There are phantom traffic jams where someone breaks hard and it ripples on for ages. You can see on YouTube.
Make it make sense
Submitted 7 months ago by The_Picard_Maneuver@piefed.world to [deleted]
https://media.piefed.world/posts/Gy/NK/GyNKBqq9G1AjsIS.jpg
Comments
dependencyinjection@discuss.tchncs.de 7 months ago
RememberTheApollo_@lemmy.world 7 months ago
I find it’s the speeders, tailgaters, and the infuriating few that can’t seem to manage to go at the prevailing speed that cause the waves in traffic. The rest is structural - merges, construction, lane reductions, etc. The aforementioned all cause the slowdowns because they move quickly, traffic tends to follow, and end up constantly hitting their brakes riding the ass of the slower traffic. That starts a wave that ends up with traffic stopping when density is high enough.
You can’t control others moving slower than you want, bitching about lane campers changes nothing, but managing a speed/spacing that allows little or no braking does wonders to keep things moving. If only people would bother to do so.
Mr_Dr_Oink@lemmy.world 7 months ago
I used to say “Speeding gets you nowhere, fast” but the irony is lost on anyone that does it.
melisdrawing@lemmy.dbzer0.com 7 months ago
I think about this all the time while commuting. I yearn so much to teach the drivers this one simple trick!
buttnugget@lemmy.world 7 months ago
This is like saying you don’t know how a bottleneck works.
curiousaur@reddthat.com 7 months ago
Exactly, it’s entirely because the people in front of you are going slow.
l_isqof@lemmy.world 7 months ago
You are thr traffic.
badbytes@lemmy.world 7 months ago
Reaction times of humans.
Sam_Bass@lemmy.world 7 months ago
Traffic is a “thing” because the slowest common perambulator is always in front
bitwolf@sh.itjust.works 7 months ago
It all starts with someone in the passing lane, not passing, and one or more pissed off people behind them :)
dingus@lemmy.world 7 months ago
Yeah I drive around 3 hours on the highway every several weeks. Sometimes on my drive, there’s obviously traffic. A lot of times it will be something like rush hour traffic, a crash, construction, etc.
But then like…a good portion of the time when I come to the very front of the “clog”, I find that it is just a blockade of multiple people going incredibly slowly and taking up all lanes of traffic, refusing to move over despite the fact that they are going under the speed limit.
Korhaka@sopuli.xyz 7 months ago
People drive too close to each other, someone has to slow down and then the car behind slows down a bit more. Repeat until you get to the point someone completely stops. Then the next car stops for slightly longer.
If you leave a safe distance then it wouldn’t happen.
socsa@piefed.social 7 months ago
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.
thejoker954@lemmy.world 7 months ago
Sad thing is its more than just a few idiots.
The idiots are the majority. So stupidly self absorbed they constantly screw themselves over trying to “get theirs”.
N0t_Legal_Advice@lemmy.today 7 months ago
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.
LemmyZed@lemmy.ca 7 months ago
So basically: 1. Put people in public transport away from the steering wheel, 2) scale back cars use.
SereneSadie@lemmy.myserv.one 7 months ago
Go back to fuckcars with the rhetoric.
ftbd@feddit.org 7 months ago
“Pick a lane and stay in it” leads to slow drivers blocking the left lane, no?
socsa@piefed.social 7 months ago
From a purely traffic load perspective, the whole "fast lane" thing doesn't make a huge difference, and the aggressive obsession with it is actually a big part of the psychology which creates traffic in the first place. Traffic capacity is generally optimized when everyone is traveling close to the same speed and has enough following distance to safely maintain that speed, which is why speed limits are set for the slowest road users. Just in general, speed does not increase road capacity beyond a certain fairly low limit because it requires dramatically increased following distance, or in the absence of such responsible behavior, it massively increases the frequency of traffic disruption.
