to maintain a safe following distance, another car sees a gap and changes lanes in front of you. Repeat for your entire commute.

For the sake of argument, assume you follow the "three second rule" and that the other driver is slightly aggressive and enters closer to the front of your safety buffer. You are now down to a two second safety buffer so rebuilding it back to three seconds costs you an extra second of travel time.

In practice this happens to me about a dozen times a day. It sometimes feels frustrating, as if each of these drivers is stealing another second I could have been playing with my kids! But ultimately it's worth spending the extra seconds to slightly increase the odds that I arrive home each day to play with them at all.

Okay I'm thinking of a very Shenzen kind of gizmo for your car that projects a bright red laser "keep out" box on the road in front of your car which is adjusted in size for your current speed.

We have something like that in eu with road markings. Both for clear weather and fog/rain. They mark some of the lines differently, and tell you how many lines you should have between you and the car in front. I think they were first trialed and then printed in several places.

Cool. But I'm thinking this box floats in front of your car on the road in real time. See you're driving and ahead of you on the road is this box. At night it might interfere with your night vision, might have to workshop that a bit.

There's a couple of bits of motorway in England with that, I'm pretty sure the M6 and the M1. There are white chevrons painted on the road and you keep two of them between you and the car in front.

Also "Keep Two Chevrons Apart" is going to be the name of my specialist Citroën breaker's yard.

And on the M5 between Gloucester and Bristol.

I think a lot of people would just consider that a challenge.

On the occasion when I am towing our travel trailer, it is really incredible how unsafe that makes other drivers act around me. They will jam themselves in front of me at all costs, with no consideration for physics.

I see this happen to semi trucks on the highway. People interpret big open space as a place to merge. As you say, people have no consideration for why there might be a large space in front of a semi. A 50k lb+ truck hitting the back of a ~4k lb vehicle is not pretty.

See for a truck it could say "DEATH ZONE KEEP CLEAR" which would be accurate. Given that it's projected it could rotate through various languages too.

There was a bike light that projects a bike lane onto the road, not sure why they are not more popular.

Can't wait to get blinded by lasers when cars are going over bumps and speed humps.

I know you were probably writing tongue in cheek, but that is one of those "solutions" that doesn't stop bad actors and makes good actors more miserable than usual.

Like LED headlights :-). It would kind of be a concern except that geometry in in your favor. The angle down they would have to shine + the size related to speed would result in the lasers pretty much always hitting the street except perhaps if you were at the top of Gough[1].

[1] SF drivers will get that.

> another car sees a gap and changes lanes in front of you

Usually if you maintain the slightly slower speed you had to maintain a safe following distance it doesn't matter, as the distance will either increase or they'll leave for another lane. You have to get used to drivers doing messy things in front of you, but at a safe distance. When doing this you are in fact helping the traffic becoming more fluid.

I leave a lot of distance, but people rarely change lanes to get in front of me, because the person I'm following isn't going any faster; the separation is in d not v. Most people who do change in front of me are there only briefly on their way to an exit, which means I'm increasing the fluidity of the traffic flow, so I'm happy about that. If I didn't leave space, they'd likely hard-brake in front of someone, causing a slowdown.

I actually disagree.

People only take your lane if you are in the fastest lane. If you are in any slower lane, people tend to jump in and then leave and I have no problem with people who do that.

You can also keep a gap in the fastest lane but you need to keep track of other cars on the road. You’ll observe that most cars rarely leave their lane. People who tend to leave their lane keep smaller gaps in front of them. Use that knowledge. There are many more factors than just that but if you start observing everyone drive, your little simulation in your head will start putting other drivers into buckets.

These comments make me grateful that we have the concept of 'lane discipline' in the UK. It's rare to see the 'fastest' lane be anything other than the outside one. Otherwise we keep left and out of the way.

https://www.highwaycodeuk.co.uk/lane-discipline.html

Now try it with a heavy trailer, where you need even more room to brake and maneuver safely. People are just idiots.

I find it quite easy to hold/manage a tight space that people won't cut into, and don't have to brake hard, because I look ahead.

To be sure, it's more mentally taxing to hold a tight gap, so it's not something you want to do all the time, but it's fine.

gah YES.

I had a slow realization that I could just let people jump in. My goal is to maintain a constant speed and never have to hit the brakes, and I can usually still do that regardless of whether people jump line.

But yes, the principle of it is incredibly aggravating ("that space is for safety, not YOU, green Acura!!!") but I actually kinda like the practice of trying to be zen about it. I mostly get through a long trip at the same rate :)

Woah, like, "green Acura"? Where are you driving that you ever see one of those? In the USA?

I looked up an image catalog, and it seems that if an Acura's going to be green, it is likely to be an NS-X, which are fairly exotic as Acuras go.

I owned a black Integra for a while. If any had been green in those days, I would've definitely noticed! And, I definitely would've yielded the right-of-way to them, just so I could gawk and stare!

This almost always happens when you are in the passing lane, and you are not passing. It’s much more rare in the right lane. Mythbusters, and also other traffic studies, show that returning to the right lane on the freeway whenever possible adds almost no time to a trip.

> another car sees a gap and changes lanes in front of you.

it's largely a problem in the left lanes, thats where drivers will bunch up most. the subjective feeling is mostly a reptile brain issue though, the feeling you're getting done over. driving is 90% id, sadly.

Totally. People will just cut you off repeatedly, which puts you (and the cars behind you) in a less-safe situation than if you followed more closely.

> puts you (and the cars behind you) in a less-safe situation than if you followed more closely.

Really? All you have to do is lift your right foot very gently until you have the expected spacing again, no need to sudden changes of speed and if you have traffic aware cruise control it will be done for you. My old Tesla S does it pretty well. I keep it set to three second spacing and when someone cuts in front my car just gently slows down until the spacing is correct again; it doesn't brake unless the car that cuts in is very close.

I admit that I probably don't leave as much space as recommended, but I leave a good amount of space to never need to hard brake, and people don't keep moving in front of me either.

I find that respect for safe following distance varies quite a lot amongst the places I've driven.

E.g.

- Switzerland and (somewhat surprisingly) UK: pretty good, people doing idiotic shit is rare enough that I'll usually comment on it if there's another person is in the car. If someone is riding my ass I'll make the effort to try and shake them off.

- Italy and Spain: horrifying, impossible to relax at all on the highway, having someone 2 car lengths off your rear bumper is the default condition.

- France and USA: somewhere in the middle where there are a lot of idiots but they are still the minority.

Subjectively, the USA feels much more sketchy because the rules are so much looser around overtaking.

I think Belgium is the worst for tailgating but the French are pretty bad too.

False. I've done it many times - when you open up space two cars jump in, but the rest don't and so the space remains. But you notice those two cars and think it means more than it does.

> Maintaining a safe following distance is incredibly challenging on busy freeways

I just put adaptive cruise control on max distance and call it a day, gives me 4/5s to react, and also it starts beeping hard if intervention is required.

It has saved my bacon a couple of times.

Why does this require "hard" braking? If another car cuts in front of you just decelerate gently. You don't brake and wait until the gap is big enough (also if this is stop-and-go traffic, you should be trying to avoid braking at all)

My original observation wasn't worded as well as it could have been. I meant in situations where hard braking could be required on a moment's notice for no particular reason (e.g. Chicago freeways where everyone is doing 70 mph bumper-to-bumper and decreases to 10 mph all of a sudden).

Indeed, when someone changes lanes in front of me, I gently let off the accelerator, but as someone else noticed, that can enrage drivers behind me (I don't take it personally), and I'm definitely traveling fast enough to remain in the middle lanes.

Maintaining a following distance is going to be one of the things that improves dramatically once self driving cars are widespread. Self-driving cars simply don't care that someone cut them off, they'll just happily open up extra space again and again.

You don't need self driving, just traffic aware cruise control. Pretty much every modern car can have this as most now come with automatic emergency breaking and the same sensors can be used.

It’s not challenging at all. You leave the buffer. If someone sees the gap and merges into it, that’s fine! You always maintain the buffer.

It’s not hard to do. It’s only frustrating if you let it be. It really barely slows you down at all.

Doesn’t happen much in Portland OR, at least before the invasion of homelessness here. We had the most “nice” drivers in America.

The most frustrated people are those behind you, and if I was id soon be another person merging in front of you. If people are constantly merging in front of you, either everyone is going too fast or you are going too slow :)

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Safe following is super important. Few years back about a month after I bought a new car I was driving to work keeping a larger than normal gap thanks to a bit of "new car" anxiety. I was in the left lane, keeping pace with a cluster of three cars ahead of me, two of them tailgating. I don't know what happened but within seconds the middle car swerved, side swiped a car in the middle lane then rear ended the lead car while the trailing car rear ended them. Four cars smashed up right in front of me. I was fine because I had plenty of time to slow down and pull onto the shoulder to clear the chaos.

Just like Lightning McQueen: https://www.youtube.com/watch?v=AvhFjVj7k44

Not only are you less likely to crash -- you're less likely to cause a crash ten cars behind you.

This diagram changed how I think about following distance: https://entropicthoughts.com/keep-a-safe-following-distance

I find this diagram _incredibly_ hard to read. I’m pretty sure I understand the phenomenon he’s describing — without safe following distances, car n+1 must break more aggressively than car n in order to avoid a collision, so given a long enough chain of non-safe followers, a collision is guaranteed. But either I am dumber than I’d like, or that plot is terrible.

The plot is trying to illustrate the solution to an equation that is quite similar to Burger's equation, with a strong dependency on space and time. That's not easy to do in a single, static image.

