Transportation engineers at North Carolina State University are proposing a bold upgrade to traffic signals. The idea introduces a fourth white light, known as the “white phase.” This signal is designed specifically for intersections where self-driving cars are present.
When activated, connected autonomous vehicles communicate wirelessly with one another. They coordinate traffic flow as they pass through the intersection. Meanwhile, human drivers are guided to simply follow the vehicle directly in front of them.
According to Ali Hajbabaie, an associate professor of civil and environmental engineering at NC State, the system relies on a distributed computing model. Each autonomous vehicle acts as a mini-processor. This makes the system more resilient to communication failures compared to a centralized traffic control system.
Simulations published in IEEE Transactions on Intelligent Transportation Systems show strong potential benefits. The white phase system could reduce total intersection delays by between 40% and 99%. It may also lower fuel consumption. In safety conflict analyses, the system recorded zero near-collision cases.
The researchers believe early real-world trials could begin in high-traffic commercial areas. These include seaports, where autonomous freight trucks are already being adopted more widely. They also note that benefits can start to appear even when only 10% of vehicles at an intersection are autonomous.
