Philly traffic lights ride the green band

We check in at the halfway point of a traffic light retiming project.

Gridlock on North Broad Street.
Mark Stehle

Philadelphia has more than 2,950 intersections with traffic lights, most of which are the original, clanking electromechani­cal ones from the 1940s. The city's in the middle of a three-year project to replace the old signals along 21 major traffic corridors.
The new LED signals will connect via a fiber-optic network to a soon-to-be-built traffic operations center in North Philly, where engineers will be able to tweak the incredibly complex red-yellow-green timing remotely to keep traffic flowing and make sure pedestrians have enough time to get across streets.
We talked with Richard Montanez, chief traffic and street lighting engineer for the city, to see how the retiming project's going.

City Paper: How much is done?
Richard Montanez: About half. We're doing them in corridors — like, Broad Street being one of longer arterials, that was one of the first ones we finished. We've done Market Street, Oregon Avenue, Ara­mingo Avenue, Allegheny, Frankford, Torresdale. ... We've hit most of the major ones already, and we're now going into the smaller ones. ... The biggest change you'll see is a longer green given to side streets, so that the pedestrian has more time to cross the intersection.

CP: Any particular success stories?
RM: [Laughs.] In my job, you never fix everything for everybody. Even if you please 90 percent, it's the 10 percent you hear from. We do get a lot of thank-you letters, but most people tell us we're not doing the work right. When you have 70,000 people at the stadi­um who are sour because the Eagles lost, I can't empty them fast enough. The system's just not intended to handle that many people all at once.

CP: A German friend taught me the term "Grüne Welle," or "Green Wave," which is when a street is timed so that if you drive a certain speed, you won't hit any red lights.
RM: In the U.S., people usually call it a "Green Band," but it's the same thing. In Philly, we took two corridors in Center City, Spruce and Pine [each of which has one buffered bike lane and one car lane], and timed them for 20 mph, so that you get the bicyclists going 20 mph and the drivers going 20 mph and everybody gets the green.

CP: Are Spruce and Pine the only ones like that?
RM: No, they've all got Green Bands, it just depends on the posted speed limit and what we time it for. Most of Center City is 20 mph. Broad Street is 30 mph north of City Hall, and south of City Hall it's 25 mph. When we have a lot of bicyclist-dedicated lanes, we try to lower that to about 20 mph.

CP: How much is done by computer and how much is done by human decision?
RM: Computer programs take in data on volume, crossing times, [pedestrian] count, things like that, then give us a basic timing for an intersection. But we also use our engineering judgment to fine-tune it. We look to see whether there's a SEPTA stop, or a taxi station, or lots of deliveries — you can never really model the human factor.

CP: What don't people realize about how complicated it is to keep traffic moving?
RM: [Laughs, almost wistfully] Aw, there's a lot of things people don't realize about how complicated it is. Like, lots of people nowadays use their smartphones to avoid traffic.

CP: Has that decreased traffic?
RM: No, not decreased — it's just changed the traffic patterns. Like, in the old days, if you wanted to travel to somewhere and didn't know where you were going, you'd open up a map and you'd just follow the heaviest line — your arterials, your interstates. Now, because the smartphone can reroute you to bypass traffic in real time, people tend to use more of the road network — like, if I-95's backed up, how many people are jumping off to take local streets?

CP: Any PSAs for city drivers?
RM: Just — please be patient. Please follow all the traffic laws, obey the red lights and take your time driving. We have to respond to every fatality to see how it could have been avoided, and a lot of the time, it's because of somebody in a rush, or not paying attention, or using their smartphone. We just want everyone to be safe and careful out there — especially during the holidays.