Hard-braking events as indicators of road segment crash risk
research.google155 points by aleyan 6 hours ago
155 points by aleyan 6 hours ago
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.
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.
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.
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.
If you do it on the regular, or even occasionally, sure, but emergencies are emergencies.
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.
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.
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.
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 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 ).
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.
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 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.
> 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.
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!
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 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
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.
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.
While leaving space is nice, the person on the highway already typically has right-of-way.
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.
Another trick that works is just to let the windshield get cracked once. Then it will be immune to further rock strikes.
#trustmebro
Wow, I didn't know that was a thing. Been driving nearly 30 years, and never had a windshield chip.
Do you have a wood surface nearby? I would recommend giving it a good knock.
> 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.
> 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.
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. )
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.
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.
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.
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.
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.
There was a bike light that projects a bike lane onto the road, not sure why they are not more popular.
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.
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.
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.
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 :)
Thanks for sharing. I'm genuinely impressed to hear someone publicly share a story of growing self awareness and improvement.
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
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.
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.
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%.
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 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!
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
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.
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.
> 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.
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.
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.
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.
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.
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.
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'm always surprised at the number of people that follow too closely.
This always stuck with me
As one of my friends put it - driving in the US is like being in Whacky Races.
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.
The problem with increasing your following distance though is now you get other drivers cutting in, and you’re back to where you started
> 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.
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.
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.
(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.
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.
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.
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.
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.
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.
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.
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 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.
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.
A seasoned motorcycle rider should be unable to rip out any hair, due to safely wearing a helmet!
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.
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.
There might be, if the at-fault driver is uninsured and you are carrying uninsured motorist coverage.
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.
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.
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
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.
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?
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.
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.
A lot of people don’t realize that what they consider normal driving is actually aggressive driving by other metrics
> 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.
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.
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.
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?
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?
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.
Me too, that's a great idea. Or just incorporated into the satnav, better than getting the warning for an upcoming speed camera.
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.
Against inferential statistics: https://hdl.handle.net/2381/37564
PDF download: https://iase-pub.org/ojs/SERJ/article/download/215/119/726
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.
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.
I for one am very glad manual driving is being phased out!
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.)
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.
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.
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.
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.
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.
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.
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.
Dude the fucking 101S/808S connector is atrocious on so many levels.
Like another poster said, this is very well known already. It's one of the reasons why municipalities purchase this data from data brokers.