N.C. State researchers: 'A ‘white phase’ taps into the computing power of autonomous vehicles'

Transportation engineers at North Carolina State University (NC State) have proposed that a fourth stoplight color be added to enhance traffic flow and improve communication between autonomous vehicles (AVs) and human drivers.

Using a "white light" signal at intersections, enabling AVs to coordinate movement and inform human drivers of the appropriate actions to take, improved travel time through intersections and reduced fuel consumption in computer simulations, researchers found in the study, titled "White Phase Intersection Control Through Distributed Coordination: A Mobile Controller Paradigm in a Mixed Traffic Stream."

“This concept we’re proposing for traffic intersections, which we call a ‘white phase,’ taps into the computing power of autonomous vehicles,” Ali Hajbabaie, corresponding author of the study and an associate professor of civil, construction and environmental engineering at NC State, told NC State News. “The white phase concept also incorporates a new traffic signal, so that human drivers know what they are supposed to do. Red lights will still mean stop. Green lights will still mean go. And white lights will tell human drivers to simply follow the car in front of them.”

According to the report, the "white phase" relies on the ability of AVs to communicate wirelessly with one another and with the traffic signal's control system. When a sufficient number of AVs approached an intersection, the system would activate the white light, indicating to AVs and human drivers that the vehicles were coordinating their movements, the report said.

Hajbabaie suggested that granting some control over traffic flow to AVs, known as the mobile control paradigm, has the potential to enhance traffic coordination in various scenarios involving AVs. However, including the white light concept at intersections would be crucial, as it would guide human drivers, allowing them to understand and adapt to traffic as they approach an intersection. The researchers also enhanced the concept of the "white phase" by using a distributed computing approach, which seeks to leverage the computational resources of all AVs involved to dictate traffic flow.

The N.C. State researchers employed microscopic traffic simulators to replicate real-world traffic behavior, including individual vehicle actions. The simulations indicated that AVs improved traffic flow compared to scenarios without AVs. The white phase also enhanced traffic flow and reduced fuel consumption by minimizing stop-and-go patterns, the report added.

The simulations demonstrated that higher percentages of AVs at white-phase intersections resulted in faster traffic movement and better fuel consumption. The researchers believe that certain aspects of the concept can be adopted with minor modifications, even if full adoption of the white-phase traffic lights takes longer. The researchers suggested pilot projects in locations such as ports with high volumes of commercial vehicle traffic.

Commercial vehicles have shown a higher rate of AV adoption, which makes ports an ideal setting to test and refine the concept, which could ultimately benefit port traffic and commercial transportation, the study said.