There are numerous everyday traffic scenarios that could be made safer by cars with front-facing braking indicators.

And white lights will tell human drivers to simply follow the car in front of them.” 3 Researchers at North Carolina State proposed adding a fourth light to traffic intersections.

Traffic lights would enter a "white phase" when coordinating AVs through traffic. The lack of traffic light color would also indicate to human drivers that autonomous vehicles are being controlled.

The team first introduced the idea of a fourth light in 2020, but realized a centralized system with a traffic light receiving AV signals and calculating the best route caused processing delays.