As a student at the University of Pennsylvania in the late 1990s, Jerilyn Dressler and her friends used to go shopping on South Street and share a cab back to West Philadelphia.

The cabdrivers had the traffic lights figured out so a "succession of greens" lit their way. Driving from one corner of the city to another was much easier than it is today, she said.

"You could get through a number of lights" without being stuck at a red one, said Dressler, an accountant who works in Center City and lives in Fairmount. "But now you can get through two."

Dressler, 39, asked the Inquirer and Daily News about traffic lights through Curious Philly, a platform for readers to ask questions about how the city and the region work.

She wrote: I wonder about traffic lights! How is their programming determined? Why are some lights seemingly red forever? Why aren't they timed to get you through many blocks faster? They also seem to break a lot at major intersections. What is the process and timeline for repair?

If it seems to you, like Dressler, that you never catch three greens in a row, especially in certain sections of the city or the region, it's not your imagination. And if it seems that in some places red lights are longer — and green lights shorter — than in others, chances are excellent they are.

Here's one reason: With 2,560 municipalities, Pennsylvania is a national leader in its number of local governments, and unlike in New Jersey and other states, every single town owns and maintains the traffic signals within its borders.

And there are other reasons that aren't hard to see: population growth, ride-sharing, construction, even safety. Slowing drivers down, goes the argument, might save lives.

Traffic-engineering experts say municipalities should adjust the timing of lights every couple of years. Philadelphia, on the other hand, aims for citywide re-timings in a five-year cycle as well as by resident request at individual intersections.

But, traffic gurus pledge, help is on the way. Philadelphia is in the middle of a citywide traffic assessment, and is thinking about switching to the software that California uses to help manage its notoriously crowded roadways. And PennDot is considering taking control of 160 lights at or near access to I-76 to better coordinate the flow of traffic fleeing the Schuylkill Expressway.

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State transportation officials also are giving money to local governments to fix traffic-light timing problems that plague many of them.

On Monday, PennDot will begin accepting applications for its fifth round of annual grants to municipalities trying to make their traffic signals more efficient and to address a common complaint at municipal meetings: traffic congestion.

PennDot has distributed nearly $80 million through the grant program, called Green Light – Go, for projects such as installing traffic volume detection cameras and LED bulbs (which use less energy and last longer), and, sometimes, removing unnecessary traffic lights.

PennDot has given Philadelphia more than $20 million through the program for projects such as installing traffic controllers along Second Street and modernizing signals along Castor and Cheltenham Avenues.

By necessity, every municipality has to approach traffic issues differently. And money isn't the only solution; coordination is also key.

"It's a real challenge in places like Pennsylvania that have so many jurisdictions involved in signal control," said Thomas Jacobs, director of the Center for Advanced Transportation Technology at the University of Maryland. "If you have a corridor with multiple municipalities and, say, five of the six participate [in the grant program] and upgrade their signals and one doesn't, you have to encourage them to do the same and take advantage of the program or you have a bottleneck."

Several municipal officials in the region cited the PennDot grants —  which require a 20 percent municipal match — as the reason they are able to upgrade their traffic signals now, instead of waiting to scrape together the funds.

In New Jersey, the owner of a roadway — whether the state, a county, or a municipality — is responsible for traffic signals on that road.

Like other municipalities, Philadelphia uses national standards for determining how long green, yellow, and red lights should last based on factors such as speed limits, intersection crossing distances, road conditions, and whether vehicles are traveling uphill or downhill. City officials enter vehicle and pedestrian data into its software, which tells them how long lights should be red, yellow, or green.

The city started switching from electromechanical to computerized traffic signals in 1994, said Richard Montanez, deputy commissioner of transportation for the city's Streets Department. About half of the city's nearly 3,000 signalized intersections are now computerized, which allows for better coordination.

In a perfect world, Montanez said, every motorist would drive at or just below the speed limit. The city aims to time lights so that they would change to green as these drivers approach an intersection. But that doesn't account for drivers' varying speeds and pedestrians in or crossing the road. Then there's the axiom that one driver's green light is another driver's red light.

Philadelphia is installing pedestrian signals on Market Street.
Michaelle Bond / STAFF
Philadelphia is installing pedestrian signals on Market Street.

In Center City, because traffic volume tends to be about equal in various directions, traffic lights tend to be red about half the time and green the other half at most intersections. Where a driver is in the city determines the length of time necessary to wait at a light.

But as conditions change, the city is "constantly" reassessing and making adjustments, Montanez said.

More people means both more drivers and more pedestrians. Drivers have to yield to them when making turns, which can clog streets. So can stopped delivery trucks, circling Uber and Lyft drivers, and encroaching construction equipment.

"We are timing the city for everybody to utilize the city," Montanez said. "It's not just the motor vehicle. It's for all modes of transportation."

He also cited Mayor Kenney's Vision Zero initiative to eliminate traffic-related deaths by 2030. "At times, in order to save lives, we feel the extra five minutes are worth it," Montanez said.

Even smaller towns face similar struggles. Bensalem Township is using PennDot money to upgrade traffic signals along Bristol Pike, a detour for drivers when I-95 gets backed up.

Using real-time traffic data from computerized signals will allow the signals to be more adaptable to changing patterns and conditions and ease traffic congestion, said Philip Wursta, vice president of the transportation engineering company Traffic Planning & Design Inc. and traffic engineer for several local governments, including Bensalem.

Traffic signals can adjust to allow more time for higher volumes of traffic. They "talk" to each other.

But drivers have short-term memories when it comes to traffic improvements, Wursta said. Right after the new traffic signals at Bristol Pike go up, "people will start giving us kudos," he said. But then they'll forget how bad traffic used to be and start complaining again. "We only get love for a little while," he said.

But that gets back to another question Dressler, the Philadelphia driver, had about traffic lights. How often are they maintained?

"I'm frequently the victim of lights being out," especially at Spring Garden intersections, she said. "It's always kind of shocking to me that you have a major intersection and a light could be out for hours."

Montanez said the city dispatches workers as soon as possible when a light is out — once the city knows about it. Philadelphia typically relies on drivers to call 311 to report traffic-light outages. The city has only 75 traffic-monitoring cameras spread across its roughly 3,000 signalized intersections. The city also can't control power outages.

But sometimes it's a lucky break if the lights are out and drivers determine when to go themselves, Dressler said.

"It seems," she said, "like [traffic] moves faster."