When the characteristics meet (when the lines overlap), you get a shock wave. Or, in the current context, a traffic collision.

The choice of X and Y axis are absolutely terrible.

Thanks for sharing. I'm genuinely impressed to hear someone publicly share a story of growing self awareness and improvement.

On the other hand, at age 20, with very high premiums, I got one of these devices which never beeped except on a few too-short exit ramps on highways in my city. The choice on these exits is to slow down traffic on the highway, or endure a "hard stop" by braking immediately when you are on the ramp, and coming to a full stop at the stop sign.

Just a few of these was enough that my "discount" was only a few dollars. I regret giving Progressive my driving data.

I had a somewhat similar experience - as I recall, most beeps happened as a result of a few stop lights with too-short yellows (e.g. the light changes yellow and you, even though you are below the speed limit, either panic stop or run the red light)

The only possible fix as a driver was to try to develop an intuition for spotting “stale” greens and start slowing down despite the green, anticipating the yellow.

I feel at least partially vindicated by the fact the lights in question eventually had their yellows extended.

If there's no extra exit lane, the right choice is to slow down traffic on the highway.

What will happen if there's some oil spill or brake failure at the point you think you should break hard?

The exit ramp is not sufficiently short as to be unable to stop safely, even with my old 2001 Toyota Corolla. It is however sufficiently short that you cannot stop without recording a 'hard brake' on the Progressive Snapshot device.

Obviously the calculus changes at rush hour when the exit ramp (and highway) begin to back up. And in those cases, yes, of course the correct answer is to slow down before the ramp, even if it means impeding traffic. (Or take the next exit.)

Just for fun, there's also a very short entrance ramp onto a 65mph highway in this city, which requires you to accelerate uphill from a stop sign with a very limited runway (~200 ft.) This entrance has been responsible for far more accidents and crashes than the exit I initially described.

There is no upside to giving personal data to a for-profit company with a monolithic amount of money and a clear view of the statistics around any activity.

The incentives just don't line up.

I'm fine with having opted in to doing it for 30 days once.

Is there any vehicle that uses it's sensors to make a gentle suggestion about following distance?

It's probably the best single thing anyone can do to improve safety. It also reduces wear-and-tear on your car, and increases your fuel economy as a side benefit.

Why hasn't gamification of safe driving habits been built directly into the car itself before now?

My wife's VW will show the following distance and if you are too close a small icon is displayed on the dash. I believe its warning you that if there is emergency breaking required for the car it will not be able to stop in time.

It also shows how close you are to the car Infront in "car length" units with a nice big indicator and the adaptive cruse control will follow that distance mostly on its own between 30-100mph

Euro NCAP actually mandates that a following distance should be part of adaptive cruise control. A lot of manufacturers have turned this into a distance meter on the dash, in addition to the automatic braking. When I test-drove a Renault 5. I could see a little bar graph measuring how close I was to what the car thought was safe. Which turned out to be a lot closer than I would be comfortable driving! That is, the car would have allowed me to get much closer before it would have activated any automatic braking.

(the irony of looking at a meter on the dash to duplicate a piece of information I should be very clearly seeing out of the windscreen was not lost on me, though)

Automatic braking is a last resort to prevent serious injury to the occupants. That's not the same as safe following distance with adaptive cruise control. The closest my Tesla will go at 60 kph is about 15 m (three car lengths for my Model S) I think. I'm not sure because I normally keep it at maximum separation, about three seconds (50 m at 60 kph).

My Cupra Born does this; it has a little line that it draws on a "road" with the car in front, and you have to put the car in front of the line to be safe. Its quite a fun little system haha, works well on me!

A lot of them do. My wife's VW beeps an alert if you're too close to the car ahead of you. It might be that it only activates above a certain speed.

I think it will also back down the cruise control (if set) if it detects that you are gaining on the car ahead. That might be MILs Toyota though.

I learned the "two second rule" in Driver's Education 45 years ago and generally follow that. Nothing more annoying than having the car behind you riding your bumper.

My car beeps at me far too much now. I am responsible, not my car so I want less distractions.

Instead of pretending to shift responsibility to the car, how about people do training every so often instead? Maybe every ten years for an hour or two.

The amount of work a young person has to do here to be able to obtain a "full license" takes literal years and multiple tests.

But then nothing for the rest of their life despite advances in technology (in and out of the car) and changed traffic conditions...

One of the few things I really don't like about my Subbie is that it tries to help braking.

I'm all in for traction control and to some extent ABS, but braking hard and upsetting the car's balance when you don't need it is dangerous.

Is it one of those cars that alters the brake boost depending on circumstances?

That drives me nuts. When you put x amount of force into the brake pedal, you should know you're going to get y amount of deceleration. Don't double the brake boost just because you decided it's an emergency due to some opaque criteria.

I'm quite pleased to know that my Tesla S will assist me in braking when I stamp on the pedal. It's happened a couple of times and in both cases made sense and the car was under control all the time.

> Is it one of those cars that alters the brake boost depending on circumstances?

No, it's just breaking a bit too hard for you while the panel beeps and has scary red lights pop (that you'll have a hard time reading).

If you are referring to the alert stage of the emergency braking system, triggering it should be rare if you drive reasonably well. It is also most likely a situation in which you could benefit from a little more braking force.

If you decide to swerve, the additional weight at the front will help you to initiate the turn, and good systems will then reduce the braking force at the right moment to give you the most traction when cornering.

Yeah, most AEB systems I've used work quite well. I've had a couple false alarms (just at the warning stage) where I can at least understand why they happened from a system perspective, even if there was no risk.

I did find "normal" mode on the Model 3 was way too sensitive, but I set it to "late" and it's been fine ever since.

Pretty sure my EV9 will actually initiate emergency braking. Though it is pretty conservative (no nudge to follow at a safe distance).

> Why hasn't gamification of safe driving habits been built directly into the car itself before now?

I am so glad it hasn't. Data point of one, but gamification now has the opposite effect on me: it's such a well-worn pattern that it just annoys me. It was great when it was novel. I wonder how many others feel the same but without sampling it's hard to know.

I concur with you regarding gamification. When I am aware of the gamification it fills me with exhaustion to annoyance to extreme frustration. This is especially true of things that I want to use for one purpose.

I also think some of the car sensors (Subaru especially) that are trying to make you safer are notoriously bad.

I also find the random “coffee break” notice on Subarus frustrating.

My personal examples: “eyes on the road” - triggered frequently by one pair of sunglasses I have, looking left to check blind spot, checking mirrors, etc.

“Hands on the steering wheel” - triggered occasionally on long drives when I have been giving input, but very light input.

I drove one of our Kia Niro EVs that we have at work recently, and it started warning me to take a break about fifteen minutes into the drive.

I'd barely left the yard, certainly hadn't made it across town.

It went off when I actually did stop for a coffee, but went on again 15 minutes after I left the car park.

I have to say its various combinations of bings and bongs and beeps were about the most distracting thing I've ever experienced in a vehicle.

That’s pretty cool. Reminded me of reading [0] about how training surgeons using click feedback, like when you train a dog, works really well.

[0] https://www.npr.org/2018/06/12/619109741/clicker-training-fo...

I can only speak for Europe, but driving too closely to the driver in front is unfortunately how 90% of drivers drive.

Unless it’s in Netherlands, where it’s 100%.

I haven't been to the Netherlands, but I would say Paris is pretty close to 100%!

Kudos on you for acknowledging that your behavior changed! It is depressing how many people online are convinced that the emergency braking systems are too aggressive. The best is the cohort that insist these systems will be what causes accidents.

As a passenger, I really notice the difference, and I wish more drivers (including professionals) would learn as you did. It probably saves energy as well, especially when driving in cities, although I guess it's marginal.

Back when I had a Prius, I made a conscious effort to avoid using the brake pedal during the highway portion of my commute. It made a small difference to fuel economy, but treating it as a game reduced the frustration with stop&go traffic.

I don't think it's marginal since accelerating the car needs way more energy than fighting loses due to wind and tyre resistance.

Also, a bad driver mis-breaking trips the cars behind into breaking too, which multiplies the energy waste and may also cause accidents through fatigue.

Mare experienced drivers will give you more leeway to avoid tapping the brakes with you, or simply go for a staring overtake.

People here in Tokyo follow at obscenely tight distance on the freeways and motorways. Drives me crazy. Don't have the data, but having driven here for over 20 years, I’d venture that short following distances must be one of the main causes of accidents on these types of roads. People are otherwise generally cautious and attentive drivers. When I’ve expressed frustration about it to locals in the past, the response is often “but if you leave more space, people will cut in!” To which I respond, “okay, and?!” I feel like a single big media campaign to improve following distances could result in a big improvement. So frustrating.

>I'd follow the drivers in front of me too closely

Best trick for managing this is to "drive through" the car in front of you. That is, judge your following distance based not on the car in front of you, but on the car in front of THEM.

And you don't have to "drive through" all the way down the road - it only takes one car/one level of abstraction for this approach to yield really great benefits, try it if you don't believe me.

This only works if you can see two vehicles ahead. Too many SUVs and pickup trucks are too high and have terrible visibility around them.

I have a friend who would also follow too closely to the cars in front and got one of these. Her rates went up and she eventually got into an accident (no injuries to anyone) because she would follow too closely and still break too hard.

Now she still has the machine, still follows too closely, and still breaks too hard in her new car...

Good it worked for you though!

A cousin of mine is abysmal to drive with as a passenger. He follows too closely to the car in front of him, regardless of lane / speed. He will slow down, follow closely, and then aggressively pass. Repeating ad nauseam.