The worst case is a few people traveling much faster than the slowest road users, as these few users both take up more space, and cause more disruption. The "fast lane" concept is rooted firmly in an unfortunate behavioral reality and has basically no real scientific basis beyond that. Even if you had perfect robot drivers with perfect reaction time and the ability to see far ahead of themselves, the critical capacity speed only increases slightly because the maximum stoping distance is still limited by rubber and asphalt.
seralth@lemmy.world 7 months ago
You have demonstrated why fundamentally humans suck at driving and this problem is unsolvable.
Not because you asked the question but because it’s not intuitive why.
So long as this has to be explained to anyone it can’t be solved.
TheEighthDoctor@lemmy.zip 7 months ago
JargonWagon@lemmy.world 7 months ago
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.
mechoman444@lemmy.world 7 months ago
I think the issue is more or less slow drivers. One asshole is going 60 in a 70 in the left lane which caused people to pass them which in turn cause the cascade from the maneuvering around the slow person.
Slow drivers are far more dangerous than people don’t 10 15 over the speed limit.
Takios@discuss.tchncs.de 7 months ago
so even in traffic it should be like 5+ car lengths even though you are going slow.
Other drivers: “It’s free real estate”
Corn@lemmy.ml 7 months ago
Secret is to play the game next to a semi. Some semis kinda do it too by engine braking as they see the wave approaching
iThinkDifferentThanU@lemmy.world 7 months ago
slow speeds cause accidents, not speed, the sudden stop, cause of some inbred driver
Gustephan@lemmy.world 7 months ago
www.mdpi.com/2076-3417/11/9/4278
TLDR: modeling traffic as a gas leads to fairly accurate predictions. If that doesnt mean anything to you, here’s a decent visualization of how gasses move around in a system. In this analogy, each of the gas particles models a car on the road. youtu.be/Hr5Baj3lXFA
SreudianFlip@sh.itjust.works 7 months ago
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.
merc@sh.itjust.works 7 months ago
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.
SreudianFlip@sh.itjust.works 7 months ago
You attribute an uneducated, uncivil approach to human nature, but I have been in human queues around the world, and they vary hugely based on cultural and social differences.
What you think is human nature seems to actually be driving culture in your region.
Yesterday I had a swasticar driver actually let me in on a disorderly merge. I was amazed, it was a first. Clue: nothing about Hondas changes people to be better. Tesla and BMW drivers are just shittier at sharing. This is culturally allowed.
plyth@feddit.org 7 months ago
Teach people to drive on the right lane unless they want to overtake somebody. Whoever overtakes you on the left won’t drive into the gap because they also want to overtake whoever is driving in front of you.
NikkiDimes@lemmy.world 7 months ago
You’re totally right. It’s a social/culture issue. You doing this 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.
CannedYeet@lemmy.world 7 months ago
Except the person next to you or behind you gets frustrated and cuts you off and you have to hit the brakes and create a traffic pulse.
SreudianFlip@sh.itjust.works 7 months ago
Well yes, society functions only with cooperation. Uncivil behaviour ends with violence and dismay.
However 3s usually allows for slow adjustments which alleviate caterpillaring.
Stamets@lemmy.world 7 months ago
Only ever have to ask, my friend
Lemminary@lemmy.world 7 months ago
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.
untorquer@lemmy.world 7 months 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.
HeyThisIsntTheYMCA@lemmy.world 7 months ago
not slowly, just leave room
Hikermick@lemmy.world 7 months ago
It happens when people tailgate. They over react and it causes an according effect.
NikkiDimes@lemmy.world 7 months ago
Or when people drive too aggressively and cut someone off, causing them to slam on their brake.
Jax@sh.itjust.works 7 months ago
Nope that’s just a negative picture of a guy
lemming741@lemmy.world 7 months ago
George Carlin explains it pretty simply
lightnsfw@reddthat.com 7 months ago
The people at the front are morons and probably in the wrong lane.
NikkiDimes@lemmy.world 7 months ago
You don’t like driving 55 in the passing lane? You get such a great view of everyone flipping you off!
