Little Things That Matter: Stoplight Phasing

In Manhattan, most intersections have two stoplight phases: one permitting all north-south traffic, and one permitting all east-west traffic. Each phase lasts about 45 seconds, ensuring that pedestrians can cross even the widest avenues in one go with time to spare.

In Tel Aviv, the signalized intersections are almost never as in Manhattan. Even intersections of major streets with side streets will usually have three phases, and intersections of two major streets will usually have four, permitting conflict-free turns; turn conflicts with pedestrians exist on such intersections, but are uncommon.

From the traffic engineer’s perspective, Tel Aviv intersections are better – they’re supposed to be safer and smoother for the driver, with none of the snarl that happens when a car driving on Upper Broadway tries to turn left. They’re also hell for anyone not in a car, since waits are much longer, and to compensate for the larger number of phases each phase is shorter. This discourages enough pedestrians as to reduce the number of pedestrians for cars to hit, creating an illusion of even more safety.

If there’s enough car traffic, then streets with complex stoplight phasing are uncrossable 75% of the time. But if the street is median-divided, this is even worse, because the traffic engineers try to optimize car traffic, which means the pedestrian green on the two halves of the street is unsynchronized. At some intersections, one direction of a crossing is pessimized for the pedestrian: that is, after crossing one half of the street, the pedestrian will have to wait nearly a full cycle to cross the other half.

There are emerging calls for complete streets, which include such important features of walkability as wide sidewalks and frequent crosswalks. But the frequency of the crosswalks is only partial consolation if the stoplights are optimized for high car speed rather than high walking speed. For a healthy, young individual, the difference between not having to wait at intersections and having to wait a minute and a half every 300 meters is the difference between walking at 6 km/h and walking at 4 km/h. Traffic engineers do not tolerate phasing that slows down cars by 33%, and should not tolerate phasing that so slows down pedestrians.

The above does not apply as much to low-traffic areas such as Downtown Athens, Georgia, because there are sufficiently few cars that locals ignore pedestrian stoplights anyway. But in a large city with many cars such as Tel Aviv, it’s difficult to cross safely on red. As a result, streets that are no wider than a Manhattan avenue can take multiple minutes to cross, and one such street, Ibn Gabirol, divides the neighborhood it passes through in a way that 42nd and Broadway never do.

Ibn Gabirol and similar streets are not suburban arterials. They’re not like Athens’ Baxter Street. They have a street wall, very wide sidewalks, and mixed uses, just like Manhattan avenues. They also have enough foot and car traffic that they don’t feel desolate. They feel very walkable, as long as you stay on one side; it’s when you try to cross that their auto-oriented nature becomes apparent.

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8 Responses to Little Things That Matter: Stoplight Phasing

  1. Kristin says:

    Interesting calculation about how complex phased signals slow down pedestrians and how such delay would not be acceptable for vehicle traffic! Another pedestrian pet peeve: walk lights that must be activated with a button, causing even more delay if the pedestrian is just a moment too late in the cycle.

    • Alon Levy says:

      Oh yeah, the pedestrian buttons are just stupid. In Athens we were told they only prolong the pedestrian green by 7 seconds, and pretty much ignored them and crossed whenever there were no cars conflicting. Fortunately, Tel Aviv doesn’t have them in the urban core (but does have them on some arterials in outer-urban areas); a pedestrian will eventually be able to cross without pressing a button, but it may take a while.

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  7. Mark says:

    In Tel Aviv I think one really needs a separate phasing for cars turning right as drivers are very aggressively trying to squeeze past crossing pedestrians. I am always amazed how many drivers I spot doing stuff on their mobiles whilst coming around the corner!!

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