San Jose Mercury News: The man who invented metering lights: Roadshow


Editor’s Note: This story was reprinted with permission from the San Jose Mercury News.

Bay Area News Group

Q: Who is the idiot that invented metering lights? 
M. R. Pamidi
San Jose

A: Idiot? He’s Dolf May, a legend in the traffic world and one of my favorite interviews. Why are you so upset?

Q: I think they make traffic flow worse. I remember last year when the metering lights on northbound Highway 101 past the San Jose airport were off and traffic moved smoothly. When they are on, traffic backs up almost half a mile south. 
M. R. Pamidi
San Jose

A: Dolf was a traffic engineer in Illinois when he set up the first ramp meter in 1963 on the Eisenhower Expressway in Chicago. A traffic cop stood at an on-ramp with a hand-held light he would switch to red as cars approached. Dolf later became a professor at UC-Berkeley and moved to the Bay Area.

Studies prove ramp meters work. A Minnesota review in 2000 involved shutting off all 433 ramp meters in the Minneapolis-St. Paul area for eight weeks to test their effectiveness. When the meters were turned off freeway capacity decreased by 9 percent, travel times increased by 22 percent, freeway speeds dropped by 7 percent and crashes increased by a staggering 26 percent.

Closer to home, upset drivers pressed local officials to pressure Caltrans to speed up the meters on Highway 85 and the 25-mile drive from South San Jose to Mountain View. But travel time increased by 48 percent and drivers pleaded for the meters to be slowed down.

Metering lights have reduced travel time by 19 minutes on a 10-mile stretch of Highway 101 in San Mateo County. Travel speeds on 101 between Bernal Road and Capitol Expressway moved at an average of 36 mph before metering, and 44 mph after. There are now nearly 560 active ramp meters in the Bay Area and the goal is 1,320 by 2025.

Thanks to Dolf-the-Genius.