Crosswalk Countdowns

New York City is installing 1500 countdown clocks in an attempt to improve pedestrian safety. I've typically found these types of signals helpful as a pedestrian, as they eliminate any questions about how much time I need to get across the street.

(from Flickr user Richard Drdul)

I've always wondered how countdown clocks influence the behavior of motorists. While their primary intent is to inform pedestrians, a secondary consequence is that they allow motorists to know exactly how much time they have to get through an intersection before the light turns.

I specifically remember from Drivers Ed when the instructor told me how to react when approaching an intersection with a "stale green" - ie. an intersection that you didn't see turn from red to green and could turn back to red at any moment. In those situations, you're supposed to take your foot off the accelerator and cover the break. That said, few seem to actually follow this rule.

Nevertheless, the question these countdown clocks raise is whether they cause motorists to behave in ways that lessen the probability of a wreck. In theory, a motorist who knows they will never make in through an intersection in time should prepare to stop early. A motorist who knows they have plenty of time doesn't need to worry about slamming on the breaks if the light suddenly turns. I'm skeptical that this is exactly how it plays out in reality, but I certainly would be interested to see some study on this question.


    I love these as both a pedestrian and a motorist.

    As a motorist, the thing I hate most in the world is that feeling that you get when you are so close to the light and it turns yellow, and you have to decide whether to go forward or slam on the breaks.

    These give me an excuse to stop early.

    On August 19, 2010 Anonymous said...

    In some of the countries I've visited in southeast Asia, they actually have a timer for the motorists! Chaos usually ensues with those running through at the last moment and those already moving in anticipation of green.


    If you're going down a stretch of street with many many timed lights (like Rt. 1 in Alexandria) you can use the pedestrian clocks to tell you whether you should speed up to avoid hitting a yellow...