As a pedestrian, the numeric countdown timers on crossing signals make life so much easier. No more are we doomed to grapple with the uncertainty of what exactly that orange "Don't Walk" hand means—is it "Don't Walk (The Light Is Turning Now)" or is it really saying "Don't Walk (Unless You Can Cross the Street in Less than 16 Seconds)"? You know when to walk briskly, and when you can take your time.
Unfortunately, what makes pedestrians safer may have the inverse effect on traffic. Drivers, too, can usually see the seconds counting down, and some of them decide to speed up to beat the light. Others, naturally, see only a few seconds left on the clock and decide to slow down—leading to a lot of rear-endings.
[T]he biggest increases in crashes come at intersections that were previously safe intersections. And they think this is because at busy intersections traffic is clogged, you can't really speed through. But at safe intersections, the countdown timers now are causing the drivers to actually speed up. They also find, and this is really disturbing, the effect of installing these timers seems to go up with time. In other words, the more drivers get used to the timers, the more their behavior seems to change. So it may be that I used to say, I'm going to floor it when I see two seconds left, but now I've learned that I can floor it and get through the intersection when there's only one second left. And now I'm going even faster and taking an even bigger risk.
Not all researchers agree on this effect. Some have found the opposite: that the timers help drivers improve their driving decisions—but many of these studies have used a much smaller sample (and smaller cities in general) than the Toronto research, looking at only 106 intersections in Charlotte, North Carolina, for instance, or four intersections in Lawrence, Kansas.
If countdown timers do really speed some drivers up, herein lies a design opportunity. The U.S. Department of Transportation's traffic manual mandates that countdown displays be used in traffic crossings that take more than seven seconds for pedestrians to clear, and the signals have become commonplace in many cities. A redesign could make pedestrian signals less noticeable to drivers—perhaps by placing the countdown timer elsewhere or angling it to be visible only to pedestrians, not cross traffic. Or perhaps it's not visible at all: Vendatam suggests creating an audio countdown that people in cars wouldn't be able to hear. Surely there's a way to retain the pedestrian safety benefits of a countdown, without encouraging drivers to have a Gone In 60 Seconds moment.