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The secret nerve centre under LA’s streets

About the author

Jack is the presenter of Science in Action on the BBC World Service. He trained as a mechanical engineer (with automotive and aeronautic design) before becoming a journalist. He has worked at the BBC for over a decade and has reported from areas as diverse as war zones and technology shows

The city of Los Angeles has a car-centric reputation, and deservedly so.

It can be an automobile aficionado’s paradise. Explore the more affluent areas and you will see high-end machinery being used as daily drivers. But the irony is that those supremely capable cars are likely mired in traffic.

A recent study indicated that commuters in LA spend around 60 hours per year in congestion.

To keep this city on rubber moving, Los Angeles has installed a computerised traffic overlord. The Automated Traffic Surveillance and Control (ATSAC) system links every single traffic light in the metropolitan area, and adjusts the timing based on input from thousands of sensors and cameras. The aim is to sync the traffic signals together, to limit congestion.

Less time spent waiting at a red light means a shorter commute, but also less pollution in an area that is famously prone to smog. Results seem to show the system is working, with the city’s Department of Transportation saying average travel speeds are up 16% from 1997 to 2013, and travel time down 12%. Emissions have also fallen 3% to 4%. If the system were turned off tomorrow, someone with a five-mile commute to work would see it jump from around 17 minutes to around 20.

The ATSAC nerve centre is deep underground, in a Cold War-style bunker with heavy metal doors. Most of the light comes from glowing flat-panel screens, which wrap around three walls. The desks in front of them are equipped with yet more screens. It resembles a NASA command centre, with graphic representations of traffic displayed on most of the monitors. Some wide-area maps show the familiar LA grid, overlayed with green, yellow or red information on traffic flow. Others offer extreme close-ups on junctions with circles flashing codes, representing some of the 18,000 sensors winking their data to the central control computer.

“Over 4,400 signals are connected via fibre optic and copper wire to this location,” says Edward Yu, an ATSAC engineer.

Yu is the man in charge, this centre is his baby, and how miserable the commute home tonight will be, for millions of drivers, is within his power to influence. He seems relaxed about the responsibility.

“This is all real time information, so we get second-by-second data from all these signals,” he says.

That data is used to adjust 4,398 traffic lights, to balance traffic flow. The system knows if traffic is building up in one direction, and can hold the green for those drivers a little longer, for example. Corridors can be set up through the city at morning and evening rush hour in opposite directions. Buses can be given priority, and lights can be held on red in every direction to allow emergency vehicles to safely cross.

One of the most important sources of data the ATSAC system receives is from loop detectors, which Los Angeles has buried into the road at major junctions. If you look closely at a picture of LA streets you might see the circular marks, a little over a metre in diameter, where roads have been cut and covered. The loops use electromagnetic induction to sense cars passing or sitting overhead. That is translated into information on traffic volume, speed and lane occupancy. But rather than using that information locally, to control just one junction, ASTAC receives the relay and makes appropriate adjustments from its centralised point of command.

“One of the unique things about our system is that it doesn’t look at just one individual traffic light, it looks at the network,” says Yu. “If it changes the timing at one location, it can change the timing for the whole network automatically.”

If this brings to mind the 2003 remake of the film The Italian Job, you would not be far wrong. In the movie, gold thieves make their escape in Mini Coopers, after manipulating the traffic lights in LA to bring regular traffic to a halt. But the city began installing the ATSAC system long before – in fact, shortly after the original 1969 film was made. ATSAC is decades in the making.

Although it has not been used in such a celluloid scenario, ATSAC does its part to help film stars; this is Hollywood after all. During the annual Academy Awards ceremony, the system is used to facilitate the smooth arrival and exit of the rich and famous. “We change the timing so that the limousines get in to the secure area on time,” says Yu.

So celebrities get a green light? “Absolutely,” he says. “At certain signals we will adjust the light so that the celebrities or people coming to the show get priority over regular traffic.”

The aim is for us all to benefit, though, and other cities are looking at either implementing Los Angeles’ system or a similar one. Currently the traffic information is used in-house, but in the future the plan is to make it available to the likes of Google or the traffic app Waze, so that motorists can access it as well. Were that to happen, Angelenos might be faced with a more welcome challenge: deciding how to spend the extra minutes they gain.

(Photo: Quincy Dein/Getty)