Let's say you're in a line of cars that's stopped at a traffic light, maybe with six or seven cars ahead of you. If, when the light turns green, you wonder why all the cars ahead of you don't move more quickly through the intersection, today's column is for you.
I've written before about my fascination with traffic lights, which frankly is starting to border on the unhealthy. But you can imagine how excited I was to read about a study from Oregon State University that examined the use of so-called countdown timers for drivers at traffic lights. So I called the corresponding author on the study, David Hurwitz, a transportation engineering researcher in OSU's College of Engineering. I was gratified to find someone who shared my deep interest in traffic lights, and Hurwitz was a good sport with my questions, frequently telling me that I was asking a really smart question even when we both knew otherwise.
These countdown timers tell drivers how much time remains before the current stoplight indication — red, yellow or green — will change. They're like the timers that guide pedestrians across intersections, but they're intended for drivers.
The traffic timers are used in about two dozen countries worldwide, but not in the United States. Hurwitz told me that's because federal authorities worry about providing inconsistent information to drivers at different intersections. The countdown timers only work at traffic lights that are on fixed-time schedules; that's because so-called "actuated" signals, which get their cues from metal detectors and other devices that react to real-time traffic conditions, typically change their signals one to four seconds after making the decision to change. That's not enough time for a countdown timer to be useful to drivers.
And, Hurwitz said, the countdown timers likely only would be practical in larger cities, where traffic signals are connected to a central operations system.
Still, the OSU study is intriguing. The researchers put 55 drivers behind the wheel of a full-scale driving simulator (in this case, a 2009 Ford surrounded by massive projection screens to provide what Hurwitz called "a virtual reality of sorts"). The drivers then reacted to hundreds of what traffic engineers like to call "intersection interactions," half of which involved a countdown timer that showed how much time remained before a green light turned yellow. The idea was to replicate those "dilemma zone" situations in which you're not sure whether to stop or speed up to get through the intersection.
I know what you're thinking, because that's what I thought too: My theory was that the presence of the countdown timer would prompt these drivers to speed up to beat the light.
But science has quashed another one of my theories: In fact, Hurwitz and his colleagues found that drivers in the dilemma zone with access to the countdown timer were 13 percent more likely to stop. Drivers were less likely to brake hard. They also were less likely to floor it and race through the intersection, but that's probably because I wasn't one of the drivers in the study.
The implication of the study, of course, is that the countdown timers could improve safety at intersections, and you can see why that could be a big deal: Out of the 37,000 traffic fatalities in the United States in 2016, about 20 percent of them occurred at intersections.
This new study builds on previous research about how drivers reacted to a timer displaying how much time remained before a red light turned green. (This gets to that issue of why traffic doesn't move more efficiently through stoplights.) In this case, the study confirmed what you might expect: Drivers using the timers were better prepared to move when the light turned green. In fact, the first vehicle in line moved through the intersection nearly one second more quickly. Presumably, the drivers in the cars following also would be able to move more efficiently, assuming they weren't busy texting on their cellphones. Hey! Put the phone down and drive through the intersection! The light is green!
You might be thinking that getting through a stoplight a second or so quicker isn't any big deal. But here's the way I look at it: On a typical work day, I likely get stopped at 25 or so traffic lights. Over the course of a year, these timers could save me more than two hours. I don't know what you would do with that extra time, but I would subscribe to a batch of transportation engineering journals. (mm)