FutureStructure

San Diego Smart Stoplights Reduce Traffic Congestion

Smart stoplight systems allow stoplights to memorize traffic patterns, communicate with each other and adjust the timing of green and red lights to improve traffic flow.

by David Garrick, The San Diego Union-Tribune / March 10, 2017
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(TNS) — San Diego is starting to have success reducing traffic congestion with smart stoplights, which have been installed in Point Loma, La Jolla, Mission Valley, Mira Mesa and Sorrento Valley.

The city’s largest installation of the lights, a series of 12 on Rosecrans Street from Hancock Street to Nimitz Boulevard, has shrunk travel time by as much as 25 percent and the number of times cars must come to a stop during rush hour by 53 percent.

“Everybody hates sitting in traffic so we’re turning to new technology to solve this age-old problem,” said Mayor Kevin Faulconer. “These smart signals adjust traffic lights to keep cars moving rather than sitting at stoplights.”

Smart stoplight systems, formally known as adaptive traffic signals, allow stoplights to memorize traffic patterns, communicate with each other and adjust the timing of green and red lights to improve traffic flow.

When one stoplight sees an unusually large volume of cars, it immediately relays that information to each stoplight downstream in the series. That allows those stoplights to stay green for longer than they usually would at that time of day.

Smart stoplights can also react to unpredictable events, such as patrons from a sold-out movie flowing from a theater after the show.

Using technology to boost traffic flow is much less expensive than widening roads or building transit lines, and those solutions typically face environmental hurdles and community backlash.

Nationally, only about 1 percent of traffic signals use this technology.

The city’s first use of them was a pilot project in 2014 on Sorrento Valley’s Lusk Boulevard that reduced congestion there.

In 2015, city officials created a $163 million, 10-year master plan to install modern stoplight timing systems and other advanced technologies that combat gridlock, including smart stoplights in several areas.

The city has now installed smart stoplights along heavily-trafficked Friars Road, La Jolla Parkway, Mira Mesa Boulevard and Vista Sorrento Parkway. And last fall, the city installed the Rosecrans Street smart stoplights with help from a $600,000 state grant.

Data from January shows the morning commute on southbound Rosecrans Street decreased from seven minutes to five minutes on average.

“The installation of these new adaptive traffic signals means less time spent on the road and more time for commuters to spend with their families,” said Councilwoman Lorie Zapf, whose district includes the area. “Residents are catching more green lights than ever before and the community is thrilled about it.”

Smart stoplights typically achieve less impressive results in exclusively commercial or residential areas, where relatively predictable traffic patterns make old-fashioned stoplight timing systems nearly as effective.

They are usually more effective in mixed-use areas where housing, commercial and industrial projects all come together, making traffic flow particularly irregular and unpredictable.

Because mixed-use neighborhoods with multi-story housing are the blueprint San Diego has chosen for future growth, officials say smart stoplights make sense for the city.

©2017 The San Diego Union-Tribune Distributed by Tribune Content Agency, LLC.