Issue 08
ATSAC
By Anne KeehnPhotos By Dan Monick
Illustration By Rich2
When Los Angeles city transportation engineer Gabriel Murillo was in high school, he thought that if he drove his car back and forth over the big, round sensors embedded in the roads, the traffic lights would change faster. After two decades developing L.A.’s traffic control system, Murillo knows this tactic doesn’t work. “It’s a myth,” he says. “It’s actually bad. At the point where the light would normally have gone yellow and given you green, it thinks you turned right. Now you have to wait longer.”
L.A. traffic is the worst in the country. Rush hour can stretch for over eight hours a day. According to the Texas Transportation Institute’s (TTI) 2005 Urban Mobility Study, the average peaktime traveler spent 93 excess hours sitting in congestion in 2003, and traffic jams cost each commuter about $1,600 per year in extra fuel and time lost. Yet, as costly and timeconsuming as L.A. traffic is, it could be worse. Much worse.
Four stories below downtown L.A.’s City Hall East lies the Automated Traffic Surveillance and Control (ATSAC) center. This large, windowless bunker-type room is the nerve center of L.A. traffic control. Seven giant screens stream live video footage of major intersections. Colorful charts and graphs light up PC monitors. Engineers are on call seven days a week to ease the flow of traffic on the streets above. According to TTI, traffic control systems like ATSAC collectively save L.A. residents over $1.5 billion a year in time and fuel.
Murillo sits behind his cubicle desk, and debunks two more traffic myths. Number one: Flashing your high beams does not make traffic signals turn green. Some ambulances, fire trucks, and police cars have special transponders that trigger green lights through sensors in the ground, and only they can make lights change at their convenience. Two: Left-turn lights do not always help the flow of traffic. “Everybody thinks a left-turn [light] will help them out,” says Murillo, “but it hurts everybody else. Imagine every signal cycle is a pie – if you have a left-turn, you have to take pie away from everyone else.”
Yet, last year, the L.A. City Council approved an $8 million plan to install 450 left-turn lights. “Politicians try to appease the public,” Murillo gripes. “There’s a lot going on behind the scenes that motorists don’t know about—that politicians don’t know about.”
The city established the first incarnation of its traffic control center before the 1984 Olympics, hiring a consultant to create a system that could manipulate the 118 traffic lights around the Los Angeles Coliseum. The ATSAC system was later created and designed completely in-house. Because of this, it is perhaps the most sophisticated and user-friendly traffic control system in the country.
The engineers who create and maintain all of ATSAC’s software are situated right across the street in the Advanced Transportation Systems and Research (ATSAR) center. Murillo, like the rest of the ATSAR staff, started in the ATSAC traffic control pit when he was hired by the Department of Transportation in 1989. “I always say our system was designed by traffic engineers, for traffic engineers.”
According to Murillo, the first system was expensive and awkward to maintain. “You needed these huge mainframe computers to run it. We needed to have annual maintenance contracts with some company that would come out and service the machines.” Worst of all, the system was not automated. Traffic lights had pre-programmed cycles that were able to ease traffic congestion for the first year, but quickly became obsolete.
Urban environments change constantly. Between 1990 and 2000, the population of the city of Los Angeles increased by about 200,000. This, combined with housing and business developments, continually altered the flow of traffic. “The problem with the old system was, eventually the predefined plans would be out-dated, and we had to go back and fix every light in the database,” Murillo says. “It was becoming a huge task just to maintain the signals. To go back there and ask, Is signal timing optimized for today’s conditions? Because every two or three years, traffic patterns are going to change.” Eventually, a decision had to be made: continue sinking money into a clunky, costly system, or take a chance and develop something that could be maintained in-house. Representatives from the traffic control center approached the Metropolitan Transit Authority (MTA)—the entity that funnels funds to them—and proposed a plan to create an automated traffic signal system that could adapt to the ever-changing environment on the streets.
There are approximately 4,300 traffic signals in L.A., about three quarters of which are on the ATSAC system. Sensors embedded in the road keep track of the rate of traffic. Lights at intersections then automatically tailor their cycle lengths to optimize traffic flow. The system relies on miles of cabling in the streets. Fiber-optic and copper wires stretch out across the city, carrying data from thousands of sensors. The streets have to be torn open to lay these cables down, a time-consuming and costly task. “The drawback to our [system] is it requires more infrastructure,” Murillo concedes. “Construction is very expensive.”
