YoSoySnekBoi@kbin.earth 21 hours 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.
agamemnonymous@sh.itjust.works 16 hours ago
Sibbo@sopuli.xyz 21 hours ago
Do you know of a paper that describes this kind of traffic motion?
oddlyqueer@lemmy.ml 20 hours 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 20 hours 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!
kubica@fedia.io 20 hours 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:
WhiteOakBayou@lemmy.world 20 hours 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 20 hours ago
It’s a great cover story until he meets someone at a party who loves that shit.
blarghly@lemmy.world 19 hours ago
It’s kind of funny. The writers probably thought traffic pattern analysis is boring because everyone hates traffic. Actually traffic pattern analysis is interesting because everyone hates traffic.
marzhall@lemmy.world 14 hours 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
kryptonianCodeMonkey@lemmy.world 20 hours 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 20 hours 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.
AA5B@lemmy.world 19 hours ago
Yeah, maybe I’m fooling myself but it really seems like hanging back more makes me have to do more sudden braking. Traffic seems smoothest when I’m close enough to discourage cut-ins …. Even if that means Im more at the mercy of traffic in front flowing down a bit
kryptonianCodeMonkey@lemmy.world 20 hours ago
You need to give even more space then so that them doing that doesnt make you slow down. People cutting in front of you also helps because those are the assholes causing the brake waves.
aesthelete@lemmy.world 18 hours ago
I have adaptive cruise with a settable car length and increasing the gap length just makes the cars behind you act more deranged.
I’ve found the only setting that doesn’t make everyone around me fly off the handle is the lowest (one car gap) setting.
I also drive in the diamond lane on long trips and typically have my upper speed limit set well above what the person in front of me is driving.
lemming741@lemmy.world 18 hours ago
At that point, you’re the guy doing 15 mph under the limit in the left lane.
Please only attempt this in the right lane.
fleck@lemmy.world 18 hours ago
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.
timik_pipik@lemy.lol 14 hours ago
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)
lightnsfw@reddthat.com 15 hours ago
Nah, cops being on the highway is one of the big causes of traffic. Everyone slows down to the speed limit when they come up on a cop and many are too timid to pass at all. This causes a huge brake wave and fucks everything up. It’s why I don’t think speed limits should even be a thing or should at least be adjusted because most highways are so low that just about everyone ignores them (and is not harmed doing so) until law enforcement appears. If people want to go slower that’s fine but they need to keep right when they aren’t passing and everyone needs to leave plenty of space in front of them so that traffic is permeable enough that people can get to their exit without causing brake waves and absorb the “shock” when it is necessary for someone to hit their brakes.
Cactopuses@lemmy.world 15 hours ago
This is about 2 decades old now but a bunch of people tried something sorta like a pacing car www.youtube.com/watch?v=OoETMCosULQ
5too@lemmy.world 15 hours ago
I feel like regular patrol cars might work like this already - who’s going to blow past a cop driving down the road?
socsa@piefed.social 14 hours ago
Then leave another gap. There are finite idiots in the world, and you cannot actually go backwards.
brbposting@sh.itjust.works 18 hours ago
I feel that
Works for me even with cut ins, gets easier with practice I’d say! Couple interesting YouTube videos on it, one here:
trafficwaves.org
WanderingThoughts@europe.pub 20 hours ago
Nicely demonstrated here: youtu.be/Suugn-p5C1M
wetbeardhairs@lemmy.dbzer0.com 20 hours ago
I couldn’t even see the traffic start because the fucking “Related Videos!” popups. God I hate what youtube has become.
Omgpwnies@lemmy.world 19 hours 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.
kryptonianCodeMonkey@lemmy.world 19 hours ago
So, I don’t know exactly how the adaptive cruise control works. But if it is slowing down and speeding up to maintain a specific distance, that does not fix things. The idea is to maintain a specific speed such that, as the people in front of you accelerate and brake, speed up and slow down, you have enough distance to not have to do that. You should essentially match their average speed with enough gap that their braking doesn’t put them close enough to your bumper that you have to slow down yourself. Normal cruise control would be better (except mine won’t set at speeds under, I think, 20mph) because your speed wont change. Adaptive cruise would make your drive safer, maybe, keeping you from being too close or failing to react to the change in traffic speeds, but I dont think it would solve the traffic issue itself.
Omgpwnies@lemmy.world 17 hours ago
It’s not “locked” to a specific distance, it’s fairly elastic and the exact follow distance varies based on speed. So, if traffic slows down, it will gradually close the gap while also slowing down. The end result then is far less drastic speed changes.
aesthelete@lemmy.world 18 hours ago
You aren’t solving traffic as an individual driver anyway. Sorry to burst everyone’s atomized bubble here but that’s complete nonsense.
If you manually maintain a large gap in front of you, everyone behind you becomes complete weirdos.
We could “solve traffic” by not requiring single occupant car drives to accomplish everything in our daily lives.
HalifaxJones@lemmy.world 16 hours 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.
calcopiritus@lemmy.world 15 hours ago
You think drivers from your <country/state/city> are bad? That’s because you have never driven in my <country/state/city>
HeyThisIsntTheYMCA@lemmy.world 15 hours ago
huh, they seem to get that concept on the highways i drive on. big state though, we could live ten hours apart from each other.
HalifaxJones@lemmy.world 11 hours ago
Haha true! I’m talking about Southern California. Los Angeles and Orange County.
socsa@piefed.social 14 hours 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 18 hours ago
Preach truth, Krypty