After years of development, Los Angeles reached a milestone that few other, if any, major cities can claim: Every single traffic light -- all 4,398 of them -- can be monitored and controlled remotely.
By Ryan Holeywell, August 2013
The city's transportation office is based inside 100 Main Street, the sleek new headquarters of the Caltrans regional office.
In the 2003 remake of the film The Italian Job, a gang of crooks decides to steal a safe full of gold while it’s being transported by armored truck through the streets of Los Angeles. But they face a hurdle: How can they plan the heist when they don’t know which route their target will take?“You gridlock every route except the one we choose,” Mark Wahlberg’s character tells his team. “Force the truck to go exactly where we want it to go.”
The plan goes off without a hitch. The team hacks into the Los Angeles Department of Transportation computer system and intentionally sets all the traffic lights to green in order to jam up the intersections, while simultaneously creating an opening that steers their target toward the spot where they want to strike. All the while, the city’s traffic engineers look on, hopelessly befuddled.
The real-life system featured in the movie is L.A.’s Automated Traffic Surveillance and Control system, or ATSAC. Edward Yu, the senior traffic engineer who oversees ATSAC, says he gets asked about The Italian Job constantly, and he always has the same reply. No way, he says, could Wahlberg and his team manipulate the city’s traffic lights the way they did in the movie. “It has a logic,” Yu says of the system, which is programmed to prevent conflicting green lights. “It wouldn’t allow you to do that.”
In reality, ATSAC is a much more sophisticated system than The Italian Job let on. This spring, after years of development, Los Angeles reached a milestone that few other, if any, major cities can claim: Every single traffic light -- all 4,398 of them -- can be monitored and controlled remotely. Today, ATSAC is quite possibly L.A.’s most powerful weapon in its ongoing war on traffic jams.
Housed in an underground bunker four floors below a city hall annex, a darkened room is illuminated by the glow of computer and video monitors providing a constantly changing view of traffic flow through the most congested city in America. It’s the culmination of a project that began 30 years ago when city officials, preparing for the 1984 Olympics, were faced with the task of keeping traffic moving around the site of the games without widening any streets.
What his team built -- a complex network that gave the city unprecedented control over 115 intersections surrounding the Los Angeles Memorial Coliseum -- was powerful for its day. For the first time, engineers could see what was happening at an intersection and make appropriate adjustments, often remotely, without having to leave headquarters. Under the old standard, if an intersection became congested, traffic engineers would likely only learn about it by getting an angry phone call. Then one of them would have to drive to the intersection to manually adjust the timing mechanism. The engineer would often get stuck in the very congestion he was trying to eliminate. Today, Rowe says, “we deal with [congestion] in a way we could never deal with it in the past.” Most important, ATSAC is no longer limited to the small area in which it began. It now blankets the entire city.
The improvements sputtered along for years, but former Mayor Antonio Villaraigosa, who was term-limited out of office last month, has been an advocate for ATSAC and made completion of it one of his early campaign promises. He ultimately delivered on that by negotiating with the state legislature to include $150 million for ATSAC in a 2006 state bond measure. “It was tough, [but] they also understood I was a big supporter of the transportation bond,” Villaraigosa says. “We needed to sell it to Angelinos, and that was one way to do it.”
Yu admits the amount of attention the technology gets from the city might be confusing to outsiders, since it addresses congestion on surface streets, not the freeways for which Los Angeles is infamous. “Everyone when they come to L.A. thinks ‘freeways, freeways, freeways,’ like it’s the hugest thing,” Yu says. “But there are more city streets we have to manage.” Indeed, within the city limits are 181 miles of freeway, compared to approximately 6,500 miles of surface streets, making ATSAC a crucial piece of the city’s fabric.
Most traffic signal systems, even relatively modern ones, use pre-programmed schedules that change based on the time of the day, working on the assumption that it’s easy to predict what peak traffic conditions will look like and when they’ll occur.
Adaptive signal control technology -- what Los Angeles is using -- adjusts signals based on real-time traffic conditions by tweaking things like the length of a green light or how frequently a cycle of signals rolls over. The first adaptive control systems were developed in the U.K. and Australia in the 1980s, and caught on here in the early 1990s.