No smooth maintaining of speed and nice passes as able without slowing down.

Surprisingly, his accidents have mostly seemed to involve gas pumps, barriers, and other obstacles at low speed.

I believe inattentive driving correlates more with accidents than things like hard braking, and might be the leading cause of hard braking too (inattentive driving will lead to following distance being reduced too as you are not watching for traffic well ahead and to the side of you).

At the same time, passing on regular intercity road can have the risk reduced (up to a point) by making the passing quicker, by spending less time in the oncoming traffic lane ("aggressive passing"). It certainly does not help with comfort, though.

So perhaps your cousin is a very attentive driver who drives aggressively? That might still only make him an "average" driver (I've had such drivers almost get others in an accident in front of me), but I think it's a balance that needs to be struck, otherwise most would tune out and not be ready for emergencies.

This is left lane driving policy. I am like this, and I was not at first. What makes you drive like this is rush hour traffic. "Move up the lane or move out of the lane" is the sentiment, basically. As others have noted, it is essentially an adversarial process. If you drive nice, people cut in front and you're unable to drive nice to both those behind you and in front.

I don’t think what you’re describing is quite the same thing.

At least I hope not.

More concrete example:

He will be going 65 mph in slow lane. Come up on a car. (Left lane empty). Slam on his brakes. Follow them at 50 mph for 1-3 minutes <1 car length.

Pass, flooring it, if he stays in the left lane he’ll keep going until he now tail gates a car in front of him- usually with large speed variances.

The amount of traffic on the road doesn’t matter. It can be 3 cars and he will drive this way.

I’m not talking about trying to drive through major city rush hour traffic.

Letting them "cut in front" is good driving.

If you have to keep significantly slowing down to get the gap back, that's perfectly nice to the people in front of you but it's not nice to the people behind you.

Inter-car distance is always a safety factor but can immensely reduce lane throughput. There is a compromise. I remember a few decades ago, in California at least, they suggested the drivers keep a one-car length distance from the leading car for every 10m/h speed. Funny that I had to convert it in km/h.

Inter car distance is highly irrelevant as the overall speed will quickly drop due to excessive braking due to tailgating. Maximum throughout is around 60kph. You keep 2s distance if you want to be safe. So at highway speeds that is around 50 to 70 meters

not dying >>>>>> lane throughput

I am sure this rule of thumb was suggested after thoughtful weighing of traffic accident risk and jams in Cali's 8-lane highways. Everything is a compromise, often versus life.

I'm always surprised at the number of people that follow too closely.

This always stuck with me

https://www.youtube.com/watch?v=iJFOTSYJrtw&t=466s

I have this image in my mind of a discussion taking place in a high speed rail possibly around 2100 where people will look back and say: "I cannot believe we had people driving 2ton steel boxes back in the day, I cannot even compute those micromorts"

I was recently driving a friend and hit a mile-long backup at a freeway exit. At some point in the lineup, a car abruptly cut in front of me to merge into the line. The friend asked "why'd you let them in" - but I didn't let them in on purpose, I was just maintaining a reasonable following distance which people seem to interpret as "hey cut in here for free"

The balance between safe following distance and letting people cut in varies a lot by city. Maybe he learnt to drive elsewhere?

I remember being too aggressive when I got to the Bay Area, and learning how nice it was to be let into the lane I needed to avoid being forced on a 5mi U-turn. When visiting back home I was too nice and people told me so.

I've reached a balance. Aggressive enough not to be taken advantage of, but being nice to drivers in need, specially when it doesn't really change things for me, like when letting a driver in costs me nothing because of how bad traffic is.

It is called the zipper merge. You were in the wrong for waiting in the stophed lane and the other person right for passing all you thinking you are better.

I'm pretty sure the other person is not talking about a 2-to-1 lane merge.

Calling that person an idiot for your misunderstanding is not cool.

It would be really interesting if cars did this by default. Maybe it could figure out your threshold, how much of an outlier you are, and then you could opt-in to a new threshold that's somewhat better and/or closer to average.

As one of my friends put it - driving in the US is like being in Whacky Races.

If you have to brake hard, it is still important to not brake harder than necessary, to give the cars behind you the best possible chance to react in time.

While i find everything about this post thoroughly dystopian; I will state that I don't break harshly, just about ever, my car still has it's original breakpads (they still have some life, about a cm and a half to two) and it had 107k on the odo. Never been in an accident outside of getting break-checked by an insurance scammer when I was 19, and a head on when i was stopped at a stop sign.

Although I keep a varying follow distance, if there is an open lane immediately adjacent to me, I don't care if i'm tailing someone a bit, but if I'm boxed then you better believe it's 6+ car distance.

I've long thought that drivers should have some kind of black box monitoring their driving habits/abilities with that kind of acceleration sensing. As well as feeding into insurance databases to give safer drivers lower premiums, I think it would be ideal to highlight when older drivers start to lose their faculties. Another big benefit could be to diagnose some diseases early on - if a driver suddenly becomes less smooth, there's a good chance that they have some new eye or brain condition.

> It was a lack of appropriate following distance.

Not in my case. I keep plenty of following distance, 9 times out of 10 my hard braking is because some idiot cuts into that following distance and brake-checks me.

Driving predictably and smoothly is good. The only time there should be any braking considered remotely "hard" would be when something surprised you, which should almost never happen.

Insurance erotica right here lol

The problem with increasing your following distance though is now you get other drivers cutting in, and you’re back to where you started

> you’re back to where you started

This perfectly illustrates this broken mental model that leads to endless frustration.

Unless you put the car in reverse, you are still making forward progress. If someone merges in front of you at 30mph then you traveled hundreds of feet towards your destination in the time it took them to do that. Chill out.

Only two, then people who maintain their lane are there and there is space.

This type of research is highly valuable but too rare; this is generally because of how we view Road Accidents at a core level:

- Road Accidents: "A driver caused this, let's determine who, and find them at fault."

- With Air Accidents: "The system caused this, let's determine which elements came together that ultimately lead to this event."

The first is essentially simplifying a complex series of events into something black and white. Easy to digest. We'll then keep doing it over and over again because we never changed the circumstances.

The second approach is holistic, for example even if the pilot made a mistake, why did they make a mistake, and what can we do to prevent that mistake (e.g. training, culture, etc)? But maybe other elements also played a part like mechanical, software, airport lightning, communications, etc.

I bet everyone reading this knows of a road near them that is an accident hotspot and I bet they can explain WHY it is. I certainly do/can, and I see cops with crashed cars there on a weekly basis. Zero changes have been made to the conditions.

Because for air travel we pre filter out the morons who are drunk, untrained, scrolling facebook, etc. Any incident left is overwhelmingly more likely a systems issue. For a road incident, the most likely cause was just one driver was violating one or more rules. The only system failure was not canceling their license beforehand.

While that is true, "Drivers consistently ignoring rules" is also a systems issue, which can be mitigated through e.g. better road design (narrower roads reduce speeding, for example).

Or “design cities to be less car centric so we can keep the antisocial drivers out of a car”. It's definitely a system issue.

Why jump to cities? Low speed traffic in cities is not the main location of car collisions.

The main issue is highways and rural roads.

    The main issue is highways and rural roads.

It seems we are talking about different things.

The majority of car collisions happen on urban roads where the majority of cars are.

The majority of fatal collisions occur on rural roads, where vehicles are travelling faster.

I live in the UK.

https://www.simplyquote.co.uk/insights/where-do-most-car-acc...

“Highways” and “city” aren't incompatible, quite the opposite: most of the traffic on highways is commuting, in urban areas.

.... in the USA.

I live in the UK where highways majority used for inter city transport.

I can't tell about the UK, but it's definitely true as well in France and Germany.

And a quick look at map of London and Birmingham suggests that it may very well be the case in the UK as well…

Maybe actually looking at research and statistics might serve you better than casually glancing at maps and taking wild guesses.

I'll get you started:

https://www.gov.uk/government/statistics/national-travel-sur...

> The only system failure was not canceling their license beforehand.

Why was their license not canceled beforehand?

Did they not get caught? If so, why? Likely other drivers have noticed the bad driving behavior. If so, why did they not report it? If they did report it, did the reports get ignored? Is there even a system and process in place for such reporting?

If they got caught, was there hesitation to revoke their license? If so, why? A potential factor would be driving in an area where you have to drive to get anywhere, which is common in the US. Why has it not been addressed that you have to drive, even if your driving habits are bad?

If bad driving behavior is too hard to punish, why? If regulations do not allow adequate punishment of bad driving behavior, why have these regulations not been changed? If evidence is missing, what evidence would that be, and how could it be collected?

If the driver was drunk, what would have been the alternative to driving? Is there adequate public transportation for drunks to get home? "adequate" depends on the drinking culture in the area where that happened.

If the driver was untrained, why were they allowed to drive? You wrote about canceling their license, so they did get a license. How was that possible without training? Does the process for handing out licenses have to be changed? Is frequent re-training necessary (more data is needed for that; if that data isn't avilable, why not?)

Obligatory link to the CAST handbook in case you want to follow that line of thinking: http://sunnyday.mit.edu/CAST-Handbook.pdf

> This type of research is highly valuable but too rare; this is generally because of how we view Road Accidents at a core level:

"Crash" not "accident":

* https://crashnotaccident.com

An issue of volume, I would guess. If my quickly gathered stats are accurate, there are on the order of 100K commercial flights every day, and 1B drives. So road accidents are expected to be more numerous, and they usually have less impact than an airliner going down. Also - the NTSB does indeed investigate car accidents on occasion, and when they do, they definitely include systemic analysis.

much easier too investigate and solve though. a few lines of paint here, a bollard there.

