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Hard-braking events as indicators of road segment crash risk

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

#451

Post by ninalanyon »

yial wrote: post #97
Noumenon72 wrote: post #88

Earlier quoted context omitted.

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 ar…

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 m…

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

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

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

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

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

#453

Post by ninalanyon »

ErroneousBosh wrote: post #141
NitpickLawyer wrote: post #90

Earlier quoted context omitted.

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.

There's a couple of bits of motorway in England with that, I'm pretty sure the M6 and the M1. There are white chevrons painted on the road and you keep two of them between you and the car in front. Also "Keep Two Chevrons Apart" is going to be the name of my specialist Citroën breaker's yard.

And on the M5 between Gloucester and Bristol.

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

#454

Post by hansvm »

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

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

#455

Post by ninalanyon »

bjackman wrote: post #429
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…

I find that respect for safe following distance varies quite a lot amongst the places I've driven. E.g. - Switzerland and (somewhat surprisingly) UK: pretty good, people doing idiotic shit is rare enough that I'll usually comment on it if there's another person is in the car. If someone is riding my ass I'll make the effort to try and shake them off. - Italy and Spain: horrifying, impossible to relax at all on the hi…

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

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

#456

Post by ninalanyon »

apparent wrote: post #330
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…

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

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

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

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

#457

Post by alt227 »

littlestymaar wrote: post #397
bramblerose wrote: post #378

Earlier quoted context omitted.

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

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

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

The main issue is highways and rural roads.

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

#458

Post by ninalanyon »

bsder wrote: post #238
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…

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

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

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

#459

Post by wiredfool »

closewith wrote: post #446
HPsquared wrote: post #403

Earlier quoted context omitted.

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

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

I wish.

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

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

#460

Post by alt227 »

OneOffAsk wrote: post #140

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 "…

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