Friday, May 16, 2008

IN URBAN TRAFFIC, TIMING IS EVERYTHING

FRANK GREVE, MCCLATCHY NEWSPAPERS Fine-tuning controls on the nation's traffic signals would cut U.S. road congestion by as much as 10 percent, transportation experts estimate. It would also reduce air pollution from vehicles by as much as a fifth, cut accidents at intersections and save about five tanks of gas annually per household, according to the National Transportation Operations Coalition, an alliance of federal, state and local traffic departments and equipment-makers.

That's the good news. The bad news is that the average local traffic department earned an overall grade of D on the alliance's latest report card. Streamlining intersections is happening in only some cities and states, even though it's eminently doable. . .

Technologically, most U.S. traffic signals remain very 20th century, said Philip Tarnoff, director of the Center for Advanced Transportation Technology at the University of Maryland in College Park. Roadside or centralized timers drive most of them by changing lights at scripted intervals. . . If timers are accurate, and the prescribed signal intervals are based on accurate and recent traffic surveys, these systems can do as well as fancier ones in typical traffic situations.

That's a big if, however. Most timed systems aren't refreshed and adjusted at the three-year intervals recommended for busy intersections or ones that see big changes in traffic due to new homes or businesses. . . .

Lakewood, Colo., another community that closely tracked before-and-after conditions, found that synchronizing lights at just 16 of its intersections delivered huge benefits. They included a daily savings of 635 hours in driving time, 172 gallons of gas and 758 pounds of pollution emissions, according to Denver's regional traffic authority.

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