To keep the system running smoothly, an automatic troubleshooting system was developed, called the Arterial Incident Detection Algorithm (AIDA). Computers store 18 months of traffic signal history, “so we know what normal looks like,” Murillo says. “The sensors are the eyes and ears of the system.” If something happens to disrupt the normal flow of traffic, engineers are alerted almost instantly. If a traffic light is blown, AIDA is able to alert an engineer in three seconds. “Without this system, it would take a week to notice a defective light,” says Murillo.
He points to his computer screen. “Just today, in one of the areas where we turned on the adaptive system, an incident was detected. It might have been an accident. I just let the system handle it. The cycle length started going up, and traffic never backed up beyond what it normally would have.” If it wasn’t for AIDA, Murillo says, traffic “probably would have been backed up for two or three blocks. But with the automated system turned on, the congestion cleared up very quickly – within two cycles.”
As effective as the ATSAC center is, traffic jams remain an inescapable fact of life in L.A. According to Kartik Patel (opposite, right), an ATSAC transportation engineer, this is because there are simply too many cars on the road. “You can only push so much water through a pipe,” Patel analogizes. “If there are a ton of cars on the road, traffic is going to slow down.”
Another factor that contributes to congestion is the geographical layout of Los Angeles. Beverly Hills, West Hollywood, Culver City, and Santa Monica are cities that reside like islands within the expanse of L.A. They have their own jurisdictions, their own mayors, their own city halls—and their own traffic control methods.
Recently, an effort has been underway to allow all cities in Los Angeles County to exchange traffic data. “It’s really designed for viewing,” says Murillo, “not for control.” This information allows traffic control centers to see how their neighboring jurisdictions time their signal cycles. Culver City has opted to allow ATSAC to control their traffic signals, but Beverly Hills, West Hollywood, and Santa Monica choose to operate their own centers. Cross-town traffic is noticeably disrupted in areas that border these cities. Patel believes the other traffic control centers manipulate their traffic signal cycles to dump heavy traffic from their jurisdictions into his.
Because ATSAR is funded by the MTA, a countywide entity, all the software Murillo and his team develop is free to any agency in the county. “It surprises me that Beverly Hills doesn’t want our software when it’s free,” he says. “I always got the feeling they didn’t want to be controlled by L.A.; they always wanted to do their own thing.” Murillo compares Beverly Hills’ traffic control system to “little puppies that you have to give commands to individually.” He adds, “Our system is almost like a puppet master. Every cycle can be different. Theirs is not as efficient, because you have to go down there and manually program the timing for every cycle.”
L.A. and Beverly Hills coordinated their signals only once, in the wake of the 1994 Northridge earthquake. When the Interstate 10 Freeway collapsed, ATSAC decided to use Olympic and Pico as alternate routes. The traffic signals on the two boulevards were put on high cycles, in order to allow a steady flow of traffic. The problem was, Olympic ran straight through the middle of Beverly Hills. If the two cities didn’t cooperate, traffic would have been severely disrupted. “So I called Beverly Hills’ engineers and said, ‘This is our plan. Would you allow me to give you the timing parameters so we can coordinate our signals?’” Murillo recalls. “And they agreed. That was the only time.” Their cooperation was a success: The ATSAC center was awarded the 1994 Transportation Achievement Award in Operations by the Institute of Transportation Engineers for their response to the traffic crisis.
In May 2005, in reference to the activities of the ATSAC center, Patel told The Washington Post, “All this is happening, and most people don’t even know it’s happening. That’s the beauty of it.” ATSAC’s anonymity is perhaps a testament to its success. “People only start to ask questions when things go wrong,” Murillo says. Yet this anonymity has often hurt the traffic control center.
Many ATSAC employees continue to feel undervalued. In March 2005, engineers decided to protest what they deemed to be low wages by boycotting the L.A. Marathon, a traffic-disrupting event that typically requires engineers to work overtime. “It’s hard to keep good engineers,” Murillo says, “because they go to the Department of Water and Power. It pays more.”
According to Patel, back when County Supervisor Zev Yaroslavsky was an L.A. City Councilman he questioned the necessity of the ATSAC center. To test its effectiveness, Yaroslavsky attempted to have the system shut off for two weeks. After two days of the experiment, the city received so many complaints about horrendous traffic congestion that the ATSAC center resumed operations, and has operated continuously ever since.
Every day, on the surface streets of L.A., the worst traffic congestion in the country roars away. Four stories below ground, like invisible crossing guards, ATSAC engineers operate the most sophisticated traffic control center in America.