Hard-braking events as indicators of road segment crash risk • Hacker News Board

Re: Hard-braking events as indicators of road segment crash risk

#51

Post by yial » Mon, Feb 09, 2026, 6:27 PM UTC

mountain_peak wrote: post #46

presidentender wrote: post #20

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 goo…

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 Am…

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.

Re: Hard-braking events as indicators of road segment crash risk

#52

Post by infecto » Mon, Feb 09, 2026, 6:28 PM UTC

sigseg1v wrote: post #26

avidiax wrote: post #9

Earlier quoted context omitted.

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…

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 follo…

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

Re: Hard-braking events as indicators of road segment crash risk

#53

Post by MisterTea » Mon, Feb 09, 2026, 6:28 PM UTC

presidentender wrote: post #20

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 goo…

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.

Re: Hard-braking events as indicators of road segment crash risk

#54

Post by SoftTalker » Mon, Feb 09, 2026, 6:28 PM UTC

duderific wrote: post #43

sigseg1v wrote: post #26

Earlier quoted context omitted.

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 follo…

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.

Re: Hard-braking events as indicators of road segment crash risk

#55

Post by mountain_peak » Mon, Feb 09, 2026, 6:29 PM UTC

amanaplanacanal wrote: post #50

mountain_peak wrote: post #46

Earlier quoted context omitted.

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 Am…

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?

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.

Re: Hard-braking events as indicators of road segment crash risk

#56

Post by SoftTalker » Mon, Feb 09, 2026, 6:30 PM UTC

garaetjjte wrote: post #22

kube-system wrote: post #10

Earlier quoted context omitted.

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?

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

Re: Hard-braking events as indicators of road segment crash risk

#57

Post by amanaplanacanal » Mon, Feb 09, 2026, 6:30 PM UTC

AngryData wrote: post #39

garaetjjte wrote: post #22

Earlier quoted context omitted.

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

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.

Re: Hard-braking events as indicators of road segment crash risk

#58

Post by amanaplanacanal » Mon, Feb 09, 2026, 6:32 PM UTC

infecto wrote: post #12

pavel_lishin wrote: post #4

Earlier quoted context omitted.

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.

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 b…

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.

Re: Hard-braking events as indicators of road segment crash risk

#59

Post by infecto » Mon, Feb 09, 2026, 6:32 PM UTC

munificent wrote: post #31

harshaw wrote: post #2

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 braki…

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.

Re: Hard-braking events as indicators of road segment crash risk

#60

Post by yial » Mon, Feb 09, 2026, 6:33 PM UTC

amanaplanacanal wrote: post #50

mountain_peak wrote: post #46

Earlier quoted context omitted.

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 Am…

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?

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.