Aim to make the road laminar. Every time you hard brake, you're causing the milk jug to glug, making a ripple of entropy as momentum turns to heat from your brakes and those behind you, sometimes in perpetuity. I learned this while doing a 1.5hr daily commute in a Subaru with a clapped out manual transmission. I wanted to conserve energy shifting, but realized I was now participating in large choreographed dance of "smooth" with other drivers who already knew this. There are many of us. And we all glare at the driver blinking their red lights on the interstate indicating that they're loud and proud of introducing turbulence to an otherwise peaceful system.

I try to do the same, and do my part to smooth out the wrinkles in traffic.

What I would really like in a car is not only my current speed, but the relative speed to the car ahead of me. Given my car has cameras and other sensors for cruise control and other features this ought to already be possible.

https://www.youtube.com/watch?v=Suugn-p5C1M

This is the natural response of tapping the brakes for any slowdown: people naturally over compensating and chain reactions happening behind them. This video shows how stop and go traffic forms and snowballs with no real impetus beyond mis estimated follow distance.

IMO there is nothing worse than drivers on highways who think that by leaving bigger gaps and slowing less rapidly they are 'smoothing' out the traffic and helping the whole road run better. You are not, you are just making the whole road run slower and taking up more space for yourself on a crowded road.

This is untrue, there have been studies done that discovered the primary cause of traffic is following too close. Following further away really does reduce the amount of traffic. It seems unintuitive, but consider: every time you brake, the person behind you has to brake a teensy bit longer. And then the person behind them, and behind them. That little bit of extra time accumulated quickly and grinds the highway to a halt.

I think there's nothing worse than drivers who feel entitled to go fast at the expense of everyone else's safety.

Yeah, I agree fully with you on that point.

However purposely making the cars behind you break more and causing more compression further back just so that you can avoid the compression in front of you is madness.

Of course braking/change in velocity creates waves. But this effect is overemphasized in my opinion. Locally analyzed, traffic can be simplified incredibly by observing that a lane's maximum throughput is simply given by following spacing, measured in time.

If drivers are using a 2 second following distance, commonly taught in driving school, then max throughput is simply

  1 car / 2 sec

This assumes that a 2 second interval is appropriate for all travelling speeds.

This assumption is untrue at very low speeds, particularly when it takes longer than 2 seconds for a car to pass a point. For instance if we assume cars are 4m long, then with an interval of 2 seconds the cars would be touching at 4.47mph

The assumption is also untrue at very high speeds. You'll want a larger gap. That's partly because at such high speeds the ability of a vehicle to decelerate differs - if a vehicle with good brakes does an emergency stop and the car behind it has a respectable 2 second gap but has worse brakes then they can end up colliding. It's also partly because a 2 second gap at very high speeds means the car in front is further away, and that can cause a greater delay before the driver realises what is happening. As a third reason a greater margin needs to be used at very high speeds simply because the consequences of a crash are that much greater and should therefore be avoided even more than at lower speeds.

Therefore there is a kind of U-shaped curve in the "safe" following interval, and consequently a speed at which safe throughput is maximised.

That's why variable speed limits have been introduced in various places. For instance, in the UK which normally has a 70mph speed limit on motorways, in very high traffic conditions this can be lowered using electronic signs to increase the safe throughput of the road. It's commonly reduced to 50mph, though it does get lowered further in sections approaching a queue of vehicles that has actually stopped.

There's also the issue of speed oscillations. With a high speed limit and vehicles following too closely, a little variation in speed in one vehicle can turn into a larger variation in the following vehicles, causing a backwards-travelling wave of braking (sometimes to an absolute halt) and speeding up again. Lowering the speed limit reduces this.

By 2 sec following distance I am referring to their back bumper to your front bumper. So cars "overlapping" in your example is not possible

If you want 4 sec gap at higher speeds that's fine, the formula is speed-independent for throughput, not speed-independent for following distance. If you want 4 seconds at high speed then use 4 sec instead of 2 sec (i.e. 1 car/ 4 sec)

>There's also the issue of speed oscillations. With a high speed limit and vehicles following too closely, a little variation in speed in one vehicle can turn into a larger variation in the following vehicles, causing a backwards-travelling wave of braking (sometimes to an absolute halt) and speeding up again. Lowering the speed limit reduces this.

"Lowering the speed limit reduces oscillations." Exactly, that is my whole point, that (again, locally analyzed) you can ignore the waves, and instead look only at the following distance of the slowest car in the lane, to determine throughput of the road behind that car. Your idea of "lowering the speed limit" to eliminate waves is the same net effect on throughput as observing that the throughput cannot exceed that given by the longest-following car on the road.

A niggle - if you are referring to a 2 second gap between the back bumper and the following front bumper, then the formula is no longer speed independent, as you need to add the small overhead to account for the time taken for the length of the vehicle to pass as well. This will be small enough to be mostly negligible except at low speeds.

Totally.

If you take this measurement as the goal it would be best at near standstill speed (around 4m/s). If you want to maximize the traveled distance of the group it is around 60kph, which is the metric most people actually care about when discussing throughput.

1 car / (actual max following time) no matter the speed. Where do you see speed in the equation? It's not. You can put it in of course but my point is it's unnecessary if you know following distance, which is theoretically more invariable than speed on a road anyway

> If you double following distance, you halve the throughput. If you halve following distance, you double your throughput.

That postulate breaks down as soon as you move away from a laminar traffic assumption and include distracted drivers, lane changes, and weather influences. Which is why the wave theory model is important to understand the propagation of perturbations and their effect on maximum throughput.

> The throughput of a (full, i.e. rush-hour) road has nothing to do with speeds of people driving, and everything to do with following distance.

And yet, in the limit case of a bumper-to-bumper situation (or, in fluid dynamics parlance, an incompressible flow), the variable determining the change in mass flow-rate is the velocity of the medium. Mimetically, we could also look at ants. To ease congestion in a bumper-to-bumper situation, they accelerate.

YES to all! You're so close. Drivers do not accelerate in bumper-to-bumper the way ants do. They maintain a 2sec (or whatever they are trained) following time instead. Which therefore dictates velocity (car lengths per following time). Thus the limiter on flow-rate is actually following time!

THIS this so much. Look far out ahead and if you see traffic compressing then slow down sooner so as to try to make that compression vanish for those behind you.

The tradeoff for the compression 'vanishing' is longer times pressing your breaks, travelling slower overall, and leaving your engine running for more of the time.

Also you then just leave a bigger gap in front of you for somebody to jump into, forcing you to break more and go further back to maintain your distance. This in turn just winds up the drivers behind you who end up overtaking you. All this chaos becasue you think you are helping by 'reducing compression'.

In heavy traffic I much prefer to quickly catch the car in front up and then sit stationary with my engine off. Much more efficient and less polluting than spending the whole time with your ewngine on managing gaps and braking distances at low speeds.

Lube the road.

Nice research. This is fairly well known in insurance circles. Most auto insurers that do telematics consider hard braking the strongest indicator of risk. One of the things that we do at work (Cambridge Mobile Telematics) is build tools to deal with this risk. We have apps that monitor driving and we play a tone to indicate that a hard braking event was detected. Simply letting people know that they had a hard braking event is an effective mechanism for behavior change (other companies have similar tech)

Insurance is thinking about hard braking as an indicator of a driver with riskier behaviour. Google is showing that it can also be an indicator of risky road designs. These actually kind of point in opposite directions in terms of the causes of hard braking. The certainly can be used in different ways.

They point in opposite directions because they’re not measuring the same things.

Google is measuring where on the road most hard braking events happen.

Insurers measure who is having the most hard braking events.

Problem with insurance companies measuring risk this way is that local government externalises costs of bad road design to the people who are unfortunate to have to drive there.

Makes you wonder why there aren't more insurance companies out there using their data to lobby local governments to fix their road design. They have all the data to find hotspots, and reducing accidents would increase their margin.

Maybe this would require an insurance company to have outsized market share in a specific area so they are the main beneficiary of the improvement

It should also be generalize to when (for example a specific corner during dusk or dawn), and for insurers what would also be an important factor would be what other cars are nearby at the hard-braking event, it's not exactly productive to flag the chicken in chicken-or-dare scenario's.

(Though for an insurer, it’s the same thing - whether you’re risky because you’re a bad driver or because you drive on poorly constructed roads or around other poor drivers is inconsequential to them)

Yeah well fuck insurers. We are supposed to get spied upon by our cars with their blackboxes, by our insurers, by Google, by national security services of various countries... and what do we get in return? Dinged for other people's bad behavior which we cannot reasonably control. Either you follow the car in front of you very closely and get hard braking events, or other people switch lanes in front of you and in the worst case slowing down during lane change, provoking yet another hard braking event.

Fuck all of that.

Credit scores are universally hated but they make it possible to offer lower interest rates to more people. Without credit scores, fewer people would have access to credit.

Similarly, people often don't like it when insurers track and score their driving. However, this allows insurers to offer lower insurance fees to more people by _not_ offering lower insurance fees (or instead charging higher fees) to people that are driving in a risky manner. This does of course assume a competitive market for insurance but I think in most countries that's a reasonable assumption.

There's nothing fairer than user-pays, especially when users can choose to pay less by changing their behavior.

> Credit scores are universally hated but they make it possible to offer lower interest rates to more people.

That's probably true in theory, but not in practice, given how high US credit interest rates are compared to European countries for instance.

