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PostPosted: Thu Aug 05, 2004 18:52 
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I found an intriguing article on traffic flow here:
http://www.amasci.com/amateur/traffic/trafexp.html

Whilst the author doesn't make out that this is 100% correct, he does have some very good points. Perhaps if drivers were taught theory like this, we could reduce congestion on all types of road.


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PostPosted: Thu Aug 05, 2004 20:05 
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Makes a great deal of sense, but, wouldn't the polli's make this sort of driving illegal, wouldn't it remove the need for congestion charging.

Heavens above, we can't have this sort of subversive driving behaviour, don't we realise we are the great satanic cash cows for our beloved leaders, how, if we were to adopt this sort of driving style, would the polli's trouser our hard earned cash?

Anybody proposing this sort of safe driving must be studied, for perhaps, all of ten seconds then legislate against it.

Having said all that, I believe this should be looked at in greater depth by people better qualified than me, then put forward for serious consideration.

Well done that man. 8-)

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PostPosted: Thu Aug 05, 2004 20:22 
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If you drive in heavy highway traffic, you've probably seen a traffic wave develop at a construction site where one lane is blocked. You crawl and crawl at 3 mph until you get to the bottleneck, then you take your turn merging as the two lanes sloooooooowly come together. Then you race off at 60 mph! The merging lanes formed a terrible bottleneck, yet the open lanes ahead were not a bottlneck. A "traffic wave" develops at (and behind) the merge zone. After the bottleneck, it's clear sailing.


I saw this when they were resurfacing parts of the M6 late one night. It took us ages to get to the one lane restriction and you could accelerate back up to normal speed as soon as you got into the single lane section.

The only caveat to this is when the congestion is really heavy, when I think even this clever solution may not work.


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PostPosted: Thu Aug 05, 2004 21:07 
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Well I actually figured this out for myself some time ago, and to a certain extent found that it works. In fact its blindingly obvious and I find it amazing that other drivers are either too stupid or impatient to figure out that if you see a queue of traffic ahead there is no point at all in charging up behind it, hoping it will vanish in front of their eyes, then braking like crazy when they realise they are going to have to stop. Did I say "when you see", tut silly me, that mean looking beyond the car you are tailgating ahead, getting your thumb out of your arse and engaging your brain doesn't it?
You can actually watch their lack of thought and forward vision bringing their lanes to a halt as you cruise slowly by, and sometimes you can keep going whilst they are braking, moving, braking, wash rinse and repeat.
Of course you always get the terminally impatient lane jumpers who try to take advantage of the space you've created by rushing off down it (without giving a seconds thought as to why they may just be a little space there in the first place) but at least you can try. And as the guy in the States says, look behind and you'll see your lane still moving as well.

Sorry, that was a rant, but I just wish people would just damned well think once in a while.


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PostPosted: Sat Aug 21, 2004 09:54 
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The person is a complete nutter :!:

To think you can more through any congestion at 35mph.

Our congetsion speeds range from 0 to 70 mph, making their point rubbish.

Reality calling :P

You leave a gap on the M25 and it will be filled inside of a 60 sec time span.

Conjestion is simply just that, it cannot be avaded :!:

Simply by holding back, you reduce the traffic flow behind you, which may not be apparant in your rear view. But somewhere down the line you have caused just another bottleneck :twisted:

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PostPosted: Sat Aug 21, 2004 11:33 
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Why should you worry? You're a biker and push straight to the front, anyway! :D


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PostPosted: Sat Aug 21, 2004 19:57 
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bmwk12 wrote:
The person is a complete nutter :!:

To think you can more through any congestion at 35mph.

Our congetsion speeds range from 0 to 70 mph, making their point rubbish.

Reality calling :P

You leave a gap on the M25 and it will be filled inside of a 60 sec time span.

Conjestion is simply just that, it cannot be avaded :!:

Simply by holding back, you reduce the traffic flow behind you, which may not be apparant in your rear view. But somewhere down the line you have caused just another bottleneck :twisted:


Actually, it does it work. Its the anal way the British think that means it is difficult to put into practice.


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PostPosted: Sun Aug 22, 2004 11:35 
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Its not rubbish at all. There was a program on TV a while ago, surveying traffic flow on the M25. One thing they could show very clearly was the start of one of these - all it needed was the usual close driving in the outside lane, one car applies brakes, and from the bridge they were filming from you could clearly see the effect travelling backwards as each driver was forced to brake earlier than the one in front, all bunched up and slowed down.


