Autonomous vehicles key to ‘white phase’ traffic flow efficiency

This is the claim of researchers at North Carolina State University (NC State) who believe the presence more autonomous vehicles would shorten waiting times for everyone. The team’s findings are detailed in Computer-Aided Civil and Infrastructure Engineering.

Earlier work at NC State showed that a fourth white phase traffic signal would use the computing power of autonomous vehicles (AVs) to expedite traffic at intersections

In a statement, Ali Hajbabaie, corresponding author and associate professor of civil, construction and environmental engineering at NC State, said: “We had not yet incorporated what this concept would mean for pedestrians. We’ve now expanded our computational modelling to account for foot traffic, and the results are extremely promising for both pedestrians and vehicles.”

The white phase concept makes use of AVs’ ability to communicate wirelessly with each other and the computers that control the traffic signals.

The new white light would indicate to human drivers that they should follow the car in front of them, a manoeuvre activated when enough AVs are approaching the intersection.

According to NC State, the white light effectively becomes a signal that AVs are coordinating their movement to facilitate traffic through the intersection more efficiently.

“Our previous research found that the more AVs there are on the road, the more efficiently the traffic moves,” said Hajbabaie. “To be clear, this improves travel time, fuel efficiency and safety for all of the cars on the road – not just AVs.”

To account for pedestrian traffic, the researchers incorporated a suite of new parameters into the optimisation model that assessed the impact foot traffic would have on all traffic through an intersection.

“We found that, when pedestrians are added into the mix, the white phase concept still improves traffic efficiency for everyone,” said Hajbabaie. “And, again, the higher the percentage of traffic that is made up of AVs, the more efficiently traffic moves through intersections.

“If at some point in the future we see almost universal adoption of AVs, our models suggest that delays at intersections would decrease by more than 25 per cent. More realistically, we will eventually see a lower percentage of wirelessly connected AVs on the road, but there would still be meaningful improvements in traffic time.”

The researchers know that governments will not be adopting these new traffic technologies in the immediate future, but are already taking steps to ensure that future pilot projects will be safe and effective.

“We are currently setting up a physical testbed that will allow us to experiment with this concept in the physical world – not just in a computer model,” said Hajbabaie. “However, the vehicles we are using in the testbed are small enough to hold in your hands. This will help us identify challenges in implementation without the expense – and safety risk – involved with using full-scale vehicles.”