What does adding a fourth light to traffic signals do?

Traffic engineers want to add a fourth “white” light. With the additional light, they say travel times decrease as does fuel consumption. The secret is autonomous vehicles controlling traffic flow. Autonomous vehicles communicate with the traffic signal, which the white light indicates.

The light signals that AVs are adjusting light times to help better increase flow based on communicating with other AVs in proximity. Drivers behind AVs would follow what it does. If it stops, the driver stops his car. When the AV goes through an intersection, the driver behind the AV goes through it.

Once more driver-controlled vehicles get in proximity to the signal, the white light would go dark and drivers revert to following the traditional red, yellow, and green lights. “This concept we’re proposing for traffic intersections, which we call a ‘white phase,’ taps into the computing power of autonomous vehicles themselves,” says Ali Hajbabaie, associate professor of civil, construction, and environmental engineering at NC State.