Going With Flow on Beltway
We've seen systems that control traffic flow through stop and go lights on ramps or through speed limits that change with the time of day. But the Variable Speed Limit program scheduled to begin tonight on the southeastern side of the Capital Beltway in Virginia is new and different.
Will it work? The key to success is whether drivers will obey signs telling them to slow down when the highway around them still looks relatively open. If they do, traffic should flow more smoothly through the work zone that reduces lanes around Telegraph Road. If they don't, it will be hurry-up- and-wait for years to come.
This letter is from a reader who noticed our Commuter page feature on Sunday about the new speed-control program and how such efforts succeed or fail.
Dear Dr. Gridlock:
I have long tried to adjust my driving speed to anticipate traffic flow fluctuations ahead of me. This creates buffering that minimizes brake and acceleration fluctuations for vehicles behind me. Fluctuations (modeled in physics as turbulent flow) are an important component causing traffic flow oscillations, as well as increasing gasoline consumption.
The downside is that there are too many drivers whose personal time is more important than that of other drivers. These people all too frequently speed up to cut into empty space between cars, and then need to brake hard, disrupting traffic flow. If more drivers were not so aggressive and creating flow turbulence, we would have reduced commuter times.
Monitored and appropriately reduced speed limits provide increased time buffering, another good approach that can be tuned to achieve benefits for commuters.
Most of you won't experience the Variable Speed Limit for a while, because the Wilson Bridge Project will begin by using it only at night, when traffic is lightest. But if you look at this link, you'll see what information will be provided to drivers about highway conditions. The information on traffic conditions and travel times will be available 24 hours a day, and could help you plan your trips.
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