[QUOTE=Cisco]
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.
[/QUOTE]
I’m not disputing that. But people are also entering the back of a rubbernecking jam faster than people at the head of it choose to exit. The reasons they don’t exit more quickly are different, but the impact is the same.
I used to drive on a long bridge, and when three cars started to almost pace each other, such that it was hard to get past, the same thing happened in a smaller scale.
[QUOTE=Voyager]
people are also entering the back of a rubbernecking jam faster than people at the head of it choose to exit. The reasons they don’t exit more quickly are different, but the impact is the same.
[/QUOTE]
That’s what you’re missing. People aren’t choosing to exit slowly, they just can’t accelerate as fast as the people entering the back can slow down.
[QUOTE=Trunk]
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?
[/QUOTE]
Almost every day I hear one of the traffic copters around here talking about a jam persisting long after the accident has been cleared. I don’t know if it moves - I haven’t ever heard them say it did.
As I mentioned, you can create a jam by turning on an informational sign, especially one with two screens worth of information. The standard ones seem to not be a problem.
I wonder what the half life of a jam is? It seems to be less than 2 hours but more than 15 minutes.
[QUOTE=Cisco]
That’s what you’re missing. People aren’t choosing to exit slowly, they just can’t accelerate as fast as the people entering the back can slow down.
[/QUOTE]
And how is the rubbernecking case different from the accident case? Anyone who has sit in a long line of cars stopped at a re light knows that different people react to the green at different rates. I don’t know if this is a choice or not, but I don’t think it matters.
Worth a read. It not only talks about (and models) the way the jams persist after the distraction clears, but it even talks about ways jams can be cleared out. I’ve actually experimented with it myself and, while the number of times I feel like I’ve actually had a significant positive impact on a jam is very small, the driving style it encourages is much more relaxing than the constant gas-brake-gas-brake cycle. Now when I’m in stop-and-go traffic, I try to settle at the correct speed so that even when the person in front of me is constantly stopping and going, I just cruise at a constant speed without hitting my brakes or wearing out my clutch. If you time it exactly right, the gap in front of you closes slowly and you’re juuust about to have to hit your brakes when the car in front of you lunges forward and stops again, leaving you a big gap to slowly close. Repeat while moving at as constant a speed as possible. Once you learn not to care whether or not people cut in front of you while you’re doing this, you begin to notice that not that many people do, and you reach enlightenment.
[QUOTE=Cisco]
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.
[/QUOTE]
How quickly cars join the back of the traffic jam has zero effect on how quickly the people at the front of the jam leave. To be clear, I am not arguing that a traffic jam is not self propagating. If cars join the back faster than they leave from the front, the jam will continue. My point is only that if there were nothing causing a hesitation in the lead drivers, the congestion would move backwards, clearing the area near the accident, the traffic jam moving backwards down the road like a pressure wave.
On review…
Thanks ntucker. I was looking for animation just like this, but could not find it.
The fact that the traffic does not clear at the accident scene, to me, shows that something is happening at this point to prevent people from accelerating away as quickly as they otherwise would. Something is acting as a barrier, creating traffic ‘pressure’ behind it.
[QUOTE=brazil84]
The only reasonable explanation for this is that “rubbernecking” helps to prolong the jam.
[/QUOTE]
No, it’s not. Even if you accept rubbernecking as a possible reasonable explanation, it’s not the only one. Others have been provided in this very thread.
[QUOTE=Cisco]
No, it’s not. Even if you accept rubbernecking as a possible reasonable explanation, it’s not the only one. Others have been provided in this very thread.
[/QUOTE]
I didn’t notice such explanations.
Here’s a question for anyone who cares to answer:
Besides rubbernecking, why is it that a distraction that is longer in duration might result in a traffic jam that is longer in duration?
(And you can assume for the sake of the question that whatever is causing the distraction is something that doesn’t otherwise interfere with traffic flow.)
[QUOTE=brazil84]
Here’s a question for anyone who cares to answer:
Besides rubbernecking, why is it that a distraction that is longer in duration might result in a traffic jam that is longer in duration?
(And you can assume for the sake of the question that whatever is causing the distraction is something that doesn’t otherwise interfere with traffic flow.)
[/QUOTE]
What, according to you, interferes with the traffic flow? Because it might be different for other people. Do you slow down or move over when people are walking or standing near the shoulder? Some do, some don’t. Distraction and obstruction aren’t concrete terms in this case.
[QUOTE=Cisco]
What, according to you, interferes with the traffic flow? Because it might be different for other people. Do you slow down or move over when people are walking or standing near the shoulder? Some do, some don’t. Distraction and obstruction aren’t concrete terms in this case.
[/QUOTE]
I do. And, has already been mentioned many times, if the guy in front of me slows down, I have to also, whether I would have or not if there were no cars ahead.
Even with no gaper block, I have seen a set of slower moving cars cause significant congestion behind them, and clear road ahead. Yes, the reason that the jam grows is that cars are arriving faster than leaving, but the reason for this is the slowness in front.
[QUOTE=Cisco]
What, according to you, interferes with the traffic flow? Because it might be different for other people. Do you slow down or move over when people are walking or standing near the shoulder? Some do, some don’t.
[/quote]
Depending on the situation, I might.
For the sake of argument, let’s look at a classic rubbernecking situation, where there is an accident on the opposite side of a highway with a nice wide divider in the middle. There are a couple banged up cars as well as an emergency vehicle or two.
Besides rubbernecking, why is it that a distraction that is longer in duration might result in a traffic jam that is longer in duration?
[QUOTE=Cisco]
The bottleneck occurs at the scene because people stop when the accident happens, either for safety reasons or to see if they can help.
[/QUOTE]
Oh, please. I don’t think anyone would deny that it’s sometimes necessary to slow down for safety reasons, but “to see if they can help”? Hah! That’s seldom the reason why motorists slow down at the scene of an accident – especially when it occurs on the other side of a dividing partition!
[QUOTE=Trunk]
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.
[/QUOTE]
There’s nothing involuntary about it.
[QUOTE=JThunder]
Oh, please. I don’t think anyone would deny that it’s sometimes necessary to slow down for safety reasons, but “to see if they can help”? Hah! That’s seldom the reason why motorists slow down at the scene of an accident – especially when it occurs on the other side of a dividing partition!
[/QUOTE]
What we need are severed bleeding heads to fly out at the gawkers… I think most folks would not even recognize the fact that they had side windows after that…
[QUOTE=Cisco]
:rolleyes: In some states it’s the law.
[/QUOTE]
Could you please cite the specifics of that law, please?
If find it extremely difficult to believe that people on the other side of a divided interstate, for example, are slowing down to determine if they can help, especially when there are plenty of other vehicles passing on the opposite lanes.
And even if that were the case, it’s still naive to think that this is the reason why people slow down at the scene of an accident. Human nature being what it is, it’s safe to say that they’re slowing down out of morbid curiosity. After all, how many of these people actually pull over to ask if they can help in any way?
In the instance that launched this thread, there were at least 5 emergency vehicles on the scene by the time I finally reached the front of the line. If I were required to stop, it would probably be to alert the authorities and do what I could for the victims. The help was already notified (their lights could be seen from quite a distance) and rendering aid. That didn’t have much impact on people resuming speed.
Sometimes I think people are just oblivious. When I’m in the supermarket, I see people who park their carts on one side of the aisle as they peruse the 87 brands of corn flakes, effectively blocking anybody who wants to pass from either side. Or for that matter, driving through a parking lot behind someone who has chosen to walk right down the middle of the aisle.
Traffic jams probably result in part from forgetting the rest of the world exists for awhile.