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

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

#571

Post by alt227 » Thu, Feb 12, 2026, 7:48 PM UTC

LazyMans wrote: post #549

alt227 wrote: post #542

Earlier quoted context omitted.

Exactly, and that same theory also applies to long slow breaking as well. What you are refering to is the well known phenomenon of traffic waves or phantom jams. The UK has all but eliminated them with variable speed limits without the need to make every leave half a mile gap between each car. https://nationalhighways.co.uk/road-safety/variable-speed-li...

We have variable speed limits on parts of our roads. People commonly exceed the stated limit by 20+ mph since they're used to "full speed" and ignore the instances where it's being reduced. I welcome our future robot car overlords where all of these problems should in theory be greatly reduced or eliminated entirely.

Where I live it is impossible to exceed the variable speed limit because every other car on the road is doing it.

I agree, a full network of self driving cars which can all move together in a chain will eliminate this problem. I just hope I live long enough to see it.

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

#572

Post by littlestymaar » Fri, Feb 13, 2026, 4:51 PM UTC

alt227 wrote: post #527

littlestymaar wrote: post #525

Earlier quoted context omitted.

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...

Funny how you don't even bothered to get the data by yourself get still felt entitled to act like a jerk.

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

#573

Post by cryptonector » Sat, Feb 14, 2026, 8:09 PM UTC

alt227 wrote: post #462

cryptonector wrote: post #345

Earlier quoted context omitted.

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 yo…

> 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.

What? Your travel time does not get longer, and if the traffic is merely slow then this "leaving your engine running for more of the time" is nonsense. Even if it's stop and go and you have a car that kills the engine every time you come to a dead stop, that will use more gas because you're making inefficient use of the electrical system (charging and discharging the battery more than you should have to).

> Also you then just leave a bigger gap in front of you for somebody to jump into,

Sure, so as earlier you have to pay attention and not allow that.

> 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

Doubt.

And besides doubting your claim about efficiency, you're doing exactly that which most helps the pressure wave endure, and thus you're causing more delays for more people, and more people to have to brake hard, and more engine stop/start cycles, all of which means more pollution overall not less, etc.

You really have to think systemically.

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

#574

Post by ehnto » Sun, Feb 15, 2026, 7:34 AM UTC

alistairSH wrote: post #447

ehnto wrote: post #367

Earlier quoted context omitted.

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 frustrati…

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.

Oh I agree, I mean there was no solution to traffic in my comments.

I do think some don't appreciate that it is not an anti-car stance to wish for less car dependant cities. You still get to have a car, and commuting by car should be easier if you need it, since there is less demand on the limited resource that is the road network.

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

#575

Post by maybewhenthesun » Mon, Feb 16, 2026, 10:24 PM UTC

apparent wrote: post #567

maybewhenthesun wrote: post #563

Earlier quoted context omitted.

It is possible of course that the highways you drive are just too busy and the max speed is actually set too high for how busy the road is. That happens more than you'd want because lowering the max of a highway is always an unpopular thing to, even if it's needed. Still, I tend to find that people underestimate the danger of short distances. Often it's just better to accept a 100 cars going in front of you than to s…

This assumes that you can actually maintain a 3 second follow distance. On some roads, you simply cannot, and an attempt to maintain such a distance leads to increased danger from all the cars that cut in. Simply put: follow distance is not a unilateral decision.

That's what I mean with 'the road is too busy'. If you can't maintain a 3 second distance the speed needs to go down until you can. But you are right that this is sadly not something you can always do on your own.

I'm still convinced people decide way too soon that the 3 second distance is more dangerous. You might be right if people are constantly cutting in the moment you leave a gap, but if someone cuts in every 5 minutes you're still safer off with the gap.

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

#576

Post by xnx » Sun, Feb 22, 2026, 8:09 PM UTC

_carbyau_ wrote: post #241

radlad wrote: post #101

Earlier quoted context omitted.

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…

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.

What if you're a safer driver than most and tired of subsidizing maniacs?

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

#577

Post by xnx » Sun, Feb 22, 2026, 8:12 PM UTC

coredog64 wrote: post #129

hiq wrote: post #67

Earlier quoted context omitted.

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.

2 sides to hypermiling:

1) Maintain a safe distances so you touch the brake as little as possible

2) Follow so close to the other car that you draft behind them (not recommended!)