Motorists who find themselves stopped at an intersection will arrive at their destination faster if traffic signals give motorists notice before the light changes to green. A team of Belgian researchers from Hasselt University presented their findings on the "starting yellow" idea to the Transportation Research Board in Washington, DC earlier this year.

Germany and the UK already use the system, which flashes the traffic signal's yellow light one or two seconds before the green light illuminates. The idea is to give motorists a chance to prepare to get moving by placing their cars in gear, or putting down their mobile phones. As in the United States, Belgium does not permit the use of starting yellow lights. So the researchers used a driving simulator to investigate the effects of the idea on traffic flow and safety.

Motorists can take as much as three or four seconds to get moving after a light turns green. This is because it takes time for a driver to notice the change in the traffic signal and respond by pressing the accelerator. It then takes even more time for the car to get up to speed, particularly for slower and heavier vehicles.

Forty-four test subjects of various ages used the driving simulator to explore a number of scenarios by traveling through intersections with and without the two-second starting yellow system. The evaluation looked for potential conflicts with pedestrians and other vehicles. The testing revealed that drivers took an average of 3.5 seconds to get moving, a time that dropped to 2.4 seconds when the starting yellow was displayed. No safety problems were found, since Belgium uses a two-second all-red phase to prevent traffic conflicts.

After trying out the system, thirty-nine of the participants agreed that it would be worth implementing, while one participant found the system confusing. The researchers concluded that a longer-term study under real-life conditions would produce more accurate results.

A copy of the study is available in a 700k PDF file at the source link below.