Every traffic signal in the city -- all 4,300-plus of them -- is now part of the Automated Traffic Surveillance and Control System (ATSAC), an advanced network that allows engineers to communicate with and monitor traffic signals remotely. City officials say it will help reduce congestion and boost travel speeds.
Work on ATSAC began in preparation of the 1984 Olympics. Thirty years later, Los Angeles is the largest city in the country to have complete remote control over every single one of its traffic lights, according to the city's Department of Transportation (LA DOT). Mayor Antonio Villaraigosa pitched the system early in his first term as a crucial way to increase travel speeds without having to add lanes. He also said the technology will have a positive environmental impact, since it will reduce idling. With the implementation of ATSAC, the mayor's office says travel times in Los Angeles will be 12 percent less.
The system's completion -- after years of stop-and-go progress -- is credited in large part to Villaraigosa and the $150 million the city received after California voters approved Proposition 1B in 2006. Completing the endeavor required bringing about 1,100 unsynchronized intersections online and retrofitting another 1,200 with new technology. Edward Yu, a senior engineer who's worked for LA DOT nearly 20 years and oversees ATSAC, says its impact can't be understated. Traffic in some Los Angeles corridors, he says, "wouldn't be able to move ... if we didn't have the system online."
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Of course, Angelinos won't avoid congestion altogether, especially on freeways. But under the improved system, there's a variety of ways traffic can be controlled to run more efficiently on surface streets. For example, traffic signals are timed along corridors to increase the number of green lights. Sensors at intersections measure the volume of traffic going in each direction, and computer programs can respond by cycling the traffic signals in a way that minimizes gridlock. The entire system can be manually overridden -- from a central command center downtown -- allowing traffic officials to make changes and tweaks at a moment's notice to respond to construction, disasters, accidents and special events.Additionally, the same ATSAC system that runs traffic lights is also hooked up to the city's light rail and bus rapid transit networks. If a rapid transit bus is running late, for example, it can get an extended green light to help bring it back on schedule. Even the city's fire trucks are linked into the system, allowing them to get green lights on corridors as they travel to and from emergencies.
And it's not just vehicles taking advantage of ATSAC. Cyclists and pedestrians benefit too. One traffic signal pattern for intersections near schools is designed to allow extra time when students are arriving and leaving for the day. The ATSAC system even has "Sabbath timing" for crosswalks in communities with heavy concentrations of devout Jews. Since they refrain from using machines and electronics from Friday night to Saturday night, during those times the crosswalks are set to automatically trigger pedestrian crossings, eliminating the need to push a button in violation of Jewish law.
But most Angelinos won't always see the impact of ATSAC firsthand; it's more of a behind-the-scenes system. When a signal comes online with ATSAC, "a lot of times the Los Angeles driver doesn't really see anything right away," Yu says. "It's when the system goes awry that they'll feel it the most." Traffic engineers can make tweaks as problems arise throughout the city. The system is buttressed by about 400 closed-circuit cameras to help officials monitor trouble spots.
Historically, the only way to change traffic signal patterns would be for someone to drive to the intersection and manually reprogram it. Now, the ATSAC system allows engineers to alter individual traffic signal patterns remotely. The system's real genius, however, is that doing so is often unnecessary since it's automated. When there's congestion at one intersection, ATSAC knows how to change the signal timing elsewhere to deal with it. That means an army of traffic officials doesn't have to constantly monitor every single intersection.
ATSAC got a chance to test the system during the L.A. Marathon a few weeks ago. "What [we were] able to do is not only support the event with street closures but make the event better by manipulating the traffic signals around the event," Yu says.
The computer systems that run ATSAC were developed in-house and are maintained internally -- not by consultants. Los Angeles has made the software available to the federal government to share with other cities.
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