> Without credit scores, fewer people would have access to credit.

Too many people having access to credit is exactly how we got the worst financial crisis of the century, so it's not really something to brag about… People talk about US public debt a lot, but private debt is even more worrisome.

>There's nothing fairer than user-pays, especially when users can choose to pay less by changing their behavior.

If user pays is so fair why does anyone who could access credit or liquid assets in excess of their state's minimums have to pay hundreds to thousands per year for auto insurance?

Most states allow you to go without insurance by fronting the cash. It's called self-insurance. You put up some minimum amount, file a form with the state DMV, and keep the approval certificate in the vehicle like normal.

It's relatively unknown for individuals because most people have no desire to lock up tens or hundreds of thousands of spare dollars just to avoid car insurance. As far as I'm aware it's primarily used by rich collectors who need to insure large collections that don't fit more traditional insurance profiles. Much more useful for businesses.

>Most states allow you to go without insurance by fronting the cash.

That's BS on it's face. Most states don't allow it or they restrict it to big business and government agencies.

>because most people have no desire to lock up tens or hundreds of thousands of spare dollars just to avoid car insurance.

Most people's money isn't making a return greater than what insurance would cost them.

Second, this completely ignores my point about credit. I can easily get hundreds of thousands of dollars in credit secured against my house or tens of thousands in unsecured credit (credit card). Why must I pay to keep the lights on at some insurance firm?

And I'm not particularly rich. If the numbers pencil out for me then surely they must pencil out for millions of people.

    That's BS on it's face. Most states don't allow it or they restrict it to big business and government agencies.

    Most people's money isn't making a return greater than what insurance would cost them.

    Second, this completely ignores my point about credit.

States' interest here is in guaranteeing that there will always be a minimum amount of money to compensate victims, regardless of what other financial shenanigans you have going on in your life. That's not a standard that lines of credit and investment accounts meet. Self-insurance is simply a terrible option for most consumers, so no one does it.

That's an entirely separate issue, isn't it? In my country (New Zealand) there are no requirements to have auto insurance. If you don't have insurance and you hit a million-dollar car you're gonna be in an awkward situation, but that's a risk you're allowed to take.

Note that you _are_ legally required to pay your annual ACC levies, which fund no-fault cover for injuries. However that doesn't cover property damage.

So, what's your proposal? What should insurers be doing differently?

Operate like they did before they had access to surveillance technology that would have made Gestapo and Stasi blush

This. If you're nearly "perfectly" pricing risk on an individual level then you defeat the point of insurance which is to pool risk.

If my hypothetical cost over an N decade period is within a fraction of a percent of payouts in that time what do I gain by paying for insurance other than creating a principal-agent problem?

You’re mad the insurance companies are charging you what you owe? You do have the option to self-insure.

Some road designs are risky because they encourage risky behavior. And "risky" is relative. A good driver should recognize risky road segments and drive even more defensively than normally.

This is true - but it’s hard even for “good” drivers to always understand especially on roads they might not be familiar with.

Example: open space on either side of the road, tends to encourage people to drive faster.

Closing that space (whether by buildings, shrubbery, etc ) will slow the speed.

But I will say there are also “obvious” bad designs - the rare far to short on ramp to merge, where drivers don’t understand how to adjust.

Or the one I most frequently encounter are “blind spots” created by the speed of an intersecting road, where a mirror may be attached to a pole / tree, or a sign reminding people to look left right left, or even instructing where cars should be beyond for a safe pull out.

I know of one intersection near me that both has markers on the road(don’t pull out if cars are at or beyond this marker), and a reminder about looking, but still has a high frequency of accidents.

There's some that are purely due to space constraints, favourite pet-peeve example is a highway with an overpass crossing it.

In the rural case, the offramp will branch off first and the on ramp will be after the overpass and the drivers taking each never meet.

In the space constrained case, theres one extra lane that serves both, where the drivers taking the on-ramp cross paths with those taking the off ramp. This configuration is absolutely cursed!

A driver who frequents risky roads is a concern to insurers, just as a driver who has risky behaviors.

The cause of hard braking isn’t mutually exclusive: bad driving or bad road design.

Similarly, a road that is frequently travelled by risky drivers is a risky road!

This is part of the reason insurers include zip code in their risk profiles.

Driving on bad roads is just as bad for insurance as a bad driver is.

My mom had a device installed in her car to get a discount on her insurance, and she was always upset at the hard braking thing - whenever she did it, it was because another car was doing something unsafe that she couldn't control, like pulling out in front of her.

Some amount of that is inevitable, but there is another level of defensive driving where you anticipate poor behavior and arrange that it won't cause an accident.

Have a look at a few dash cam accident videos [1]. There are many maladaptive patterns of behavior, but a frequent one that the average good driver can improve on is limiting speed on two occasions: when approaching a blind spot, and when passing stopped or slow traffic.

That second one gets lots of otherwise good drivers. They seem to think that by limiting their speed vs slow/stopped traffic they'd be encouraging people to dart in front of them. Which is somewhat true. But with limited speed, that's an avoidable or less injurious accident. By gunning it past stopped traffic, you make the accident unavoidable and more serious.

[1] https://www.youtube.com/@IdiotsInCars1

Without wanting to paint with too broad a brush, I would say in my experience driving in 10x countries, U.S. drivers, being most habituated to spending their lives in cars, drive in the most distracted, least careful way. Especially in places where the typology is the U.S. default of low-density, car-oriented sprawl. Accordingly there are an appaling number of deaths and injuries on the road: 1 in 43,750 people dies each year in the U.K. in automobile accidents vs. 1 in 8,500 in the U.S.A.

Inb4 deaths per mile driven, I'd argue higher VMT in the U.S.A. only proves the point - too many cars being driven too much because of silly land use. High VMT is acutally a symptom of a dangerous mobility system as much as a cause.

Add to that the relative ease to get a license in the US, and the level of punishment for breaking the laws.

I (an American) was on holiday and Switzerland and was explained the process of getting your license back if you lose it. It is a big disincentive to driving badly and putting yourself at risk of that, to be sure.

Coming from outside the US, I was shocked to see how many drivers were on their phones _while the car is in motion_, scrolling Instagram or similar.

Adding on to this, a common reaction I see to online videos of driving incidents is "why did this person just stop? of course you are going to crash into them. They shouldn't have stopped" and many people agreeing with it. It seems they are blind to the fact that if the following driver was using a safe following distance and speed, they should easily be able to stop, making the incident the fault of the driver following too close, not the one stopping.

I haven't checked on this in a long time, but IIRC, the insurance company will always blame the person in back in a rear-end collision, for just this reason. A rear-end collision should always be avoidable.

Usually but not always. A common insurance scam is to pass a car, cut in just in front of it, then brake hard causing a collision. Dash cams video is a good thing to have to fight this if it happens to you.

No, even then. If a car cuts in front of you, you have at least a few seconds of time to start making space for them, and once they are in front of you, you should immediately make a safe amount of space between you and them.

Yes, in a country where safe driving is not internalized you will inevitable have someone rear-ending you while doing this, but if the options are "accident where you're at fault" and "accident where you're not at fault", pick the latter.

I think you’re misunderstanding, the person pulling in front is not giving you seconds to make space - they are deliberately trying to crash into you.

Some degree of road safety depends on predictable behavior. I haven’t seen those videos, but suddenly executing a panic stop on the freeway for no good reason at all increases everyone’s risk, even if the car behind you is following at a safe distance. Obviously the following driver bears the most responsibility, but erratic drivers shouldn’t be held to be morally blameless.

> erratic drivers

People don’t usually act erratically for no reason. Maybe they suddenly stop because they see a deer sprinting towards the road off in the distance, and the person behind them didn’t see it. There are tons of reasons that look like they “erratically stop”, which are actually genuine safe behavior that the other may not know about.

People act erratically all of the time on the road because they're on their phones while driving instead of paying attention.

People also don’t realize that just because you can does not mean the insurance will side with you 100%.

I learned next-level defensive driving by bicycle commuting to work 5.5 miles each way on busy roads in rush hour traffic. On a bicycle you're invisible, and if you expect any less, you're going to get hurt. As it was, I had some very very close calls- at least one of them had the potential to be fatal. Ironically, the only time I ever crashed was my own fault.

But now even when in a car, I retain that "I'm invisible" mentality, which makes me much more aware of what other drivers are doing, and much more skeptical of their ability to make good decisions. This has saved me several times.

>I learned next-level defensive driving by bicycle commuting to work 5.5 miles each way on busy roads in rush hour traffic

please stop doing that geocrasher

The landing page video's first incident is a car coming from behind and from the right, cutting off the filming car. The filming car didn't react at all when instant (but measured) braking would've been safer to start building a distance buffer.

One thing HPDE taught me is that most people under brake in dangerous situations because they simply don't know the limit of their vehicle nor the sensitivity range of the brake pedal.

The hard braking heuristic makes sense when estimating risk of road segments, but not as a proxy for driver competence.

It certainly makes sense as a proxy for competence across a diverse population for insurance purposes. You have a baseline of hard braking events that a competent driver may encounter under normal circumstances. If a driver routinely exceeds that number, they are either unable to correctly estimate closing distance and reaction times, which makes them higher risk for causing accidents, or they are driving abnormally aggressively, which also makes them a higher risk for causing accidents. If you consistently put yourself in situations where hard braking is required, it doesn't matter what your skill is, you've reduced your safety margins and an accident is statistically more probable. You said it correctly with "would've been safer to start building a distance buffer", that is the proxy the insurance companies want to use for risk assessment.

