Merging in Turn
Discussion
As a number of people have already mentioned, the filtering is supposed to reduce the rippling effect. The only way that rippling can be avoided (or more likely reduced) is by the closed lane matching the speed of the open lane. If you have already reached the bollards then your speed will be considerablly slower than the other lane (ie stopped!). When you pull in, it causes the open lane traffic to slow (to allow for your acceleration) and then causes rippling. If you pull in before the 100 yards, then you can match your speed and no one is delayed by more than needed.
Munta said:Excellently put!
As a number of people have already mentioned, the filtering is supposed to reduce the rippling effect. The only way that rippling can be avoided (or more likely reduced) is by the closed lane matching the speed of the open lane. If you have already reached the bollards then your speed will be considerablly slower than the other lane (ie stopped!). When you pull in, it causes the open lane traffic to slow (to allow for your acceleration) and then causes rippling. If you pull in before the 100 yards, then you can match your speed and no one is delayed by more than needed.
vladd said:
Why are you stopped when you reach the bollards? Generally if you're in the right lane, merging into the left, you're travelling faster than the left lane, not slower? I don't get what you're trying to say.
Because normally you slow down as you approach an obstruction or hazard. The closer you are to a hazzard, the slower you are so as you are almost at the bollards, you would stop.
The point being that at 100yrds or so, your speed is more likely to be the same as the traffic on the left. As you pass that point, you will naturally slow down. By the way, if you left it late to break heavyly in the closing lane, then you would cause rippling in that lane causing congestion many miles further back.
Some may say that if the traffic in the left lane is nearly stationary then it is ok to leave it til the last minute. The problem here is that the traffic is nearly always stationary due to the ripple effect having taken place earlier as proven when the traffic is flowing normally through the contaflow.
The other thing with closing lanes is that all traffic slows as the obstruction approaches. At 200yrs traffic may be moving at 50mph with 7 car length gaps between. at 100yrs trafic is at 30mph with 4 car gaps. At 50yrds, 20mph with 1 car gap. If you tried to pull in at 50yrs then you would force others to brake hard. At 100yrds the drivers could accomodate you, often without braking and therefore the ripple doesn't start.
Edited to add these references
<a href="http://www.theatlantic.com/issues/2000/12/budiansky.htm">www.theatlantic.com/issues/2000/12/budiansky.htm</a>
<a href="http://gauntlet.ucalgary.ca/story/2141">http://gauntlet.ucalgary.ca/story/2141</a>
This link has an excellent simulation of traffic patterns - give it a go!
<a href="http://ccl.northwestern.edu/netlogo/models/TrafficBasic">http://ccl.northwestern.edu/netlogo/models/TrafficBasic</a>
And an even better one that shows the effect of merging traffic - select SPURSPERRUNG and play with the controls
http://vwisb7.vkw.tu-dresden.de/~treiber/MicroApplet/index.html
>> Edited by Munta on Friday 14th November 14:19
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