let me start by saying I’m not at all sure where this thread belongs, if a Mod wants to move it at some point, I’ll try not to weep.
The other day I was stuck in stop-start traffic on the motorway whilst driving to work, the radio traffic bulletin said that this was beacuse of an accident that had now been cleared to the hard shoulder, but there was still a traffic problem there because all of the drivers were were ‘rubbernecking’ on the way past.
I don’t think this was the case and in fact I don’t think that rubbernecking is all that common at all, here’s what I think it was:
[li]Accident happens[/li][li]Traffic behind accident has to stop[/li][li]Traffic behind stopped traffic also has to stop[/li][li]And so on[/li][li]Accident is cleared[/li][*}Traffic at front can go now, but…
[li]…Traffic behind can’t move until the front row has gone[/li][li]Meanwhile, new vehicles are still joining the statioanry queue[/li][li]This will persist until traffic thins out sufficiently to.[/li]
or
[li]Accident happens on opposite carriageway[/li][li]A few drivers slow down out of genuine surprise or caution[/li][li]The vehicles behind them have no choice but to brake at least as hard as the ones in front, but in relaity, they probably brake a little harder[/li][li]The vehicles behind that row have to do the same, braking a little harder[/li][li]Eventually, someone has to brake so hard that they stop[/li][*}A Stationary queue forms
[li]Since the queue can only disperse from the front, it looks like everybody wants to slow down to have a look at the accident.[/li]
This tends to be most noticeable when traffic is dense and fairly fast-moving, so any little blips in braking can’t be absorbed by the distance between cars (the traffic has less ‘compressibility’) - I’m thinking that traffic behaves a little like a fluid in these cases; the stop-start effect being analogous to something like ‘water-hammer’
I’ve heard of this before… possibly Cecil? A dog walks into fast-flowing but heavy traffic. A car slows from 40 to 30 to give the dog time to clear the lane. The second driver, not expecting this, slows to 28. And so on. An hour later, the dog is back home asleep, and there’s a traffic jam two miles long.
I’m wracking my brains trying to think of where I read / saw this, but the way traffic moves was “shown” (this is in “…” people, it does not say “proved”) to behave like fluid dynamics. It went on to say that to clear the backlog, cars should go off in waves and that speed limits before and after the accident can be used to regulate the flow of traffic.
However, to really minimise the effects we should all leave a good distance between us and the car in front (- yeah right, obviously this person never drove in rush hour traffic before) and not jump on the anchors too quickly when we see red lights in front, since that causes drivers too close behind to overcompensate and cause further knock-on effects as described above. Through a combination of slowing the rate at which the cars enter the “funnel” and by minimising the “oscillation” of those cars (brake-gas-brake-gas) through leaving a greater distance between each vehicle, the massive tailbacks can be avoided (and I would have been grateful for that earlier this week too).
The problem with leaving a decent gap between ourselves and the car in front is that traffic, behaving like a fluid under pressure, will flow in to occupy the empty space.
Absolutely. I’ve also found that if individual drivers take the pressure out of their driving (mine too), the traffic flows as slick as cat shit on lino.
I’m still thinking about where I saw this article, but it might have been on the TV. I’ll keep trying for you buddy. BTW, I’m London based and was caught in a stinker this week - have you heard of the M25? shudder
I have seen examples of actual traffic slowing due to rubbernecking (?) The entire speed went from 100 KPH to 40 and the reason people slowing to watch someone open their hood due to overheating. The car was well off to the side and there was no reason for anyone to slow. I watched as the drivers before me each took a turn to look at this and then sped up.
Maybe I’m misinterpreting what I saw, but traffic flowed normally almost immediately after I passed this car.
You may be misinterpreting it; once somebody has slowed down to take a look, everybody has to (for reasons outlined above) - but the people who slow down because they have no choice (they are just going through ‘the wave’) might be looking because they are wondering why the hell something so trivial has already slowed them down.
If you want a fluid dynamics reference, there is a discussion of traffic flow in terms of propogating waves in Linear and Nonlinear Waves, G.B. Whitham, Wiley-Interscience. Traffic is used as an example in many texts on waves, and this is just one example that I had handy. Good book if you’re into waves and/or math.
There are many interesting conclusions that can be found from studying traffic as waves. One important point is that overall flowrate increases at moderate speeds, but high speeds tend to reduce flowrate because the density (as measured by the inverse of inter-car spacing) tends to decrease as speed increases.
Yeah, I’ll agree that there’s a ripple effect behind but I’ve seen way too many examples of people travelling both ways relative to the accident slowing down to gawk. It’s the same reason why morons watch Jerry Springer or Jenny Jones; they want to see gore, sensationalism, other’s people’s misfortunes. If it’s obvious somebody has already stopped to offer assistance and I’m not going to scare the shit out of one of the unfortunate accident victims, I’ll blast my horn at any idiot in front of me stopping to gawk. They’re increasing the chance another accident will happen, directly responsible for delaying the commute of everybody behind them, and basicall displaying a real lack of class. I’m sorry but I have absolutely no tolerance for them.
No, I have to agree with what seems to be the sense of the original post – despite what everyone says about traffic slowdowns due to “rubbernecking”, the truth is that most people slow down because they have no choice, unless they want to plow through the car in front of them. It always annoys me to hear about traffic delays due to “rubbernecking”, because I seriously doubt that most of it is due to the kind of morbid and stupid curiousity that name implies (“Hey, look, an accident! Let’s stop and see if there’s anything good!”). It especially bothers me if it’s a jam I’m in, because I know that I’m not looking for this.
If there’s an accident on your side of the road with police hovering around you certainly WILL slow down because 1.) People always slow down when there’s a police car with flashing lights; 2.) You never know, with all those people walking around, when someone might step right in front of traffic.
I’ve never seen a case where I could clearly attribute the delay to real “rubbernecking”.
Oh really? You’ve never finally gotton past an accident and looked to the left to see traffic backing up as people travelling the opposite direction stopped to look? Please, friend, where do you live? I’m moving tomorrow.
the traffic backs up because once it’s started, people have no choice but to stop (it only takes one person to do the rubberneck thing, then everyone behind him has no choice) - after people have slowed down, it’s natural to wonder why, so then they look at the accident (or whatever cause)
