RALEIGH, N.C. — Drivers are familiar with red, yellow and green lights.

North Carolina State University researchers conducted a study that found adding a fourth light would improve traffic flow at intersections and would involve self-driving cars.

Ali Hajbabaie, co-author of the study, said the greater number of autonomous vehicles on the road, the more efficient traffic will move through intersections. She said the system would improve flow by 25% and explained how the system works.

“[One] car is in charge of three cars that are following it, and now, this car talks to other autonomous cars and also with the traffic controller and negotiates a safe right of way for the group of cars to go through the intersection,” Hajbabaie said.

The fourth light comes in for human-driven cars, which would follow the autonomous car in front of them.

“Our results show that not only in the travel reductions in the travel time of autonomous cars, we have similar reductions in travel times of human-driven vehicles, and also we are reducing the delay time of pedestrians that want to go through the intersection,” Hajbabaie said.

Hajababaie said computer modeling shows this system produces fewer crashes too. She said it could mean we see the end of green lights.

“How intersections are going to look like 20,30, 40 years from now when all cars are autonomous?” Hajababaie said. “And we said probably we don’t need a traffic light at the intersection.”

The next step for researchers is to test the concept on the road. It’s years away from use in the real world, Hajababaie said.