35 years without an accident on my record isn't because I'm a magnificent driver, it's because I always try to leave a way out for when something unexpected happens, because the unexpected _does_ happen.

The fact that some people may have the skill to drive more aggressively means nothing in the aggregate as far as insurance companies are concerned. If you are skilled enough to drive in that manner, you are skilled enough to avoid it as well. It's simply statistics.

> You said it correctly with "would've been safer to start building a distance buffer", that is the proxy the insurance companies want to use for risk assessment.

Then use it? Mandate reaction speed tests or other driving mechanics competency evaluation (not road sign comprehension) and watch insurance margins explode.

The driver in my example did poorly and scored top marks in the heuristic.

I assume you are referring to this video: https://www.youtube.com/watch?v=sEpHyMtDcPY

> building a distance buffer", that is the proxy the insurance companies want to use for risk assessment.

The cam car did not need to have a hard braking event (HBE) to start building distance.

Even if they did, the insurance companies are looking for a pattern of HBEs to assess risk. I agree that there is a theoretical high-risk driver that never has a HBE because they always try to maneuver instead of breaking. There are other heuristics for this (high lateral acceleration, high jerk). And the ultimate heuristic: failing to avoid accidents, thus having a claim history.

> One thing HPDE taught me is that most people under brake in dangerous situations because they simply don't know the limit of their vehicle nor the sensitivity range of the brake pedal.

On any modern car, just push it all the way and let ABS and stability control figure it out, and don't let the vibrating brake pedal spook you into releasing it. That's just ABS doing its thing.

Really though, getting a license is too easy in the USA. We really need to require some sort of car control course, including obstacle avoidance in the rain. Would be really nice too if it included an obstacle avoidance course in two cars: A huge SUV or pick-up truck and a more reasonably sized sedan. So many drivers think they need a huge vehicle to be safe while being completely unaware of how well smaller cars can likely avoid the crashes to begin with. Would probably get really expensive really quickly, though.

One thing I noticed among dash cam videos is very often the person recording and publishing the video will keep on driving closely behind another car that is clearly driving erratically. Maybe he will honk, but he won't brake or leave any safety distance, and seconds later the idiot's car, which has been behaving weirdly in front of him the whole time, causes him to crash.

I realize this may come off as victim blaming, but I feel you should have an obligation to not endanger yourself even if by the laws of the road you are technically in the right. I would rather get cut off by and idiot and be at my destination thirty seconds later than having to deal with car repairs even when it is legally speaking not my fault.

If you take a seasoned motorcycle rider and put them in one of those dashcam subs, they'll rip their hair out.

Most people have near zero defensive driving skill, and view someone pulling out in front of them as "nothing I could have done", when the dashcam shows the offending driver showed 5 signs of pulling out ages before the accident occurred.

At one point in my life I rode a bicycle 40+ km per day. I see things nobody else seems to and I think that has a lot to do with it. I cannot win the collision.

Much of being a good driver is just awareness.

One time my light turns green, I don't go. As my wife asks what I'm waiting for, a pickup blows the light. We weren't the first car at that light, and years later she still talks about how there's no way I could know. Well, I didn't get us t-boned at 80 so I must have done something right.

Very true. There is a "body language" to driving. I can often predict when someone will change lanes before they ever turn their signal on (if they even do that) by the way their speed changes and they drift a bit in their lane as they shift their eyes to their mirrors.

Cyclists too.

I do both and I am constantly surprised at the lack of situational awareness of drivers when I’m a passenger in their cars.

I think truckers probably get the same thing too.

Same, I cycle everywhere and almost feels like I've developed a sixth sense for when a driver will do something stupid.

I'm definitely a better driver because of bicycling. You gain new skills when you know that you're going to come out the loser in almost every collision.

If you cycle and it doesn't make you a better driver (and pedestrian) you're probably a bad driver and a bad cyclist.

A seasoned motorcycle rider should be unable to rip out any hair, due to safely wearing a helmet!

A helmet is priority #100. If your helmet ever comes into play, you've fucked up so bad it'll probably not help you much.

Drivers often believe that their insurance rates should be based solely on whether they follow driving rules, but the risks to insurance are not isolated to this. Someone can follow every rule perfectly, but if they are involved in an accident they incur costs for their insurance company.

If they are not found at fault then indeed there's no cost for their insurance company?

A common misconception.

First, the insurance company incurs costs just processing the claim. If things escalate with the other party, they may even incur legal and court costs.

Additionally, there are some costs that are incurred regardless of fault -- like personal injury protection.

Even defining "who was at fault" is a complicated situation. A lot of people presume that it is as simple as: whoever the police issues a citation to at the scene is 100% at fault. But that's not the way things actually work. The way liability is assigned depends on the state, but in a comparative negligence state you could be proportionately liable for as little as one percent of the fault of the accident. Maybe someone else ran a red light, you entered the intersection on green, and hit them. You could end up sharing some of the cost for that, if it is found that you could have avoided the accident but decided not to.

And even after all of this, if the other party runs out of money, doesn't have insurance, or runs away at the scene, your insurance company is stuck paying the costs under their uninsured/underinsurred motorist coverage.

There might be, if the at-fault driver is uninsured and you are carrying uninsured motorist coverage.

It does cost them just to process the claim because the other guys side is unlikely to completely roll over if there is any chance to reduce the payout. Obviously its not as much as the claims themselves but it also isn't free.

Yep. I have a friend that was plowed into from behind while waiting at a red light, twice within a few months time. Two separate intersections. Totaled her car both times. Her insurance rates went up, even though she was clearly not at fault.

"Not at fault" as far as the law is concerned, is a low bar. If you're one of the last cars in a queue, you should be checking your mirrors for exactly this scenario. Throwing your hands up in the air saying "well the law says I did no wrong!" isn't the way. Unless you like getting into accidents.

Also, having two of the same type of accident twice in such a short time is so improbable, that I'm seriously doubting your friend. I'd say it's way more likely she braked too suddenly or has other bad driving habits that make such accidents more likely than that she got this unlucky.

I hate the warning myself and I use the app the parent is from. I also suspect I am an outlier in not having an accident in 20 years.

It’s this obnoxious audio warning that tells me I had a hard breaking and it’s 9/10 because I stopped at a red light that I would not have made on yellow. And then it sends me tips and reminders about reducing hard breaking events and it’s annoying. I know they have done the analysis but it detects moderate hard breaking which is frustrating. One of those things that I am sure in net is positive but perhaps slices of the population it does not benefit.

The lights should be timed so that you don't have to do that if you are driving the posted speed, but I know that's not always true.

No doubt but I think it’s two fold. Lights stink in that so many are setup not for safety so they rip through the yellow quick as possible. Second, I don’t think of these as hard breaking even but I am sure from a data perspective the cutoff is probably correct. Hard invokes a vision of an emergency brake event. These apps really capture any medium to hard brake event.

It is not possible to time lights that way over any significant distance in a multi-way fabric of traffic.

> Simply letting people know that they had a hard braking event is an effective mechanism for behavior change

Has this been studied in isolation? Many of the tools that notify upon hard braking also are used to impose financial penalties for doing so... I suspect people may be reacting to the financial incentives.

Yep. We work with CMT and we’ve both done extensive testing on this. I think that often people don’t necessarily know what a hard braking event actually means, or how it’s quantified. Giving that realtime feedback helps close that gap in understanding

When people learn to do things by reacting to inputs, they learn much better when the input comes soon after the action/inaction they are trying to train, rather than long after. When you can tie specific acts as a driver to a later financial penalty it helps you learn to avoid the specific acts, otherwise you'd stuck having to figure out in three weeks when the bill comes around what you were doing on the date the insurance statement flagged as a hard stop.

Anecdotally: I leave the fuel efficiency display as the instrument cluster display on the hybrid that I drive and it significantly changes both my acceleration and braking behavior.

There is a minor financial aspect (price of fuel), but I’m far more interested in seeing if I can get a better “green score” at the end of the drive.

Does it matter why? The important part is getting people to change behavior.

of course if they change such that they don't break hard when needed that is bad, but if the change such that they don't need to break hard in the first place because they slow down in places that are dangerious that is the point.

> Does it matter why? The important part is getting people to change behavior.

Yeah, if you want to do that, it would be helpful to know whether a financial incentive is required for the effect or not.

When you modify their braking behavior, is that enough to improve their overall driving behavior? Or do forward collisions and rear-enders make up substantially all of what the driver can control, so training the behaviors to reduce that type of near-miss reduces the driver's overall crash risk? To the point that it's similar to the safest tranche?

Is it that hard braking events are broadly indicative of surprises of lots of sorts, and so it happens that the only way to eliminate them all is to develop a full range of defensive driving habits?

More Goodhart's Law or Serenity Prayer?

Regardless of everything else, forward collisions are most likely to have the driver considered at-fault. Seems like reducing those in your insured population would reduce covered losses more than reducing collisions where your insured may not be at fault.

> Is it that hard braking events are broadly indicative of surprises of lots of sorts,

Of apparent surprises to the driver. And since actual, factual surprises are extremely rare, if a driver is regularly being surprised, they're a bad driver.

How does one not already know that they had a hard braking event? Surely the jamming their foot on the brake pedal and the rapid deceleration would send an even more obvious signal than playing a chime?

Obviously people know, but theres no impulse to introspect on why or how. Knowing that someone else knows you had a hard braking event taps in to our social brains to provide a much stronger response to the event. When we know people are watching we're more likely to try and justify our behaviour.

that is fascinating

Have you used one of these apps before? They capture a lot more than emergency stops, what I would classify as the above normal brake effort but not hard braking. Im sure the data exist to set the cutoff but its a lot more than “jam your foot on the pedal braking”.

