I'm pretty sure I heard a trail today for a programme on Radio 4 this evening at 9pm on the science behind traffic flows.
Might be interesting.
|
Yes 9pm - the blurb says.......
"Have you ever been on a motorway and the traffic grinds to a halt for no obvious reason? It's maddening when it happens, but if we could only see the wider picture, we might then realise that individual drivers are part of a larger mass that behaves according to complex physical laws.
Jonathan Edwards sets out to discover the physical laws that govern traffic flow."
|
There was a pretty good documentary on BBC TV about 10 years ago explaining the concepts behind these phantom traffic jams. They explained the theory behind maximum throughput of different road types, and what happens when you get close to or exceed these limits. I'm sure the radio prog will be interesting too.
Apparently, one main cause of thes jams is so-called 'brake light ripple', when drivers on a congested road brake progressively harder towards the tail of the stream causing an eventual stoppage. So the moral is dont drive too close and try not to ever brake unless you have to !
|
|
Using the brake to knock off the cruise control has been blamed IIRC - not sure I believe it. There are plenty of people who can't work out that following too closely and repeatedly having to dab the brake is a bad idea, cruise control users aside.
|
I frequently find that the person in front keeps dabbing their brakes because they are too close to the car in front, and that I can get away with just lifting my right foot slightly because I'm not quite so close.
--
L\'escargot.
|
|
I was taught both my instructor and my parents that using your brakes unless absolutely neceessary on the M/way was VERY BAD FORM. That was in the very early 80s. I'd interested to know from people who have been taught more recently whether this was part of your instructor's mantra.
|
using your brakes unless absolutely neceessary on the M/way was VERY BAD FORM. That was in the very early 80s. I'd interested to know from people who have been taught more recently whether this was part of your instructor's mantra.
Instructor: No, Parents: Yes. Test passed 1994.
Ed.
|
|
|
I was taught both my instructor and my parents that using your brakes unless absolutely neceessary on the M/way was VERY BAD FORM. That was in the very early 80s. I'd interested to know from people who have been taught more recently whether this was part of your instructor's mantra.
I STRONGLY disagree with this, and I spend a lot of my life in lane 3 of motorways.
If I see brake lights ahead then the first thing I do is show the guy behind my brake lights (without necessarily slowing down). I *especially* do this if the car behind is close - I really do not want to be rammed into the car in front of me if we do have to stop. If I do need to slow down then I'm already on the brake and I can stop as quickly as necessary.
What scares the hell out me, is being a passenger with someone who doesn't even start to slow down until he realises he's closing on the cars in front. If there's a biggish gap, the cars ahead could be almost stopped, and we're still doing 70MPH, and then need to do some serious braking. You just have to hope that the cars behind react in the same (or less) time too.
|
|
|
I was taught both my instructor and my parents that using your brakes unless absolutely neceessary on the M/way was VERY BAD FORM. That was in the very early 80s. I'd interested to know from people who have been taught more recently whether this was part of your instructor's mantra.
I passed my test in 1989 and was always told (cant remember who by, probably my Dad) to try not to brake and contribute to the ripple effect.
If I can see brake lights coming on 10 cars ahead I try and slow by engine braking to increase the gap in front and hopefully will not have to brake if the ripple reaches me.
|
|
|
|
|
"complex physical laws"
Indeed - it's a lot more complicated than you might imagine. I have a friend whose PhD thesis was on that very subject, as it applied to traffic flow in towns. His work seems to have passed over the heads of traffic planners everywhere, especially here on the Isle of Wight, where their solution to everything it to add more traffic lights - we have a large controlled roundabout that only functions properly when the lights stop working...
|
|
I remember one on the officers in the Traffic Cops TV programme discussing this very issue. His aim when driving on motorways was to always have a "window" around him such that if the car in front dabbed his brakes our man would simply have to lift off the gas a bit as described above by L'escargot thus avoiding contributing to the ripple effect. Since then I have always tried to follow this advice such that one of my hobbies (yes ok, i need to get out more.) is counting unnecessary braking instances by others (without being dangerous about it tho') ie he's braked 7 times to my one, wonder how much money I've saved on brake pads??? -
|
|
|
Traffic lights spring up like weeds.Their main purpose appears to stop the flow of traffic,they certainly do not help its flow.I think its another cunning plan to make life more difficult for the motorist to encourage other forms of transport.Bus lanes have the same effect.
--
rustbucket (the original)
|
|
I agree rustbucket. There is a new junction near mansfield on the A60 which has 48 traffic light posts of various types facing various direction. One used to just sail along there unhindered, now there is a long wait for no reason, everyone just sits there with virtually nothing moving in the other directions. And they put up big signs saying "Highways Agency - £millions improvement project for the community!". I think they must mean the lost-souls community of invisible ghosts every time this government says 'community'.
|
The science of traffic flows is NOT new iirc. it's all based on Queuing Theory and is a now well known and verified set of physical laws.
Put simply the traffic along a raod is limited by its width (no of lanes) , speed limits and the impact of slowing down and speeding up at junctions/turns/lights etc.
All highway engineering departments should be able to model traffic flows on a PC . Since many local councils in cities put into effect traffic measures that are impractical and have to be frequently revised, I suggest they don't bother or other things take priority.
Of course if the road is a UK motorway designed for 10,000 cars/hour and carrying 20,000 then the results don't need any theory to explain them!
madf
|
|
Does anybody know what IIRC stands for, please?
|
|
IIRC = If I Recall Correctly.
|
|
For those who missed it, open page www.bbc.co.uk/radio4/science/jonathanedwardslooks....l (non clickable on purpose to preserve HJ's bandwidth so cut and paste) and then press Listen again to Programme 1.
|
|
|
|
|
|
