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Gridlock Warrior — Ketan Savla is designing computational solutions to improve the flow of traffic in congested cities. “Smarter” stoplights may be just around the corner.
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It’s the peak of morning rush hour in Los Angeles, and USC Viterbi School of Engineering professor Ketan Savla is thinking about traffic. He’s stuck in the queue of cars headed north on Vermont Avenue waiting to cross the intersection at Exposition Boulevard. Traffic is so backed up that the line of idling vehicles extends south for about half a mile, all the way to Martin Luther King Jr. Boulevard.
As his Toyota Prius inches toward the stoplight, he’s frustrated — but imagining solutions. “If only the traffic lights at those intersections were timed [to be] consistent with traffic demand in different directions,” he muses.
Savla’s research is aimed at turning this daydream into reality. He’s developing novel ways to make traffic-control infrastructure like stoplights and freeway onramp meters more responsive to citywide traffic fluctuations, with an eye toward preventing these kinds of bottlenecks.
“I’m designing algorithms to improve efficiency,” says Savla, who is the John and Dorothy Shea Early Career Chair in Civil Engineering and Associate Professor of Civil and Environmental Engineering, Electrical and Computer Engineering, and Industrial and Systems Engineering. “I want to decrease the travel time that folks have when they commute.”
Easing traffic congestion is important to Savla because of the myriad ways it can benefit people (less road rage, more time for other pursuits) and the planet (fewer carbon emissions from tailpipes). Traffic efficiency “touches almost all aspects of our lives,” he says.
A cross-town conversation
“Smart” stoplights and freeway onramp meters are already in use in Los Angeles and many other cities across the country and the world. They employ cameras and magnetic sensors in the road to monitor the volume of cars in their immediate vicinities, and remote computers adjust green- and red-light times accordingly.
But these signals and meters typically don’t “talk” to one another about what’s going on blocks or miles away. “It’s a very myopic way of controlling traffic,” notes Savla — one he thinks can be smarter.
In a large metropolis like Los Angeles, which has upwards of 4,000 intersections and a dozen freeways, one traffic incident can cause slowdowns in multiple traffic streams. To make the roadways more resilient to disruption, “You need to look at what’s happening downstream and upstream,” he says. “You want to coordinate what you’re doing at all the intersections…because each has an impact on the other.”
Relaying information across such a sprawling network poses a complex computing task. That’s where Savla’s algorithms come in. These computations are designed to optimize the way a city’s computer software system handles the deluge of ever-changing data from traffic-control infrastructure and makes citywide decisions.
The following simulation illustrates the advantages of Savla’s “closed-loop” system, which changes traffic signal timings in response to real-time traffic, over an “open-loop” system, in which stoplights change at fixed times.