Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Hard-braking events as indicators of road segment crash risk

research.google

Post reply on HN
Print view View original

521–530 of 577 posts

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

#521

Post by alistairSH »

lordloki wrote: post #487
ehnto wrote: post #326

Earlier quoted context omitted.

Slow down a bit to create another buffer. You can even do this before they have merged, as part of the bit where you allow them to safely merge. I think if you reflect a bit you'll find you are being the same kind of person as them, if you are getting angry that you have to slow down and give up space for someone else. I understand some people can be aggressive though, that can be frustrating regardless of the outcom…

-Slow down a bit to create another buffer. Now you've just created a shockwave traffic jam.

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

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

#522

Post by lazide »

bluGill wrote: post #518
lazide wrote: post #480

Earlier quoted context omitted.

In high traffic you’re definitely being screwed - both by the continuing lack of a proper safety gap, and by not being able to go a normal speed. Which does add up in many of these situations. But I guess we should just all self gaslight to feel better about it?

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

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

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

#523

Post by mnw21cam »

CGMthrowaway wrote: post #486
mnw21cam wrote: post #436

Earlier quoted context omitted.

This assumes that a 2 second interval is appropriate for all travelling speeds. This assumption is untrue at very low speeds, particularly when it takes longer than 2 seconds for a car to pass a point. For instance if we assume cars are 4m long, then with an interval of 2 seconds the cars would be touching at 4.47mph The assumption is also untrue at very high speeds. You'll want a larger gap. That's partly because at…

By 2 sec following distance I am referring to their back bumper to your front bumper. So cars "overlapping" in your example is not possible If you want 4 sec gap at higher speeds that's fine, the formula is speed-independent for throughput, not speed-independent for following distance. If you want 4 seconds at high speed then use 4 sec instead of 2 sec (i.e. 1 car/ 4 sec) >There's also the issue of speed oscillations…

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

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

#524

Post by angiolillo »

CGMthrowaway wrote: post #359
crazygringo wrote: post #340

Earlier quoted context omitted.

> If you choose to go in the fastlane in traffic you should understand that it will have people who do not care about the following distance as much and are just trying to go as fast as possible. It's not about choosing to go in the fast lane. It's about the fact that in heavy traffic, you have no idea which lane will be fastest, because they're all heavy and which one is fastest keeps switching. > I have found that…

This is a long thread of people talking past each other. The bottom line is simply this: if you want to drive with a larger-than-average following distance (call it whatever you want, a safety buffer, a "proper" following distance, the point is it is a distance less than the average following distance of the other drivers on the road) then you have to accept that you will not be able to drive at the same speed as the…

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

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

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

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

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

#525

Post by littlestymaar »

alt227 wrote: post #512
littlestymaar wrote: post #510

Earlier quoted context omitted.

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

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

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

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

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

#526

Post by CGMthrowaway »

mnw21cam wrote: post #523
CGMthrowaway wrote: post #486

Earlier quoted context omitted.

By 2 sec following distance I am referring to their back bumper to your front bumper. So cars "overlapping" in your example is not possible If you want 4 sec gap at higher speeds that's fine, the formula is speed-independent for throughput, not speed-independent for following distance. If you want 4 seconds at high speed then use 4 sec instead of 2 sec (i.e. 1 car/ 4 sec) >There's also the issue of speed oscillations…

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

Totally.

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

#527

Post by alt227 »

littlestymaar wrote: post #525
alt227 wrote: post #512

Earlier quoted context omitted.

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

I can't tell about the UK, but it's definitely true as well in France and Germany. And a quick look at map of London and Birmingham suggests that it may very well be the case in the UK as well…

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

I'll get you started:

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

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

#528

Post by CGMthrowaway »

maerF0x0 wrote: post #511
CGMthrowaway wrote: post #374

Earlier quoted context omitted.

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

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

Thanks. (sarcastic)

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

#529

Post by angiolillo »

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…

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

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

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

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

#530

Post by adw »

throwup238 wrote: post #391
adw wrote: post #390

Earlier quoted context omitted.

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

As far as I know that’s the law in every state I’ve driven in, but enforcement is pretty much nonexistent. Some states like Texas or Louisiana might have signs reminding people to stay out of the inner lanes except for passing but I’ve never heard of anyone getting a ticket over it. What’s enforcement like in the UK? For example, the specific law in California: https://leginfo.legislature.ca.gov/faces/codes_displaySe…

Vigorous.
Post reply on HN