Traffic lights may be getting their first major update in a century. Researchers at North Carolina State University have proposed introducing a fourth color — white — to traditional red, yellow, and green signals, to help manage traffic in a future where human drivers and autonomous vehicles share the roads.
The idea, detailed in a study published by the Institute of Electrical and Electronics Engineers (IEEE), would activate the white light only when a significant number of connected autonomous vehicles (CAVs) are present at an intersection.
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These vehicles would act as mobile traffic controllers, communicating with each other to determine the most efficient traffic flow. When the white light appears, human drivers would simply follow the vehicle in front of them.
“This concept we’re proposing for traffic intersections, which we call a ‘white phase,’ taps into the computing power of autonomous vehicles (AVs) themselves,” said Ali Hajbabaie, corresponding author of the paper. “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.”
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The study found that this distributed coordination strategy could significantly reduce congestion. Depending on the number of AVs present, intersection delays decreased between 3.2% and 94%, while overall traffic efficiency improved by up to 98.9% compared to conventional signal timing.
While the concept remains theoretical, researchers note that it offers a glimpse into a future transportation network powered by autonomous coordination. However, they acknowledge that widespread implementation would require major infrastructure upgrades, as well as a much larger share of AVs on the road than currently exists.