DarkAri@lemmy.blahaj.zone 7 months ago
Its because of two things. One is that people hog the passing lane or try to pass slowly so it takes them a few minutes to overtake a few cars, and also because people drive at different speeds. Some people drive at the speed that feels comfortable, orhers drive the state imposed speed limit. This creates pockets of dense traffic, and then people try to pass, but there is always the person who fries to pass as slow as possible because they are going a few mtoh over the speed limit already.
Its really just a bad combination of laws, and drivers who are terrified of breaking the law, and people who dont know how to drive correctly in a way to reduce traffic. Also mamy people are just never consider that others also need to use the roads.
NikkiDimes@lemmy.world 7 months ago
Hey, if you have some physical limitation or just aren’t comfortable going faster, that’s 100% fine. Stay the hell in the right lane and never leave it, thanks lol
justme@lemmy.dbzer0.com 7 months ago
Similar to en.m.wikipedia.org/wiki/Turbulence The gist of it is that once you reach critical density people can not drive homogenously anymore and (de-) accelerate constantly to not bump into the next car. The problem could be alleviated with self driving cars which negotiate a uniform speed.
kameecoding@lemmy.world 7 months ago
The problem could be alleviated with self driving cars which negotiate a uniform speed.
Other than the obvious public transit solution comment, you are aware that ACC exists right?
We literally have the technology on almost all cars to keep a uniform distance from the car in front of it, if people realized you can save fuck all time by speeding on your 30 mile commute we could have cars moving at the speed limit and just have smooth traffic flow without any need for self-driving
justme@lemmy.dbzer0.com 7 months ago
Geez… I didn’t want to write an entire essay and just mentioned ONE possible example for improvement, to illustrate my explanation. No need to get salty…
SwingingTheLamp@midwest.social 7 months ago
self driving cars which negotiate a uniform speed.
Until then, human drivers could approximate this system by all agreeing on a uniform speed. Maybe through some sort of app?
Or, this sounds crazy, perhaps the authorities could post signs by the side of the highway with the uniform speed printed on it?
justme@lemmy.dbzer0.com 7 months ago
That is actually a thing, but the optimal speed depends on traffic. Otherwise it always helps to lower speed limits, there are several studies in my area which show that on average everybody would arrive quicker at their destination if we reduce urban speed limit from 50 to 30 km/h.
chuckleslord@lemmy.world 7 months ago
Your solution is a dream. Real solutions already exist, it’s called mass transit.
justme@lemmy.dbzer0.com 7 months ago
It exists… Only in movies and games though;)
YtA4QCam2A9j7EfTgHrH@infosec.pub 7 months ago
The problem is solved by connecting all the cars, and putting them on rails that are electrified. This way you move fuel off site, and the cars are synced by the connection.
justme@lemmy.dbzer0.com 7 months ago
I was always dreaming about some kind of “individual public transport” (I think minority report had a nice example, because there the transport is part of your flat and thus doesn’t waste space when not moving), which interconnects into trains for longer distances. Currently it would probably be only freezable for Intercity ranges, otherwise the coupling process takes longer than the drive.
Also, you can charge electric cars through induction rings in the street, like mobile phones. The efficiency is not the best though.
ILikeBoobies@lemmy.ca 7 months ago
People changing lanes
If everyone stuck to the driving lane and only moved over to pass one car in front of them then there’d be less.
abbiistabbii@lemmy.blahaj.zone 7 months ago
basically it’s a thing with cars where if a single car slows down for any reason, even slightly, it causes a cascade effect that leads to traffic jams.
Yet another reason why cars suck.
infinitesunrise@slrpnk.net 7 months ago
It’s usually a complex crowd effect created by many participants trying to maneuver among each other in slightly disperate ways.
In Portland OR, it really is because some dingbat slowed down to 20 MPH on the interstate for literally no fucking reason at all.
MrQuallzin@lemmy.world 7 months ago
Taking I-5 into Vancouver from Portland is always horrific. Once you get over the bridge it always clears right up! A big part of that is all the on ramps. There’s so many of them! So everybody is having to make way every 10 feet for someone merging in.
