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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)
There are phantom traffic jams where someone breaks hard and it ripples on for ages. You can see on YouTube.
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.
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.
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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.
