Will a white light be added to traffic signals for self-driving cars?

The potential of fourth, white light to be added to traffic lights could be used to help human drivers yield for self-driving cars, experts say.

The autonomous driving systems installed on a test vehicle that drove in various scenarios in real-time on a physical test surface at the Shlomo Group Arena in Tel Aviv. (photo credit: OMRI REFTOV)
The autonomous driving systems installed on a test vehicle that drove in various scenarios in real-time on a physical test surface at the Shlomo Group Arena in Tel Aviv.
(photo credit: OMRI REFTOV)

Red, yellow, green, and white lights? The future of traffic signals might involve an additional hue, according to a study by experts from the North Carolina State University. As the prevalence of autonomous vehicles continues to rise, researchers envision a new fourth light — the white light — specifically designed for self-driving cars.

The findings of this study were published in the peer-reviewed journal IEEE Transactions on Intelligent Transportation Systems.

Enhancing traffic flow with white traffic signal light

In a bid to enhance traffic efficiency and reduce congestion, adding a "white light" to traffic signals could serve as a signal for human drivers to yield to autonomous vehicles at intersections, according to a report on the science website iflscience. While autonomous cars and trucks would communicate wirelessly with the white light, human drivers would be prompted to acknowledge the presence of self-driving cars and act accordingly.

Through simulations, researchers have been able to show that incorporating a fourth traffic signal light, most likely white, would improve situational awareness for human drivers while enabling autonomous vehicles to control traffic flow effectively, resulting in saving time and fuel.

Self-driving car (Illustrative). (credit: JPOST STAFF)
Self-driving car (Illustrative). (credit: JPOST STAFF)

Ali Hajbabaie, the author of the study, explains, “This concept we're proposing for traffic intersections, which we call a 'white phase,' taps into the computing power of autonomous vehicles (AVs) themselves. 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."

When the white light is lit up, autonomous vehicles would have full control over the intersection. By leveraging wireless communication between vehicles, precise positioning, and advanced decision-making capabilities, they would coordinate movements and optimize traffic flow. However, it is worth noting that when there aren't any self-driving cars, the traditional red-yellow-green lights would regulate traffic as usual.

The researchers emphasize the importance of the fourth light's color being unanimously agreed upon internationally, suggesting that white is not a definitive choice.

Initial tests using simulations and computer models have demonstrated promising results. The presence of the white light led to incremental improvements in traffic, especially when autonomous vehicles constituted between 10% and 30% of the total vehicles. At 30%, delays decreased by a significant 10.7%, and as the number of self-driving cars increased, traffic improved even further. This indicates the potential for dramatic enhancements in traffic signal efficiency, surpassing the limitations of conventional timed stop-start systems.

Nevertheless, while simulations show positive outcomes, the introduction of such a comprehensive system may present challenges for actual drivers, considering its added complexity.

The researchers acknowledge the difficulties associated with implementing a new system but advocate for pilot trials. Hajbabaie suggests, "There are various elements of the white phase concept that could be adopted with only minor modifications to both intersections and existing AVs. We also think there are opportunities to test drive this approach at specific locations. For example, ports see high volumes of commercial vehicle traffic, for which traffic flow is particularly important. Commercial vehicles seem to have higher rates of autonomous vehicle adoption, so there could be an opportunity to implement a pilot project in that setting that could benefit port traffic and commercial transportation.

The study sheds light on the potential integration of white lights into traffic signals, enabling efficient collaboration between autonomous and human-driven vehicles. Although further research and trials are necessary, this innovative concept holds promise for revolutionizing traffic management in the era of autonomous transportation.