I’m not going to explain it all to you, because frankly I can’t off the top of my head - but you can do some Googling and find out. Basically cars are entering the back of the jam faster than they can exit the bottleneck. The bottleneck occurs at the scene because people stop when the accident happens, either for safety reasons or to see if they can help.
Your link disproves your argument, unless you think those Japanese guys are rubbernecking something.
In defense of rubbernecking…how are you supposed to explain why you are late to work if you don’t look? Your story is much more convincing with details like …“and the blue car was upside down on the Jersey barricade, and the whole front end of the red car was smooshed up”…
I take a quick peek so I know what to pray for. It’s practically the only time I offer up a prayer.
Slowing at an accident DOES have an effect.
I just believe that “rubbernecking”, that is, “turning to look at an accident” isn’t the cause. The cause of the jam is an INITIAL slow down caused by an involuntary reaction to the accident.
Traffic slows for a lot of reasons.
Traffic slows in the right hand lanes when the left hand lanes slow because people start moving into those lanes, and you have a capacity problem.
Traffic on highways slows on curves. Nothing to rubberneck.
Traffic slows because someone reacts too severely to the natural expanding and collapsing of gaps between cars travelling at 70 mph.
Traffic slows when there’s highway work, and they’ve put “jersey walls” in the breakdown lanes.
But, the notion that all these jams are cause by everyone in every lane going slow to look at an accident – while being accepted wisdom – just doesn’t stand up to scrutiny.
I’m not sure I understand the distinction you are trying to draw.
You don’t seem to dispute that an unusual sight can cause a traffic jam, even if all lanes are clear.
What you seem to be saying is that people who are stuck in the traffic jam will not affect the situation if they too look once they get to the front of an allready-existing traffic jam.
Is that right?
Yes, pretty much.
But, let me fill in the nuance on a couple things.
People, like FreddyThePig earlier seem to think that jams persist because of people not properly accelerating out of them. That’s what most people seem to mean when they rail against “rubberneckers”. I think that that is bascically a negligible factor.
As to an “unusual sight causing a traffic jam, even if all lanes are clear”. Yes, I believe that, too. But, again, I don’t ascribe it so much to “rubbernecking” as much as an involuntary respose to an emergency stimulus. Like I said, it also happens when lanes narrow, and when highways bend. It happens in places where the interstate goes up a hill, and people subconsciously slow down.
A great example is the changeable overhead signs. When there are messages on them, you will get minor jams up to the sign, and then free traffic afterwards. On heavy volume days, you can get major jams going back from the signs.
But, keep in mind that if you took the message off the sign, the jam would persist. It can not instantly free itself because they build from the rear. Sometimes, they won’t free themselves until volume drops when you get outside of rush hour.
It seems to me that one could test this as follows:
Create some distraction by the side of the road for 10 minutes during rush hour. Watch how long the jam lasts.
Create the same distraction by the side of the road for 20 minutes during rush hour. Watch how long the jam lasts.
If your theory is correct, the jams should be roughly equal in duration. Because it’s not the gawking of latecomers that causes the jam to persist, according to your theory.
Personally, I would predict that the second jam would last about 10 minutes longer. Once the distraction goes away, the jam starts to smooth out.
I’m not exactly sure what the difference is. A couple years ago, I was caught in a traffic jam that was caused by some coeds playing volleyball in extremely revealing clothing. Was that the result of an “involuntary response to an emergency stimulus?”
If not, I don’t see how a traffic jam caused by an electronic sign is any different. Or for that matter, a traffic jam caused by mangled cars on the other side of a highway.
Well, I don’t want to go back into what I wrote earlier, but what do you think would happen to a jam if the distraction was able to be magically disappeared in an instant?
It’s not. I’m really just responding to the argument that the OP is trying to make. . .that gawking AFTER the jam has started is the problem.
Jams happen. I’m just saying it’s a fallacy that “rubbernecking” – in the common parlance – is the contributing factor to their persistence.
Any thing that will make people slow can cause a traffic jam. One of the worst examples I know is on I-70 west of Denver. Heading east to Denver out of Idaho Springs there is a tunnel over the Interstate. The Tunnel is narrower than normal, but still fine to go through at 75. But just the perception of a skinny tunnel scares stupid people and the hit the brake a little bit.
It’s only a little problem, except on the last night of a three day weekend. But the tiny bit of slowing with the massively heavy traffic of people coming back from the mountains turns into a huge disaster. I -70 begins to slow, then stop, and finally to back up. Then the US-40 merge in gets backed up, and things get worse. You can have a 6 hour wait to get 10 miles, all because so stupid Californian got scared of a tunnel that’s a little skinny and slowed down. :mad:
Yes I have sat on that stretch of road many a time for hours, with no accident even to blame.
