- cross-posted to:
- fuckcars@lemmy.world
- cross-posted to:
- fuckcars@lemmy.world
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Most traffic jams actually act as a kind of compression wave moving backwards through traffic. Something as small as a squirrel running across the road can cascade into an hour-long jam.
One person brakes, then the person behind them, then the person behind them, but each time they are getting closer to each other (nobody stays equidistant from the car in front of them when braking). This causes a greater and greater slowdown as more cars are compacted into a tighter space, which travels backwards in traffic like a wave. Often the person who caused it doesn’t even realize anything happened.
A lot of mapping software actually estimates a given traffic slowdown by treating traffic as a fluid with a wave moving backwards through it.
That’s also why the best way to relieve traffic is to go at a slow even pace without braking. Every time the someone in heavy traffic runs up the ass of another car and brakes hard, or swerves into the “faster” lane and make someone else brake to not hit them, they cause another brake wave. If you have a few cars intentionally just hanging back and cruising with a big enough gap between them and the cars jocking for position in traffic in front of them, then their brake waves do not propogate behind you and eventually traffic just picks up pace again.
Edit: side bonus, you still get there just as fast, but with a lot less stress fighting assholes for position (minus the ones who fly past you thinking you’re the asshole for not riding someone else’s bumper)
Yeah, in theory it’s great but every time I try it people just cut in front of me then slam on brakes causing me to have to brake then adjust then repeat ad nauseam. People suck.
This is why I thought that maybe it would be good to have some kind of pacing cars, e.g. operated by traffic police? I.e. when you already know or can anticipate that there is a large jam building up, you bring in one pacing car on every lane at an appropriate low speed and everyone has to adjust, so the thing you mentioned won’t happen.
Or we could just build trains and other alternatives to cars, which would end up cheaper, faster, safer, environmentally friendly, …but we have big oil.
(Sry, I had to)
Hey I studied this in grad school for a bit, and it really is just “someone does some dumb shit which leads to a cascading wave of additional people doing dumb shit which propagates backwards for miles.” Basically when the offered load is getting close to the maximum load, all it takes is one person aggressively changing lanes to throw that section of highway into gridlock, and it will remain that way until the total integrated traffic flux across that incident boundary again falls below the critical offered load inflection point.
Basically, pick a lane and just stay in it. Maintain proper following distance. Counterintuitively, the following distance should be for the speed you want to drive, so even in traffic it should be like 5+ car lengths even though you are going slow. This is because it reduces the offered load, and once that number falls below the critical point, speeds will increase again. Bumper to bumper traffic basically prevents that from happening because it dampens the ability for a “speedup” wave to propagate.
Of course this is all impossible for humans. All it takes is a few idiots to throw off the balance.
So basically: 1. Put people in public transport away from the steering wheel, 2) scale back cars use.
Go back to fuckcars with the rhetoric.
Yep! All it takes is one person braking, and then the person behind braking, then the person behind them, and eith each braking the overall speed slows down more and more. It creates a wave of traffic. The wave passes through. The starting point I think moves back further and further.
I think about it a lot while I sit in traffic.
There was a really interesting MythBusters episode where they essentially replicate what you’re talking about. Albeit with an “n” of 1 or 2 and a very small scale, but still interesting.
There are phantom traffic jams where someone breaks hard and it ripples on for ages. You can see on YouTube.
3 fucking seconds
The answer is a simple 3 second gap.
That’s it, just 3-mississippi (or 3-onethousand) seconds behind the car in front of you and most of the avoidable jams go away.
If you do that, someone will move into the gap. If someone moves into the gap you can slow down to make another gap to them, but then someone else will drive into that gap. I don’t know of any major city where you can maintain a 3 second gap during rush hour.
Even worse, if you ever brake to try to create a gap, you’re likely to cause a traffic jam behind you.
Sure, if everybody did follow the suggestion and allowed a 3 second gap you wouldn’t have traffic jams, but that’s just not human nature, apparently.
You’re totally right. It’s a social/culture issue. You doing this on your own isn’t going to do shit. Everyone has to miraculously decide to come together to solve the problem with no one taking advantage. It’s the same reason we can’t do anything about climate change.
Edit: I realize this came off as extremely dismissive about climate change. I still think we should do what we can to, at the very least, reduce effects. It was more just a realistic take of why I think we’re all fucked. I still avoid eating meat, single use garbage, and other wasteful shit, don’t get me wrong.
Can anyone tell me why this is being downvoted? I don’t really care about downvotes, Im more just wondering how I’m wrong.
Only ever have to ask, my friend
Heres an overview shot of a traffic pulse.
One person brakes for no reason which leads to everyone else braking. The pulse travels despite there being nothing there. The longer it can take for someone to start up again also can delay the whole thing.
Iirc, the answer is to have someone drive slowly and let other cars pass. It creates a buffer zone that regulates the flow back to normal pace. Or at least that’s what I remember from New Scientist’s video from like a decade ago.
I used to just idle when traffic moved. Slowed down way before i was even close to the car ahead. Played a game where i was trying to move at a constant speed or max fuel econ. Much less stressful to always be moving than gas/brake every 10s, even if you’re moving 5mph.
Really helps to look 3-4 cars ahead for brake lights.
