Researchers propose a fourth light at traffic lights – for autopilots

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North Carolina State University transportation engineers are now proposing to add “white light” to traffic lights, which will allow vehicles on autopilot to control traffic flow and the situation on the road. In computational modeling, a new approach significantly reduces travel time through intersections and reduces fuel consumption.

“This concept that we propose for interchanges, which we call “white phase”, uses the computing power of autonomous vehicles (AVs) themselves. The white phase concept also includes a new traffic light signal to let drivers know what they should be doing. Red lights will still mean stop. Green lights will still mean move. And white lights will tell drivers to just follow the car in front of them, &mdash ; says Ali Haibabaye, author of the article and assistant professor of civil and environmental engineering at NC State.

The white phase concept is based on the fact that the AVs can communicate wirelessly both with each other and with the computer controlling the traffic signal. When enough AVs approach an intersection, this will activate the white light. The white light is a signal that the drones coordinate their movement to ensure more efficient movement through the intersection. Any non-automated vehicles — human-driven — are simply required to follow the vehicle in front of them: if the car in front of them stops, they stop; if the car in front of them passes the intersection, they pass the intersection.

When there are too many vehicles approaching the intersection, drivers control rather than the autopilots, the traffic lights will revert to the normal green-yellow-red signal pattern.

"Giving autonomous vehicles a portion of traffic flow control — a relatively new idea called the mobile governance paradigm”, — Hybabaye says.— “It can be used to coordinate traffic in any scenario involving AV. But we think it's important to include the concept of white light at intersections because it tells drivers what's going on so they know what they should do when approaching an intersection. And, to be clear, the color of “white light” does not matter. It is important that there is a signal that drivers clearly identify.

Researchers first introduced the concept of the “white phase” traffic interchange in 2020. However, this initial concept was based on a centralized computing approach where the traffic light computer was responsible for getting data from all approaching AVs, doing the necessary calculations, and then telling the AVs how they should proceed through the intersection.
< br />"We have improved on this concept and this paper describes the white phase concept based on distributed computing — efficient use of computing resources of all AVs to control traffic flow. This is both more efficient and less likely to fall victim to communication failures. For example, if there is an interruption or delay in communication with a traffic light, the distributed computing approach will still be able to seamlessly handle the flow of traffic,” — Haibabaye says.

To test the performance of the white phase concept of distributed computing, the researchers used microscopic traffic simulators. These simulators are complex computational models designed to simulate real traffic, down to the behavior of individual vehicles. Using these simulators, the researchers were able to compare traffic behavior at intersections with white phase and without it, and how the number of AVs involved affects this behavior.

"Modeling tells us a few things — Hybabaye says.— Firstly, AVs improve the traffic flow regardless of the presence of white phase. Secondly, if AVs are present, the white phase improves the traffic flow even more. This also reduces fuel consumption, since the number of stops is reduced. Thirdly, the higher the percentage of traffic at an intersection with a white phase consisting of AV, the faster the traffic moves through the intersection and the better the fuel consumption performance.

When only 10-30% of the traffic at a white phase intersection was autonomous vehicles, simulations showed that there were small improvements in traffic flow. But as the percentage of AVs at white phase intersections increased, so did the benefits.

“However, even if only 10% of the vehicles at a white phase intersection are autonomous, you will still see fewer delays. For example, when 10% of vehicles are autonomous, you see that delays are reduced by 3%. When 30% of vehicles are autonomous, delays are reduced by 10.7%, — Haibabai says.

Researchers acknowledge that AV is not ready to embrace a new approach to distributed computing tomorrow, and governments are not going to install new traffic lights at every intersection in the near future. However, there are various elements of the white phase concept that could be implemented with only minor modifications in both intersections and existing autonomous vehicles in order to start testing this approach in specific locations, the researchers say.

For example , ports see a high volume of commercial traffic for which traffic flow is particularly important. Commercial vehicles seem to have higher adoption rates of self-driving vehicles, so it may be possible to implement a pilot project under these conditions, which could benefit port traffic and commercial transport.

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