Coordinating the 19 traffic lights at the intersections around Devereaux and Algon Avenues in Oxford Circle depends on a tangle of 60-year-old technology that looks like rejected parts from the space program, pre-moon landing.
Of the city’s nearly 3,000 intersections with traffic signals, the lights in about two-thirds are antiquated and prone to breakdowns. They’re kept running with spare parts, ingenuity, and a crew of about a dozen workers who must set the lights’ timers by hand, or make repairs in one corridor of the city or another at least once a month.
“We have constant maintenance with those because they're older systems,” said Tom Schindler, traffic signal supervisor with the Philadelphia Streets Department. “Keeping the signals synchronized is a bigger thing than people realize.”
With congestion growing and the streets increasingly needing to be shared among cars, bicycles, and pedestrians, traffic light timing is a key tool to easing traffic jams. Except in rush hour, officials said, traffic signals’ timing can make the difference between a free flow of vehicles and congestion.
“It’s significant off rush hour,” said Patrick Callahan, traffic systems engineer with the city. “When volumes aren’t particularly high, that’s the deciding factor.”
»READ MORE: Why is Philly stuck in traffic?
Because of financial limitations and ongoing technical problems, though, Philadelphia’s 23-year effort to create a central traffic-control system has seen slow progress. It takes more than simply networking the city’s lights. The old traffic signals are incompatible with a modern control system, and the signals themselves need to be replaced. Only a third of the city’s signalized intersections have lights new enough to be networked through the Traffic Operations Center Streets Department’s offices on G Street in the Feltonville neighborhood, and of those, just 650 can be managed remotely. About 350 intersections are technically linked to the operations center but can’t be controlled remotely because of hardware problems.
To combat congestion, Philadelphia needs its traffic lights to be reliable and easy to adjust. Right now, most are neither.
Ideally, busy city corridors have what city officials call a green wave, a straightaway of green lights to allow a driver going a safe speed to travel for blocks without a red light. It’s safer and more environmentally friendly, since it requires less stopping and starting.
“This not only means more reliable travel time,” said Mike Carroll, the city’s deputy managing director for the Office of Transportation, Infrastructure, and Sustainability (OTIS), “but it provides central control over the speed of that movement so that vehicles have much less incentive to speed.”
But traffic signals inevitably drift out of sync. A brief power failure, or a minor mechanical problem, can cause drifts that over time that can significantly throw off the timing of lights on a corridor.
“When the progression goes off, people do call,” Callahan said. “They’ll notice they’re getting stuck at red lights.”
If the signals are closely spaced and mistimed, it can cause serious jams as cars stop in intersections.
It’s much easier to establish and maintain a green wave with networked traffic signals that can be controlled remotely. Lights can be timed without having to send people to their locations, and when malfunctions happen, traffic engineers are notified immediately, rather than waiting for irate drivers to phone in complaints.
On Callahan’s computer monitor is a map showing which signals are networked. Black dots indicate signals that aren’t integrated, and there are a lot of them. The Streets Department tries to link full corridors to the control system all at once at a pace of four corridors a year, but it can be expensive. The Streets Department has just $100,000 a year for traffic signal expenses, and upgrades rely on state grants. Recent projects include $2.8 million for 12 intersections on Castor Avenue, and $7.1 million for 24 intersections along Cheltenham Avenue.
Work to come includes a $9 million state grant for modernization on Oregon Avenue from Passyunk Avenue to Front Street, and on North Second Street from Callowhill Street to Lehigh Avenue.
Yet even when the city upgrades the technology at intersections, breakdowns continue to make the system far less effective than it could be.
The fiber optics that link the traffic signals to the central control system are vulnerable to small fires that can break out on the PECO power lines that run alongside them. A single fiber optic cable can be the lifeline that links an entire neighborhood in the city to the central control system, and when it burn outs, there are no backup connections. This is particularly a problem in Center City, officials said, where Philadelphia’s traffic problems are most acute.
“There’s not enough redundancy in Center City,” Callahan said. “It’s a problem with the fiber optic network.”
It’s costly and time consuming to replace the cables. In summer 2018, a PECO manhole fire on Juniper Street burned the fiber optic cables that allowed remote control of every traffic light in Center City between Market and South Streets, except for signals on Chestnut Street. Workers will have to dig up the street to get at the burned fiber optics. Those signals likely won’t be reconnected until the end of the year. In the meantime, the city has to go back to manually retiming them.
There’s no easy solution to the ongoing problem of PECO fires damaging the essential fiber optics, city officials said.
“Currently, we do not have a strategy to prevent such accidents,” said Rich Montanez, deputy commissioner of the Streets Department. “We continue to keep our eyes and ears on the telecommunications industry to see any new advances they make.”
In the meantime, city workers like electrical technician Ibrahim El-Hajmoussa keep busy repairing the innards of decades-old traffic signals. His workshop is piled high with the electro-mechanical devices’ parts and signal control boxes opened for maintenance.
The timing relies on dials and a complicated cam shaft that can be adjusted to set how long the lights show green, yellow, and red. The parts for these old machines aren’t made any more, so El-Hajmoussa has to be a scrapper as much as a repairman, devoting time to gathering used parts from other signals that can be recycled.