There are several different well-known adaptive systems, with names like SCOOT, SCATS and RHODES. But while many major American cities use adaptive signal controls for some intersections, most still don’t. Compared to any of them, ATSAC is state-of-the-art. It’s likely the only adaptive control system that’s been developed in-house by a department of transportation (DOT), says Srinivasa Sunkari, a research engineer at the Texas A&M Transportation Institute who’s studied ATSAC.
“We maintain and operate it,” Yu says. “We’re not tied to the consultants. We had Oracle come in [and say], ‘We can’t do much more for you guys.’”
According to the Federal Highway Administration, outdated signal timing that fails to accurately reflect current conditions accounts for more than 10 percent of congestion and traffic delays on major road routes. A national report released last year by a group of transportation associations gave the nation’s traffic signals a D rating. That same report, however, highlighted Los Angeles as a city on the leading edge of traffic signal management. Federal transportation officials, who are on a campaign to encourage city and state DOTs to use adaptive signal timing, will likely point to Los Angeles as a model.
Already, the city of Long Beach and several jurisdictions surrounding it are converting over to the system Los Angeles created. Dave Roseman, Long Beach’s traffic engineer, says he was drawn to ATSAC because it’s more flexible than the existing adaptive control systems on the market. “Our vision was we wanted a system we could develop ourselves -- not a black box that we couldn’t tweak.”
The backbone of the system is the thousands of magnetic sensors embedded just a few inches beneath the surface of the road that provide information about traffic counts, speed and indications of just how congested a given roadway is. Known as loop detectors, they can be easily spotted as distinctive circles covered in tar on the surface of streets. While other systems provide updated data every five or 10 minutes, ATSAC’s data stream is ongoing. “We’re the only place I know of that gets real-time information,” Yu says. That data is, in turn, used to maximize the efficiency of the traffic signals. Traffic engineers provide basic instructions on how each intersection’s traffic signals should function, but ATSAC adjusts them based on constantly changing conditions.
The system can adjust to congestion coming from planned events (like a movie premiere) as well as unpredictable events (like a traffic accident). Still, Yu says, it sometimes requires the human touch. During police and fire situations, engineers can create a perimeter of red lights that extends beyond the official boundary set up by first responders. It’s also not uncommon for traffic officers on the ground at movie premieres and award shows to make a call to the traffic center and request an extended green light or two to get a Hollywood star to the event on time.
ATSAC isn’t just about helping cars (or stars). Some city buses are outfitted with transmitters that can assist them in avoiding congestion. For example, if a bus is scheduled to reach an intersection at 1 p.m. but doesn’t arrive until 1:05, the system can detect that it’s running behind and extend the length of the next green light to help it catch up. A similar pattern makes it easy to keep the light rail network on time as well.
The system also provides extended walk signals at times when a heavy pedestrian presence can be anticipated, like the end of the school day or the hours leading up to a game at the Staples Center. There’s even a “Sabbath time” schedule used at intersections in places with high concentrations of devout Jews -- who don’t use machines on Saturdays -- to ensure they’ll get a walk signal without having to push the button.
But how well does ATSAC really work? By its very nature, its performance isn’t something the average motorist will necessarily even notice, especially since it’s been in various stages of use for so long. But its advocates say it not only improves traffic flow and reduces delays, but also cuts emissions and prevents noisy trucks from lingering in neighborhoods.
On one of the corridors they studied, they found ATSAC increased average speeds by 13 percent during rush hour, and reduced delays caused by stopping as much as 43 percent. (There were even more dramatic results for the other corridor, but methodological factors might have artificially boosted them.) “It suits them very well, and it does something good for the motorists,” Sunkari, the Texas A&M researcher, says.
Next up for ATSAC, Yu says, will be figuring out how to take the huge volume of data it collects and use it to manage the demands placed on city streets. One way to do that would be to send instructions to drivers’ smartphones, alerting them to avoid certain routes and providing them with alternatives before they’ve arrived at a congested road. “Any removal of traffic, even 10 percent from certain thoroughfares, can have a dramatic effect on how traffic’s moving,” Yu says.
But for now, he’ll continue to fight the day-to-day battle against congestion, even though it’s often a thankless job in a place where there’s no shortage of complaints about lengthy drive times. “Every person is a traffic engineer,” Yu jokes. “But they only see one aspect of it.”