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PostPosted: Sun Aug 22, 2004 13:18 
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VSL on the M25 reduces these stop start jams. you still get them but the changes of speed are ironed out a bit. driving at a fairly constant speed is much easier than stopping and starting all the time.

Simon


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PostPosted: Sun Aug 22, 2004 15:01 
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simon h wrote:
VSL on the M25 reduces these stop start jams. you still get them but the changes of speed are ironed out a bit. driving at a fairly constant speed is much easier than stopping and starting all the time.

Yes, and on busy motorways (where unimpeded progress at the speed limit is not possible in any lane) the best way to maintain traffic flow is:

1. Keep a constant speed
2. Maintain a 2-second gap
3. Minimise lane-changing

Which rather goes against the conventional "keep left" advice.

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PostPosted: Wed Aug 25, 2004 17:07 
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ar wrote:
I found an intriguing article on traffic flow here:
http://www.amasci.com/amateur/traffic/trafexp.html


This bloke has got it nailed. I figured this stuff out for myself ages ago, but
he has it spot on. The greedy 'me first' driving culture makes the motorways work like a slinky spring, with bottlenecks slowly migrating along in waves. Yes, that's the effect. That is why I like driving in LA (when the traffic moves all!). All the lanes have equal priority, so people drive in the slow, middle and fast lanes and everybody gets where they are going at the same rate. Recently, a chump from the RAC foundation has been prattling on about lane discipline as if he knows best. The trouble is, everybody want to be in the fast lane or the middle lane, so the slow lane is empty. Why is that a surprise?

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PostPosted: Wed Aug 25, 2004 17:49 
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PeterE wrote:
Yes, and on busy motorways (where unimpeded progress at the speed limit is not possible in any lane) the best way to maintain traffic flow is:

1. Keep a constant speed
2. Maintain a 2-second gap
3. Minimise lane-changing

Which rather goes against the conventional "keep left" advice.


I don't think it goes against it - maybe qualifies it. If a variable speed limit is in force then there is (or should be), by definition, a degree of congestion and there will be little or no speed differential between the lanes. So changing lanes serves no purpose. Nevertheless, if the gap in the lane to the left is sufficiently large to allow the minimum (2 seconds) separation from vehicles ahead and behind, then returning to the left remains, in my opinion, the correct action.


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PostPosted: Wed Aug 25, 2004 18:06 
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basingwerk wrote:
This bloke has got it nailed. I figured this stuff out for myself ages ago, but
he has it spot on.


Congratulations, basingberk. You really do know it all - NOT.

basingberk wrote:
The trouble is, everybody want to be in the fast lane or the middle lane, so the slow lane is empty.


QED


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PostPosted: Wed Aug 25, 2004 18:15 
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though i didn't drive myself in LA i did note that traffic didn't stop-start as much, nor were people weaving about. the biggest lane disapline problem was the "Californian shuffle" which consists of moving across most, if not all the traffic lanes in one go, either upon entry or when exiting. partly to blame is the large number of exits, and the gaps between them and the (legal) HOV exits (literally just before the junction-my mum took the HOV exit before ours to make sure she had plenty of time to move over). The only other problem mum had was not being able to see well till we got the giant SUV-higher driving position made her visiblity much better.

Traffic speeds were maybe 10-20 mph below the limit when traffic was heavy, but moving, and was pretty constant. of course round by LAX was jammed, but that's those tourists :roll: (actually it's trying to fit about 5 junctions in three miles, with lane drops and 5 main running lanes (about two lanes under capacity for the straight through traffic), bit like Heathrow will be when the works are done-why they didn't build c/d lanes at heathrow i have no idea-cost doesn't matter when the other option is a dangerous layout surely?)

Simon


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PostPosted: Wed Aug 25, 2004 18:32 
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Observer wrote:
PeterE wrote:
Yes, and on busy motorways (where unimpeded progress at the speed limit is not possible in any lane) the best way to maintain traffic flow is:

1. Keep a constant speed
2. Maintain a 2-second gap
3. Minimise lane-changing

Which rather goes against the conventional "keep left" advice.

I don't think it goes against it - maybe qualifies it. If a variable speed limit is in force then there is (or should be), by definition, a degree of congestion and there will be little or no speed differential between the lanes. So changing lanes serves no purpose. Nevertheless, if the gap in the lane to the left is sufficiently large to allow the minimum (2 seconds) separation from vehicles ahead and behind, then returning to the left remains, in my opinion, the correct action.