It’s horrendous.
infinitesunrise@slrpnk.net 7 months ago
Yeah they could probably stand to lose the more southern of the two ramp sets at Delta Park, feels very extra and overall unhelpful. Of course ODOT’s solution, beyond replacing the bridge, is to widen I-5 south of the bridge - Which anyone with a brain and 50 years of highway traffic studies can tell us would directly contribute to worsening the problem.
blarghly@lemmy.world 7 months ago
Often they do this because their car is barely limping along and they are trying to make it to the next exit.
infinitesunrise@slrpnk.net 7 months ago
This driver is distinct from that driver. We definitely have those too, and they have my sympathies. But this driver is the one who just thinks to themself that it would be nice to go slow for a while, on a lark. Or they don’t think at all and in that brief 15 seconds of brain death their nerves stop sending signals to their foot to press the gas.
ininewcrow@lemmy.ca 7 months ago
It’s all a mad rush of people trying to get to where they don’t want to be as fast as possible
ieatpwns@lemmy.world 7 months ago
Bumper riders Lane switchers Brake checkers Ramp users switching lanes wayyy too late
UnderpantsWeevil@lemmy.world 7 months ago
Idk why they call it a bottleneck, when it’s a straight line through the opening of the bottle.
YoSoySnekBoi@kbin.earth 7 months 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 7 months ago
WhiteOakBayou@lemmy.world 7 months 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.
marzhall@lemmy.world 7 months 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
frezik@lemmy.blahaj.zone 7 months ago
It’s a great cover story until he meets someone at a party who loves that shit.
kryptonianCodeMonkey@lemmy.world 7 months 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.
socsa@piefed.social 7 months 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.
HalifaxJones@lemmy.world 7 months 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.
brbposting@sh.itjust.works 7 months ago
Preach truth, Krypty
Omgpwnies@lemmy.world 7 months 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.
OR3X@lemmy.world 7 months 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 7 months ago
Nicely demonstrated here: youtu.be/Suugn-p5C1M
Sibbo@sopuli.xyz 7 months ago
Do you know of a paper that describes this kind of traffic motion?
Wappen@lemmy.world 4 months ago
Not a paper but a great video I watched about it by braintruffle: youtu.be/m74zazYPwkY
oddlyqueer@lemmy.ml 7 months 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.
kubica@fedia.io 7 months 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:
oddlyqueer@lemmy.ml 7 months 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!
bobo1900@startrek.website 7 months ago
CGP grey did a video on it: www.youtube.com/watch?v=iHzzSao6ypE
Basically one car breaking too much will make the following brake even more and so on until one stops and there’s a jam. There is no clear reason like a road blockage or an accident, just compounding slow down.
merc@sh.itjust.works 7 months ago
Basically one car breaking too much will make the following brake
If the car in front of me started breaking, I’d definitely get out of the way.
kameecoding@lemmy.world 7 months ago
I’d recommend this video as a response to that one, cgp greys video is technically correct and fucking dumb at the same time
PhobosAnomaly@feddit.uk 7 months ago
A few years ago, I was bitching and moaning about a jam, and my pal just said “you’re not in traffic, you are traffic”.
I know it’s nothing more than a cheeky soundbite but just reframing it like that and knowing I’m part of the problem rather than the exception has made me a lot calmer on slow moving roads.
Plus it has encouraged me to either use public transport more, or just drive to a park-and-ride a mile or three out, and run the rest - facilities permitting of course.
iAmTheTot@sh.itjust.works 7 months ago
99% of traffic like this is caused by people following too closely.
TomMasz@lemmy.world 7 months ago
Years ago I was in LA on business and ended up on I-5. All of a sudden traffic stopped dead. Eventually people were getting out of their cars and walking around. About a half-hour later, traffic started up again. We never saw what was responsible for the blockage. No wreckage, no obvious marks or debris on the pavement, nothing. I’m glad I live in a small city nowhere near California.
rtxn@lemmy.world 7 months ago
The Mythbusters did it! They couldn’t even get up to speed to begin the first experiment because the traffic jam formed naturally.
meliaesc@lemmy.world 7 months ago
Hm, this video isn’t available in my country.