Stoplight Countdown Timers Improve Safety at Traffic Intersections: Study

New research suggests that the use of traffic signal countdown timers could help drivers better prepare for red lights, reducing the risk of accidents at traffic intersections. 

In a study published online for the November issue of the journal Traffic Research, researchers indicate that driving simulator test demonstrate that Traffic Signal Countdown Timers (TSCTs) increased the probability for drivers to stop by 13.10% when approaching an intersection.

The research was led by Mohammad R. Islam, of the School of Civil and Construction Engineering at Oregon State University, where 55 participants, including 32 males and 32 females, responded to 1,100 simulated traffic signals. Half of the simulated traffic signals were Green Signal Countdown Timers (GSCTs) and the other half were TSCTs.

Researchers focused on how drivers responded to each traffic signal approach and exactly when drivers began stopping before an intersection.

The study was designed to identify if a numerical presence at intersection lights would improve decision making abilities and better help drivers make informed choices on when to begin decelerating and accelerating.

According to the data, the presence of a green-light countdowns increased the average stopping probability by 13.10 percent while decreasing the average driver deceleration rates by 1.50 feet per seconds. Researchers noted in the study that the presence of a multi-color light signal in conjunction with a countdown timer improved intersection safety.

Researchers stated that the use of the countdown timers helped drivers understand when a traffic signal was going to turn from green to yellow, which is one of the most crucial moments when approaching an intersection.

By assigning a numbered timer, participants were able to predict when the light was going to turn yellow, and mentally make the decision that they were about to begin stopping, rather than making a split-second decision to start braking when the light quickly changed from green to yellow, researchers determined.

A similar 2006 report from the Institute of Transportation Engineers in Washington, D.C., concluded that countdown signals did not change the number of drivers running red lights, however they reduced pedestrian-involved crashes at intersections by 52 percent.

Some automakers, such as Audi, have implemented Traffic Light Information technology in vehicles, which count down the time until the traffic light at the intersection in front of the driver will turn green. The technology is displayed on the dash, and when the indicates the speed limit and the estimated countdown time to green but disappears once it reaches within 3 seconds to green to deter drivers from racing. The automaker claims the technology has the potential to save fuel, smooth traffic flow, and reduce driver stress.

Researchers noted that the timers are an innovative, practical, and cost effective technology that could be implemented across the United States at a reasonable cost to significantly improve safety at signalized intersections.