But in these congested conditions, what you often see is people diving into any reasonable gap that opens up (whether to left or right) in the hope of making better progress. This certainly doesn't improve overall traffic flow and if it causes any kind of ripple effect is likely to make it worse.

There is also an argument on motorways with frequent junctions such as the M60 that it makes sense to leave more space in Lane 1 for people joining or leaving the motorway.

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PostPosted: Wed Sep 22, 2004 12:57 
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I have noticed this effect too. I have only held a licence for 9 months, but do a lot of Mway driving, particularly M27 - M3 interchange. You can almost guarantee a brake wave at the M271 - M27 junction Westbound and why does thius occur? Volume of traffic is one reason, but its the people that trickle down the slip road at 40mph then try and push out into the traffic before picking up speed! I always aim for 70mph on the slip road and then speed match with the car i want to join behind. This means I dont slow anybody down on the main carriageway and dont back traffic up the sliproad which magnifies the slow joining traffic problem.
If one of these waves does occur, surely a rolling roadblock started about 3-5 miles before would neutralise the wave and so improve flow and capacity.

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PostPosted: Wed Sep 22, 2004 13:29 
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Pug205GRD wrote:
I have noticed this effect too. I have only held a licence for 9 months, but do a lot of Mway driving, particularly M27 - M3 interchange. You can almost guarantee a brake wave at the M271 - M27 junction Westbound and why does thius occur?


Its the end-effect of a mass exercise in game theory. Basically, all of the players (drivers) want to win (get home/work first), so they drive with that single goal in mind, and bugger the opposition (other road users). A better way to play the game would be not to charge forwards at the first sign of a break in the jam, but to show a little patience and chill out. Unfortunately, on our greedy and self obsessed little island, those days are gone, and we are left with a ME first generation of tailgaters, speeders and all manner of other impatient toe-rags.

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PostPosted: Wed Sep 22, 2004 15:28 
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We all know that basingwerk, but it only takes a few people to understand the way these things happen and to know how to counteract them. If these people can be bothered to act on what seems a good thing then we all benefit and the ME generation gets home that bit quicker/easier without even noticing! Im prepared to drive in lane 2 and hold traffic at a reasonable pace if it helps overall traffic flow. Indeed I have done this on a 10 mile length of M27 between M271 and Bursledon (J8?). All those in front of me were stop-starting the whole time, I was in 3rd gear, feet off all the pedals at about 15mph and I didnt stop once and didnt have a massive gap in front of me either. All those in lane 2 following were moving more or less at my pace whereas the other 2 lanes were yo-yoing back and forward.
Why hasnt the highways agency tried experimenting with putting a rolling roadblock into a motorway about 3-5 miles before a brake wave. Im sure they could figure out quite quickly the opimum speed, distance etc. it would take to neutralise the wave. It could even be done on environmental grounds because a car is at its most inefficient when it has stopped. If it is going it is more efficient and most people will choose to stick in the highest gear they can when driving slowly. I can get away with 5th gear at just 20mph, but then I do drive a diesel.

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PostPosted: Wed Sep 22, 2004 18:25 
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basingwerk wrote:
Unfortunately, on our greedy and self obsessed little island, those days are gone, and we are left with a ME first generation of tailgaters, speeders and all manner of other impatient toe-rags.


Yeah well, I've made this (and/or similar points) in other threads but each time it's given a damned good ignoring. Most folks seem to find it easier to grab hold of a small issue and extrapolate it or nitpick it to death rather than face the fact that British society is precesiely as you paint it.


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PostPosted: Tue Sep 28, 2004 14:27 
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Rigpig wrote:
basingwerk wrote:
Unfortunately, on our greedy and self obsessed little island, those days are gone, and we are left with a ME first generation of tailgaters, speeders and all manner of other impatient toe-rags.


Yeah well, I've made this (and/or similar points) in other threads but each time it's given a damned good ignoring. Most folks seem to find it easier to grab hold of a small issue and extrapolate it or nitpick it to death rather than face the fact that British society is precesiely as you paint it.

You and basingwerk are probably right that there's much less patience and courtesy than there used to be. If it's not tailgating then it's the rush to beat other shoppers to the empty checkout in Tescos (I'll hold my hands up here, I am sometimes guilty of that one). I'm not sure what the solution is, though. Do we take the approach that this is how people are now so how do we change the people, or that this is how people are now so how do we manage the situation? And how do we best apply that to the roads?

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