It’s still out of the norm braking for my style of driver but from what I see on the road, people drive aggressively like this. Especially in the US.

What are these apps or devices? Where can I get one?

They are provided by your auto insurance company. A potential privacy nightmare, they track your movement. They also can get you a much lower rate.

If you don't want to go through your insurance company you can check out an app we built called RoadClub. You get points for safe driving behavior - and you can get the hard brake alerts. Is it a bit annoying? yes. You can't just drive agressively - you need to give space to slow down. I still struggle with it.

Your faq doesn't mention anything about location data. I'd like to try it, but want to know about that first.

A lot of people don’t realize that what they consider normal driving is actually aggressive driving by other metrics

I know way too many drivers who have exactly two modes: Full brakes and full accelerator. Like, they'll see someone in front of them, slam the gas pedal, and then when they get too close, slam the brakes to slow down. No in between. And they don't even know they're terrible drivers since they've always driven this way.

> We have apps that monitor driving and we play a tone to indicate that a hard braking event was detected. Simply letting people know that they had a hard braking event is an effective mechanism for behavior change (other companies have similar tech)

... How do people not notice that they are braking hard?

Because their definition of hard is not a slam on the pedal braking. It’s definitely out of the normal stopping but it’s not as hard as you might imagine. I could easily see people not realizing this.

Google Maps is definitely one of the technically coolest big tech products imo. It's fascinating what kind of non-obvious insights you can get from the combined user data (E.g. Crowdedness of public places, insights like in the article etc.)

What I find very interesting about it is how much data they have (and are able to collect).

I'm personally someone who is less worried about "privacy" for this sort of data. But I know lots of other people feel differently.

To me, this is a great example of the "greater good" for data sharing. But it is also a great example of responsible use of data.

The value of said data is tremendous, and could lead to great societal benefits if available for research.

So much so that I would argue that google (et al) should be compelled to make the data publicly available.

They have enough money, let's make society better.

They are making this data publicly available -- after aggregation and anonymization.

A fraction of the data they collect, to keep up appearances.

Publicly releasing 100% of the maps data they collect would be the most gigantic privacy violation the world has ever seen.

Are you seriously suggesting that google is gatekeeping the data because they care about privacy ?

this google research is a fascinating pivot from the usual driver-centric data we look at in insurance risk modeling. usually we use hard braking as a proxy for how safe an individual driver is. but using it to identify specific road segments or intersections with bad geometry is huge. it basically flips the script from individual liability to infrastructure-level risk assessment.

This is definitely pie in the sky but I dream of a future where you have so many autonomous vehicles all the road that we can not only collect this data but also incentivize the slow turning wheels of government to fix it.

yeah the interesting part is that the carriers already have most of this data from telematics apps, it's just sitting in corporate silos.

if we could bridge that gap, the economic incentive for municipalities would be massive lower accident rates mean less property damage and fewer expensive liability lawsuits for the city. it's basically a potential safety feedback loop that just needs the right data sharing protocol to actually kick in.

Ok but where is the public Maps overlay for this? Is it available?

Waze has this, and it works off of the same underlying data IIRC. It pops up a "history of accidents" note.

i'd love to see a safety heatmap layer, but the legal hurdles are probably massive. the second google puts a high risk badge on a specific road segment they open themselves up to lawsuits from local businesses or property owners claiming the algorithm is nuking their traffic or property value. it's probably going to stay in the hands of traffic engineers and underwriters for a long time.

Google is offering this as part of the geospatial platform that they market to governments for huge $$$ so I don't think you are going to get it for free any time soon. Maybe limited access if you have an Earth Engine developer account?

Table 1 and Figure 4: why are the Virginia controlled-access highways different? That population stands out in a way that smells like either a cultural difference or a policy difference.

I spend most of my time in California, have lived in SoCal and NorCal, and I spend a fair chunk of time driving around Virginia. My guess is that there's something fishy with the Virginia data being reported. Because if there is anyplace on earth with an insane number of controlled access roads, it's gotta be NVA/DC metro area (or the Tri-Border Area as I like to call it).

Also, they need to either update the caption for Figure 4, or move the plots to correspond with the caption. Clearly the Virginia data is on top (or the code is wrong, which seems exceedingly unlikely).

Speeding in VA just as you would in all other states literally becomes a criminal offense if you're caught. The data is reflective of that.

My gut tells me there's also another signal in the data. Soft braking events under conditions that call for acceleration. E.g. driver cannot process a highway merge in real time, so they slow down to have more time to think about what they should do next. Go!

I'd love to have a danger heat map displayed on a HUD while driving. Say a default green banner that goes red near a hot spot or even animates near a current hazard. Mostly it could use these same stats, but then be strident if anything unpredictable is detected nearby.

As I mentioned in another comment, Waze does this. There's a stretch of the Capital Beltway that, if it was on a race track and compressed, would be called "esses." It's totally fine to navigate at 80 MPH with no drama in any mechanically sound, post-1980 car, but it catches mediocre drivers by surprise. Waze throws up a "history of accidents" message whenever I drive through it.

Waze used to indicate transient road hazards (e.g. stopped cars, pot holes). It's in Google Maps now too (took them long enough) and I assume others.

Static hazards deserve physical signage and/or remediation.

Me too, that's a great idea. Or just incorporated into the satnav, better than getting the warning for an upcoming speed camera.

What is the actual use of this?

This research team used Google's first-party location data to identify San Jose's Interstate 880/US 101 interchange as a site with statistically extreme amounts of hard braking by Android Auto users.

But you don't need machine learning to know that... San Jose Mercury News readers voted that exact location as the worst interchange in the entire Bay Area in a 2018 reader poll [1]

It's not a lack of knowledge by Caltrans or Santa Clara County's congestion management agency that is keeping that interchange as-is. Rather, it's the physical constraints of a nearby airport (so no room for flyovers), a nearby river (so probably no tunneling), and surrounding private landowners and train tracks.

Leaving aside the specifics of the 880/101 interchange, the Google blog post suggests that they'll use this worst-case scenario on a limited access freeway to inform their future machine-learning analyses of other roads around the country, including ones where presumably there are also pedestrians and cyclists.

No doubt some state departments of transportation will line up to buy these new "insights" from Google (forgetting that they actually already buy similar products from TomTom, Inrix, StreetLight, et al.) [2]

While I genuinely see the value in data-informed decision making for transportation and urban planning, it's not a lack of data that's causing problems at this particular freeway intersection. This blog post is an underbaked advertisement.

[1] https://www.mercurynews.com/2018/04/13/101-880-ranks-as-bay-...

[2] https://www.tomtom.com/products/traffic-stats/ https://inrix.com/products/ai-traffic/ https://www.streetlightdata.com/traffic-planning/

> What is the actual use of this?

From the article:

"Our analysis of road segments in California and Virginia revealed that the number of segments with observed HBEs was 18 times greater than those with reported crashes. While crash data is notoriously sparse — requiring years to observe a single event on some local roads — HBEs provide a continuous stream of data, effectively filling the gaps in the safety map."

So we don't have to wait until an accident actually occurs before we can identify unsafe roads and improve them.

Actual use: autonomous vehicles know to be "more careful" here, perhaps to do "Jersey left" turns - right turn and U-Turn or other risk compensation strategies.

I'd love to see them incorporate visual detection of vehicle crash debris as well. There are two intersections in my area that consistently have crash debris like broken window glass and broken plastic parts and license plates from crashes. I know they are dangerous, but I don't know if autonomous vehicles also know that they are dangerous.

>No doubt some state departments of transportation will line up to buy these new "insights" from Google (forgetting that they actually already buy similar products from TomTom, Inrix, StreetLight, et al.) [2]

Google/Apple probably collect a massively larger amount of data than those other companies, putting those other companies at a risk of losing future revenue.

Between Google and Apple pretty much every car in the US is monitored.

Yeah, Google and Apple do probably have much more first-party probe data of passenger vehicles. But it really depends on the type of traffic data product. For some use-cases, it's more than sufficient for the vendor to buy probe data from specific types of fleet vehicles (like work trucks).

Where Google/Apple's coverage is quite valuable is for near-real-time speeds for atypical events -- say like yesterday's Super Bowl. But that's not what this blog post is about -- this post is about a well-established pattern that can be identified with historical datasets.

All that to say that vendors sell a wide variety of data products to transportation planners, but just because Google is now entering this niche market doesn't mean they'll be "the best" or even realize what their strengths are.

It does look much more like a revenue play. The data already exists, but not from the conglomorates and not as uniformly formatted.

Caltrans could lower the speed at that interchange, and use traffic calming to actually get people to drive slower. Good traffic engineering can still make a difference even with the existing physical limitations.

Absolutely nothing in this research suggests machine learning. All this is saying is that the hard braking events are associated with dangerous road segments that are well-known by other measures (in this case, reported crash rates).

On the interchange in question, they can always redo how the merge is designed in the same space. There is no excuse for that.

Please see:

> It's not a lack of knowledge by Caltrans or Santa Clara County's congestion management agency that is keeping that interchange as-is. Rather, it's the physical constraints of a nearby airport (so no room for flyovers), a nearby river (so probably no tunneling), and surrounding private landowners and train tracks.

The most recent budget estimate is $1bn for any changes to this interchange

$1B to avoid ending a lane before the intersection. Insane.

Indeed why would you even need this or a poll? The crash statistics already exist. What's the purpose of a proxy predictor unless the label is something too low signal to detect but may become a big issue later. The only such case is a new road that recently opened.

