Enforcement Key To 'Buffering' Flow Of Highway Traffic

By Robert Thomson
Sunday, October 26, 2008; Page C02

Dear Dr. Gridlock:

Ihave to laugh to keep from crying at the implementation of buffering concepts, either at the Woodrow Wilson Bridge or elsewhere.

I don't disagree that it works when it works, but historically it doesn't work, and it won't work as long as there are too many rats in the cage. If there were fewer rats -- interpret that as you will -- buffering devices wouldn't be needed!

A case in point: Virginia used to have traffic lights on the entrance ramps to Interstate 395 inside the Capital Beltway. I have not seen these operate in a couple of years, and when they did, they were ignored. To the extent that there is no effective enforcement of the variable speed lanes on the Wilson Bridge or thereabouts, the buffering concept fails.

John Binford

Silver Spring

I'm more optimistic than our letter writer about this concept of controlling highway traffic flow so that vehicles can be spaced out for safety. But he is right that it doesn't work if drivers are doing the enforcing.

Binford mentions two local examples. The older one is the ramp metering system in Virginia. By placing traffic signals on highway ramps, the Virginia Department of Transportation can slow the rate at which vehicles join the jam on the interstates. It's a theory that has been applied in urban areas for many decades and with some success.

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