Traffic lights could have a fourth color in the future. Here’s why. : Science alert

In a hypothetical future where autonomous cars cruise up and down our busy streets, traffic lights could have a fourth color added in favor of these self-driving vehicles.

Researchers from North Carolina State University propose an additional white traffic light that would signal drivers that autonomous vehicles (AVs) are intelligently managing the upcoming traffic flow intersection. The reasoning is that both the level of congestion and overall fuel consumption could be reduced.

The self-driving cars and trucks no longer have to “look” at the white traffic light because they communicate with it wirelessly. However, it will serve as a cue for human drivers and passengers to follow the lead of the self-driving vehicles moving through the intersection.

Traffic light white phase
Researchers propose a new white phase for crossbreeds. (Niroumand et al., IEEE Transactions on Intelligent Transport Systems, 2023)

“Red lights still mean stop. Green lights still mean go. And white lights will tell human drivers to just follow the car in front of them,” says civil engineer Ali Hajbabaie.

“This concept, which we propose for transport hubs, which we call ‘white phase’, uses the computing power of autonomous vehicles.”

How it would work: Autonomous vehicles would communicate with each other and with the traffic lights at intersections within a certain range. This would allow them to coordinate the flow of traffic more efficiently and intelligently – for example, giving priority to converging roads with more vehicles and recommending optimal speeds.

All human drivers in the mix would be informed to follow the guidance of the vehicle in front of them via the white light: stop when it stops, continue when it continues. Once the number of autonomous vehicles at an intersection drops below a certain threshold, the traffic lights would switch back to the normal red, amber, and green option.

In simulated models, AVs have been shown to inherently improve traffic flow, even more so when white phase was introduced – which then has a positive impact on fuel consumption reduction. The higher the percentage of AVs at an intersection, the faster the traffic was moving, with potential improvements of around 40 to 99 percent in terms of overall delay reduction.

“Giving AVs some of the control of traffic flow is a relatively new idea, dubbed the mobile control paradigm,” says Hajbabaie. “It can be used to coordinate traffic in any scenario involving AVs.”

“But we think it’s important to integrate the white light concept at intersections because it tells human drivers what’s going on so they know what to do when they approach the intersection.”

The researchers note that the improvements become more significant once the number of autonomous vehicles at an intersection increases above 30 percent. With 70 percent AVs in traffic, the intersection can usually be driven in fully automatic white phase mode.

We don’t yet have the technology to implement something like this, although improvements are constantly being made. This study builds on an earlier investigation by the same researchers in 2020, in which traffic flow was controlled by a central computer connected to the intersection – here the required computing power can be managed by the self-driving cars themselves.

Upgrading each intersection will obviously take time and money, but the researchers believe certain aspects of the white phase idea could be implemented with relative ease. Test runs in certain areas could be the next step.

“Ports have a high volume of commercial vehicle traffic, for which traffic flow is particularly important,” says Hajbabaie. “Commercial vehicles appear to have a higher rate of autonomous vehicles, so there may be an opportunity to implement a pilot project in this environment that could benefit port traffic and commercial transportation.”

The research was published in IEEE Transactions on Intelligent Transport Systems.

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