I already answered that question. Traffic would start to smooth out. Eventually the jam would be gone. And the sooner the distraction disappears, the sooner the jam will go away, all other things being equal.
Do you disagree?
It depends on road width and traffic levels, but it’s perfectly possible for a standing wave of traffic to form and persist with absolutely no obvious cause. It can even take just one person braking unexpectedly to kick off a wave, such that by the time someone a ways back reaches the front of the jam, there’s no indication whatsoever of what started it.
Check out this great video of a Japanese test track experiment showing the sort of waves you can get in otherwise unobstructed traffic. This article has some more informal discussion, and a nifty animation or two.
I don’t think this test will prove anything. As I stated back ('way back) in one of my posts, you only need one more idiot gawking and slowing down to stall all the people behind him again. Just one “latecomer” will do that – you don’t need all of them gawking to lengthen the jam.
That’s not true. If you look carefully you will see that the jam moves along the road in the opposite direction of the flow of traffic. If only the initial slowdown was caused by the accident, the jam would move backward down the road. You would be driving down the road, hit a triaffic jam, pass throught it, then several miles down the road you would pass an acccident at full speed. That doesn’t happen that way. The accident keeps the front of the jam in place while more cars pile up behind.
My husband was driving to work one beautiful summer morning and saw that a fender bender had occurred and people were pulled over to the side, in the parking lane. This was on a fairly wide city street.
What was notable about this accident was the cute blonde in the short red dress whose car was involved. Several things happened simultaneously:
What? 
Your post doesn’t make sense. You have not read the thread, have you? Specifically my post that you’re replying to and several posts by other people explaining this. Do some Googling or click some of the links that have been provided - they will help you understand, because right now you don’t understand.
That may be true, but it doesn’t necessarily contradict my point.
Which is that if the distraction disappears, traffic will start to smooth out and the jam will eventually go away (generally speaking).
This seems pretty obvious to me. I don’t see why people are having such a hard time accepting it.
I’ve read the thread, clicked the links and googled. I’m sorry if I have not made myself clear. In the video I linked, you can see that when someone slows down, cars start to back up behind him. The same thing happens when an accident first occurs. I agree, once this happens, a chain reaction has been started that is no longer dependant on the accident being there. A wave of slow traffic moves back from that point. The point I was hoping to show with the video is that the front of the traffic jam clears and moves backward. The pack of cars that were stopped get up to speed rather quickly. The congestion moves backward like a pressure wave through the moving cars.
Imagine a large pack of cars stopped at a stoplight. The first few cars start off, and within seconds, cars that were stopped mid pack are whizzing along at the speed limit. The pass the intersection at the speed limit. They do not creep along at 2mph and then accelerate when they get to the intersection. Clearly something is happening at an accident scene which is preventing the traffic from clearing as quickly as it should. If it is not the hesitation caused by drivers looking at the scene of an accident, I don’t know, and you have not shown, what it is.
I don’t think that anyone is claiming that all latecomers gawk or rubberneck. It seems to me it would take only a small percentage to prolong the jam.
I can’t figure out what you’re arguing about, but I think you guys should watch Koyaanisqatsi sometime. Lots of speeded-up footage of traffic. Looks like arteries flowing, it’s fascinating.
Personally I think the need to slow down and check it out (whatever “it” is) can’t be helped. It’s like going into shock for just a split second.
You’re missing a key difference between freeways and surface streets: the traffic coming into the back of the redlight line is limited by previous redlights.
The key word here, that you are apparently having a hard time accepting, is eventually. It could be hours.
I think I get the disconnect here, and it is forcing me to rethink a little.
In my example, brazil84 might be saying that if you magically made the jam disappear. . .he accepts that cars would still be moving in from the back, but the FRONT of the jam should move backwards, too, as cars accelerate out. And eventually, cars passing through the jam locations should be at full speed, like a red-light.This doesn’t actually happen when there is an accident, ergo rubbernecking.
The question for me is then. . .would the front of the jam move backwards if you magically made the jam?
I’m not sure. All these other situations I’m talking about (message board, corner, narrowing, someone mentioend tunnels) are stationary. It doesn’t take rubbernecking per se but some kind of slow-down stimulus.
More data required.
So, everyone join me in this:
they need to do my overhead-sign experiment to study jams. If what we’re saying about signs, and tunnels is true, then they need to put a hard to read message on it creating the jam, then remove the message, and see how the jam operates from that point forward.