60 miles of the M1 each day for my commute, and so I ponder motorway congestion sometimes. Does anyone know what causes it?
I don't mean having 3 lanes of traffic nose to tail and doing 60mph, that's to be expected at peak times. I mean stationary traffic or 3 lanes doing 10mph for a mile or more.
Is it all down to the ripple effect of someone pulling into an overtaking lane and the guy behind having to brake? The one behind him has to brake harder as he hasn't seen it until a bit later etc etc until everyone's stopped?
Is it because of people dawdling in the middle lane and everyone has to go around them?
How can it be cured?
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Apart fom accidents and other incidents which can cause issues several miles back, the main reason is poor lane discipline, lack of space between cars and lorries overtaking each other at a speed difference of 0.1mph, causing the middle lane to block up at 56mph for three of four miles.
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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And in reply to truckersunite (who is bound to get in here soon) an overtaking manouevuer should be capable of being completed within a maximum of 30 seconds or 1/2 mile. Otherwise its not overtaking, it's sitting in the next lane for no purpose.
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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A lot of it is a ripple effect. All 3 lanes moving steadily, something happens to make people slow down or change lane or whatever. People behind have to slow a bit more and a bit more and finally someone at the back has to come to a stop. Then the problem clears and everybody moves off; as you drive along you can't see any accident or any obvious cause of the slow down/stoppage.
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Thanks, has there been any research into this? With all the motorway cameras, surely it must be possible to see the congestion and then look on the cameras ahead to see the cause?
Back to question 2, how can it be cured?
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MOst obvious is to keep vehicles further apart so that the ripple effect does not cause cars to come to a stop, but gently lift off the gas and then re-apply a few seconds later.
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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IIRC the purpose of the variable speed limits is to maximise the throughput of traffic by reducing the incidence of the ripple effect in high density traffic situations.
Somebody will have some pretty sophisticated mathmatical models of this, it would be interesting to find a website able to demonstrate the effect. It would lend itself to a impressive graphical display.
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pmh (was peter)
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I remember it was reported approx 10 years ago that a car braking sharply mid morning on the M25 anti clock wise just north of the M40 junction (by the viaduct) caused a ripple effect which was still measurable during the evening commute.
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If it was reported 10 years ago, it is probably still observable today! Butterflies and tornados come to mind.
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pmh (was peter)
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M1 Saturday south of Sheffield going north. The 60/40 countdown started.
RDS radio report told of an accident south bound.I guess the traffic control know people would lift off to look at the incident and have worked out the traffic flows better if it is deliberately slowed down first.
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I wasna fu but just had plenty.
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And in reply to truckersunite (who is bound to get in here soon) an overtaking manouevuer should be capable of being completed within a maximum of 30 seconds or 1/2 mile. Otherwise its not overtaking, it's sitting in the next lane for no purpose. -- Espada III
Not sure if this is relevant to the question - and surely it is the over-reaction (or under-reactions?) of the following car drivers that causes the ripple effect miles back? The original trucks are doing 56mph remember - give or take 0.1mph :o)
On a regular 40 mile commute down the M4 into London I think it was the car drivers that generally caused the stop-start chaos. It would often be the "fast" lane that stopped due to ripples, then the middle lane as drivers would dash over to make a few places, then of course the "slow" lane. I would often choose an unusual/memorable lorry as I joined the motorway, then see it sail past in the inner lane 40 miles later whilst I was playing the lane game with the other lemmings.
Following a lorry was much less stop/start and would not increase my journey time, though it could decrease it. I don't think that lorry drivers should be blamed for the shortcomings of car drivers.
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"Somebody will have some pretty sophisticated mathmatical models of this, it would be interesting to find a website able to demonstrate the effect. It would lend itself to a impressive graphical display"
How about this traffic jam simulator:
www.mtreiber.de/MicroApplet
This article is also worth a read:
www.amasci.com/amateur/traffic/traffic1.html
Ed.
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I know thais has been raised before but having just done the University run once again, I repeatedly saw the old problem of 2 lanes being blocked by lorries -- One wants to to 58MPH rather than 57MPH so it pulls out to overtake on a slight incline.
Unable to increase speed it just sits there forcing everything to try to funnel into the outside lane with the resulting build up and general slowdown of all traffic behind.
As said, I saw this practice time and time again with the icing being a coach trying to overtake in the 3rd lane so nothing could pass!
I am not saying this is the sole cause of congestion - far from it, and I do accept that lorry drivers have every right to do this -- I did think coaches & HGv's were not allowed in the outside lane of a 3 lane m'way but don't whether this is correct.
It would be easy to say that all HGV's & coaches should be restricted to lane 1 which I'm sure would allow for much less congestion. However, I acknowledge this is not practical and trucks and coaches have as much right to the road as cars.
Sorry lorry & coach drivers but is it really important to do that extra 1 or 2MPH? Perhaps it is and if so, so be it - you're bigger than us car drivers!
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It would be easy to say that all HGV's & coaches should be restricted to lane 1 which I'm sure would allow for much less congestion.
IIRC this situation arises in Holland, especially near the port areas, where trucks are limited to the inner lane only during peak hours. Still get congestion, and becomes very difficult to pull off at exits as all the trucks form a moving wall with very little space between each one. When the traffic is flowing the speed differential between the trucks and the outer lanes can become very large, and this adds to the problems of leaving/entering the flow.
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Wonderful simulator, thanks - hours of fun there! :-)
It's made me think of one problem - zipping. When the on-ramp is backed up and moving slowly. Only the front car should be "allowed" to join the carriageway. What we currently have is people jumping into flowing traffic from anything up to 10 or more places from the front of the join point (and often then tailgating so no-one else can get in, or forcing their way across lanes, but those are other issues). This results in mutiples stop/starts (or at least interruption to flow) where as one-by-one zipping would reduce this.
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>>How about this traffic jam simulator:www.mtreiber.de/MicroApplet This article is also worth a read: www.amasci.com/amateur/traffic/traffic1.html Ed.
Excellent, thanks!
If the motorway speed limit were to be 60mph for everyone (cars, trucks, buses, vehicles with trailers) should lots of these problems go away? Not many people do less than 60 so the speed differential should be easier to plan for, I suppose this is the idea of the temporary speed limits you see sometimes.
Interesting to see the simulation around the motorway entry ramp which wouldn't be fixed though.
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A jolly good read is "Critical mass, why one thing leads to another" which won a prize for science writing this year.
If you model mathematically the behaviour of drivers then once the traffic density gets above a certain level, jams just happen. They then migrate backwards (create one on your desk and have the front ones pull away when the jam is three or four cars long, while still adding them to the back, and you'll sell why) until you get to the front of them and can't see any reason for them being there.
V
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Having wasted some time with the simulator, I'm wondering if it's flawed, or whether there is an off-screen event! Reload it to defaults, set the ramp inflow at 0 vehciles per hour, maximise the time warp and watch. A jam *still* occurs, ahead of the ramp but then ripples back beyond the ramp.
Maybe it's what they call "sheer weight of traffic".
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I think you're right. Its the bend that does it.
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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Just had another look. Even with no vehicles on the on ramp, congestion is caused by trucks being slower than cars and in the outside lane.
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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