Safety Feature For Pedestrians Has Undesired Consequence

Safety Feature For Pedestrians Has Undesired Consequence

Shankar Vedantam

New analysis finds that the countdown clocks telling pedestrians how much time they have to cross the intersection actually increase traffic crashes.


Many cities and towns have installed a safety feature for pedestrians at traffic signals, you might have seen them. When the signal changes to tell people when to cross an intersection, a timer appears. It alerts pedestrians to how much time they have to cross the road. Well, there’s new evidence that the safety feature might actually be having a dangerous and unintended consequence. NPR’s Shankar Vedantam joins us each week on this program to talk about social science research. And, Shankar, I know this countdown signal well. I see it as a driver, I see it as a pedestrian. What’s the danger here?

SHANKAR VEDANTAM, BYLINE: Well, the danger is that pedestrians are not the only ones who can see this countdown timer. Drivers can see the timer too and as the timer starts winding down to two or three seconds the driver knows the traffic light is about to turn red and that makes some of them speed up to get through the intersection.

GREENE: Well, beyond speeding up, you know, and potentially getting a ticket, is there even more danger here?

VEDANTAM: Yeah, I spoke with Arvind Magesan, he’s a researcher at the University of Calgary. And along with his co-author, Sacha Kapoor, they looked at the effect of installing these countdown timers at nearly 1,800 intersections in the city of Toronto. Now, the news is not all bad. The timers lowered the number of accidents involving pedestrians. In other words, when people know how much time they have to get across the intersection, it helps them get across safely or decide not to start in the first place. But the timers also increase collisions between cars. And Magesan told me there was one particular kind of crash that seemed to go up. Here he is.

ARVIND MAGESAN: The largest increase is in rear-end accidents and we think it’s because two cars approaching a light, who both see the countdown, the guy behind, he sees the two or three seconds and thinks, oh, the guy in front of me is going to floor it too, I’ll floor it and we’ll both get through the intersection. Whereas the guy in front thinks, OK, I only have two or three seconds left, I’m going to slowdown. And this is exactly the type of accident that would happen in that case.

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