Make it make sense
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.
YoSoySnekBoi@kbin.earth 2 weeks ago
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.
kryptonianCodeMonkey@lemmy.world 2 weeks ago
That’s also why the best way to relieve traffic is to go at a slow even pace without braking. Every time the someone 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 gao between them and the cars jocking in front of them, then their brake waves do not propogate behind you and eventually traffic just picks up pace again.
OR3X@lemmy.world 2 weeks ago
Yeah, in theory it’s great but every time I try it people just cut in front of me then slam in brakes causing me to have to brake then adjust then repeat ad nauseam. People suck.
WanderingThoughts@europe.pub 2 weeks ago
Nicely demonstrated here: youtu.be/Suugn-p5C1M
Omgpwnies@lemmy.world 2 weeks ago
Adaptive cruise control FTW. Matches speed with the person ahead of me (up to the max that I set) and maintains a gap that I can specify. It starts slowing down long before I’d notice the gap closing if I were doing it myself, so the +/- acceleration is a lot smoother as a result.
HalifaxJones@lemmy.world 2 weeks ago
Californians te the worst drivers in the world because none of them understand this simple concept. Every day I’m driving, I give more than enough space in front of me for someone to cut me off and I don’t have to brake. It’s simple. However, I’m constantly getting people riding my ass. Switching around me. And being over all menaces just because I’m leaving a roper gap between myself and the car in front of me. It’s wild.
socsa@piefed.social 2 weeks ago
Right, if you think about the creation of traffic as a negative speed wave which causes compression, and traffic alleviation as a positive speed wave which requires rarefaction, then it becomes clear why traffic is so stubborn. When people are so bunched together, no positive speed wave can propagate. Which is why you literally get to to the point where the original idiot slammed on the brakes and the traffic magically disintegrates. If everyone stayed 5 car lengths apart in traffic, that alleviation would actually propagate backwards as fast as the initial congestion.
brbposting@sh.itjust.works 2 weeks ago
Preach truth, Krypty
agamemnonymous@sh.itjust.works 2 weeks ago
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Sibbo@sopuli.xyz 2 weeks ago
Do you know of a paper that describes this kind of traffic motion?
oddlyqueer@lemmy.ml 2 weeks ago
Here’s the (abstract of the) paper I was thinking of pubsonline.informs.org/doi/abs/…/opre.4.1.42
Appalling that I can’t find a free version of a 70 year old paper. You might be able to find the full text somewhere… I would of course never encourage anything that might run afoul of the scientific publishing protection racket.
oddlyqueer@lemmy.ml 2 weeks ago
I couldn’t find the paper I was thinking of that described the phenomenon of traffic propagating as a pressure wave, but I did find this paper (new to me) that describes a model for simulating how congestion spreads in urban environments (as opposed to an isolated highway, which IIRC the paper that most people reference models). It does have the full text available though, and it looks like a good read and has references that should get you going on the history of congestion research.
I am not an expert; I just found this with a few minutes of searching. If there are experts with better papers I’d be happy to hear from ya!
www.nature.com/articles/s41467-020-15353-2.pdf
kubica@fedia.io 2 weeks ago
I knew about the elastic band effect, but I was unsure if it was considered the same. But searching that I found about both:
https://en.wikipedia.org/wiki/Accordion_effect
https://en.wikipedia.org/wiki/Traffic_wave
WhiteOakBayou@lemmy.world 2 weeks ago
In one of the Mission Impossible movies Tom Cruise is supposed to have a boring job no one will ask him about and the movie shows this by having the character talk about traffic patterns. I thought it was interesting information then and think it is interesting now.
frezik@lemmy.blahaj.zone 2 weeks ago
It’s a great cover story until he meets someone at a party who loves that shit.
marzhall@lemmy.world 2 weeks ago
Lmao I remember seeing this exact scene as a kid, thinking as he was talking “oh that sounds cool as fuck” and then only from how the scene played out realizing it was supposed to be a significantly boring concept