>unless the label is something too low signal to predict

>Also, crashes are statistically rare events on arterial and local roads, so it can take years to accumulate sufficient data to establish a valid safety profile for a specific road segment.

That is exactly what this article is about.

There’s a section of I-15 in Utah’s Salt Lake County which reliably has a crash on weekdays at 6pm. It was unfortunately at a pinch point in the mountains with no good alternate route… very annoying.

In a similar way that Google Maps shows eco routes, it’d be fun for them to show “safest” routes which avoid areas with common crashes. (Not always possible, but valuable knowledge when it is.)

That feels like it would cause induced demand for crashes though.

Too bad there's no map with such indicators, I'd definitely use it for my route planning, especially in unknown area. I usually know pretty well dangerous parts if I drive there frequently.

In unknown roads/highways I can predict hard bumps/gaps by seeing dark oil spots in the middle of each lane.

I'm really curious what their data looks like at the various racetracks and circuits. Fun fact; most raceways have accurate street-level indicators (including that they are one-way, but sadly they are not the best racing line) on most online maps, and my car did complain to me in its weekly report about a lot of hard turns, quick acceleration, and hard braking with helpful pins on e.g. Laguna Seca or Thunderhill corners.

In theory, the most dangerous turns would probably have higher variance on hard braking data.

When we worked at a p2p car sharing company it was well understood what a treasure trove that past accelerometer data was as good input to frequency prediction of a claim resulting from a particular rental.

Nice money they can made selling to insurers the collected data on who drives frequently on those road segments with high risk.

There's even no need to get the real names! To anonymously load person's risk coefficient, it's enough to ask to log in using Google account when buying insurance.

I considered writing an app you would take on a car ride that would record accelerometer readings indicative of a pothole. Geotag the reading and push is anonymously to a server.

Enough events should show clusters where potholes likely exist. You would think cities would love that kind of data.

This is a great use of this technology. In aggregate, these hard braking events _do_ tell us about road design issues. They also tell us about problematic drivers, in aggregate.

I'll never use one of these dongles, though, because I don't want my every move second-guessed. There's nothing _inherently_ dangerous about isolated hard braking or cornering or acceleration events. It all depends on context. Am I braking hard to avoid an obstacle or mistake by another driver? Is there someone behind me that's likely to rear-end me, or am I in the middle of a highway in the desert? Did I just replace my brake pads and I'm bedding in the new pads?

I don't want to have to worry about whether I've used up my invisible quota before the algorithm decides I should be moved into a more expensive insurance bracket.

> There's nothing _inherently_ dangerous about isolated hard braking or cornering or acceleration events.

I have to hope that the actuaries at the insurance company are well aware of that. Tuned correctly, the algorithm should not unfairly penalize you.

I am reminded of my mother-in-law. She has very few at fault accidents in her decades of driving. And yet she has been involved in a statistically unlikely number of major wrecks. She would say that she is a safe driver, because she is not found at fault. I think it more likely that she is an unsafe driver who creates situations where accidents are more likely to occur but in a way that will not peg her as the underlying cause. Her rates should go up. As should yours, if you are experiencing a very abnormal number of hard-braking events even though you can ascribe every one of them to something outside of your control. Because the implication is that something about your driving habit is increased risk.

As far as I understand, many not-at-fault accidents DO make one's rates go up. The rationale being "the places she drives are extra dangerous and puts our client at risk, despite driving properly."

How happy would HN be if, instead of buying location data as an end run around the 4th amendment, states and municipalities bought traffic data and used it to make safer streets and highways?

Not surprising but it is nice to have these data streams to explore locations that could potentially be remediated. I think anyone who drives interstates in metro areas would agree cloverleaf interchange are generally terrible with any significant traffic. Add in the general proclivity to drive much higher than the posted speed limit and these become dangerous due to the speed differentials and we've known this for 50 years.

"A 1974 study by Hall and Dickinson showed that speed differences contributed to crashes, primarily rear end and lane change collisions"

Hall, J. W. and L. V. Dickinson. An Operational Evaluation of Truck Speeds on Interstate Highways, Department of Civil Engineering, University of Maryland, February, 1974.

Against inferential statistics: https://hdl.handle.net/2381/37564

PDF download: https://iase-pub.org/ojs/SERJ/article/download/215/119/726

Defensive driving. Two hands, eyes on the "road", not caring about fools and maintaining safe distances. You have all the time in the world... I Recommend taking your car to a HPDE event, sometimes insurance will discount you for this. In this case, hard braking, is you just not knowing anything about your car or the cars around you... I barely use my brakes, but I also drive manual... Id say learn engine braking but y'all probably driving those stupid over powered electric cars...

https://donmcminn.com/2020/02/we-judge-ourselves-by-our-inte...

> information from the Android Auto platform

Can the quantity and length of tire marks on tarmac be used as a proxy for HBEs?

Hard braking could be detected externally; you can tell when vehicles are braking hard from the deceleration and suspension effects, without any surveillance equipment installed in them.

That's not gonna be something Google would research, of course, due to next to no alignment with their interests.

How long until my insurance company can figure out my commute route and adjust my rates based on the collective risk of the segments?

Or it could suggest a less risky route and offer you a discount in exchange for taking that route instead.

Why can't Gooapple suggest this today?

It seems that they could, but don't.

OK, now that you have this data, give me a "prefer safer routes" option in Google Maps navigation!

While you're at it, give me an option to avoid unprotected left turns and to avoid making a left turn across a busy road where cross traffic does not stop. (But only during heavy traffic; it's fine when nobody is on the road.) Not only are these more dangerous, they're also more stressful and they also introduce annoying variation into my travel time.

I think Lyft already does this for their driver navigation.

Wait, what do they teach in North America? Never heard the term "following distance" before now. Sounds misleading.

In Britain at least we call it "braking distance" and you're supposed to leave 2 seconds at least between you and the person in front. Count it off a lamp post/sign etc.

In certain at-risk areas they use chevrons on the road and signs telling you to keep at least 2 chevrons between you and the car in front.

People definitely always get into my braking distance in slower moving traffic, so that happens here too of course. But when things are moving well I likely push the limit and am generally moving faster than most others: going by GPS speed vs speedo, pushing a little into the discretionary and unofficial +10% guidance etc. And weirdly enough I do this for safety and fuel economy.

I generally prefer to avoid other vehicles as much as possible in all situations. But I was a motorbike rider in my youth. Once a defensive driver...

From that perspective, following distance sounds way more like a gap I want to close up than braking distance does.

Braking distance and following distance are two distinct things.

Following distance is the rule that you should leave a 2 second gap in front of you. That is often less distance than the braking distance.

You should be always able to see that your braking distance is or will be clear, and that sets the maximum speed you should drive at as you approach areas with reduced visibility, like corners or the brow of a hill. You must learn braking distances for the driving test.

> In Britain at least we call it "braking distance" and you're supposed to leave 2 seconds at least between you and the person in front. Count it off a lamp post/sign etc.

Indeed, that is the usual definition in the US for following distance. Along with a typical example of how to determine it for yourself.

We usually use the term braking distance to describe the distance that would be required to stop the car based on current conditions and speed. This is not necessarily going to be the same as the following distance.

Thanks for the reply. So then how is following distance determined? It would have to be further than braking distance to be at least as safe?

I do not know how they came up with the 2-4 second following distance recommendation. As you point out, this is in line with what the UK recommends as well. Probably it is a compromise between safety and practicality.

> It would have to be further than braking distance to be at least as safe?

Other way around. Following distance can be less, because the guy you are following cannot stop instantly unless he hits an immovable object or gets into a head-on crash. If he panic stops, then as long as your car performs similarly in braking you just need to have enough distance to allow for your own reaction time.

AFAIK braking distance for most cars is around 5 seconds at highway speed. Few people routinely set their following distance that long.

Dude the fucking 101S/808S connector is atrocious on so many levels.

what I thought when I read the article: wait, what? they're collecting this information over my phone from my car!?

eventually got me to this: https://arxiv.org/abs/2409.15561 maybe interesting for someone whos privacy focused.

Like another poster said, this is very well known already. It's one of the reasons why municipalities purchase this data from data brokers.

I for one am very glad manual driving is being phased out!

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There are only two conditions under which I have had to hard brake in more than 30 years of driving:

1. I'm on a race track or back road enjoying curves 2. Some asshole did something stupid in front of me.

I agree that hard braking is an accurate metric for road segment crash risk, but what I find upsetting is that insurance companies that use vehicle data treat /all/ hard braking equally. In reality, the risk is caused not by every person who hard brakes, but by the first person in a line of cars that hard brakes.

More on #2 above is that my observation has been MOST of the time, the braking was COMPLETELY unnecessary. Often the person hard braking that starts the chain has absolutely nothing in front of them to the horizon and is probably on their phone watching TikTok, suddenly looked up and realized they were driving and braked as a spooking reaction. This happens, observably, so often that there are active conspiracies on the Internet that the government hires people to drive like assholes to cause traffic. Obviously that's complete bunk, but my observation here is certainly not unique.

Rather than spying on everyone using our vehicle data to charge us ever more money (I've had zero at-fault accidents in nearly 30 years of driving, but my rates only go up), maybe we should enforce attentiveness on the road and start punishing those who are left-lane hogs (causing many lane changes, which are also risky), on their phone, or drunk. It's really obscene these days driving on American roads, it seems like everyone drives markedly worse since the pandemic /and/ enforcement has gone to nothing. The only time I see people get pulled over now is in speedtrap small towns.

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