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With autonomous cars on the road, researchers look into adding white lights to traffic signals

Researchers looking into adding white light to traffic signals
Researchers looking into adding white light to traffic signals 04:34

(CBS DETROIT) — Anyone who has gotten behind a wheel knows the feeling of being stuck at a red light, and researchers are working on ways to reduce that occurrence. One way to do this is by changing traffic signals.

A Detroit police officer is credited with adding the yellow light to traffic signals in 1920. Now, 100 years later, some are considering adding another.

As more autonomous vehicles enter our roadways, traffic flow can improve because they can communicate with each other. However, they still have to share the road with human-driven cars. 

"And that's when the white light concept started," said Ali Hajbabaie, an associate engineering professor at North Carolina State University.

He has been researching how to use autonomous vehicles to make traffic systems safer, more efficient, and more environmentally friendly for all cars on the road.

Through his research, he found that adding a fourth traffic light may be helpful. Their "white phase" can work when 30-40% of the cars on a given road are autonomous. The light itself could be any color or flashing light, but what's important is what it would signal.

When illuminated at an intersection, it would let human drivers know that there are enough AVs on the road, and they would communicate with each other to control the right of way at the intersection.

Human drivers would follow their lead at a normal driving distance. Slowing and stopping when they do, or continuing through an intersection if that's how traffic is flowing.

"Only thing that human-driven vehicles need to do is adjust to follow the vehicle in front of them," said Hajbabaie.

He said the system reduces travel times by 10%, even more, if more AVs are on the road. The technology requires level 2 or 3 autonomous cars with autonomous cruise control and lane assist capabilities.

"But if you don't have enough AVs, it's going to revert back to green, yellow, and red. And you go through the intersection like now.

Their computer models also showed that the system reduced energy consumption and improved safety for all cars on the road, including AVs and human-driven ones.

Hajbabaie and his team are also investigating ways to use AVs to improve freeway merging and traffic flow through roundabouts. 

While a new traffic signal might be in the future, researchers in Michigan are working to optimize intersections without new lights or autonomous cars. 

"And the beauty of this is we do not need any infrastructure-based sensor information," said Henry Liu, the director of Mcity at the University of Michigan.

He and his team have been investigating the data our internet-connected cars share to evaluate a traffic signal's performance. They've tested this in Birmingham, collecting data from its 34 intersections.

"If the car is stopped at like 100 feet from the intersection, then we know roughly about four cars are in front of that car," said Liu.

They then adjusted the traffic signal's timing, adding longer or shorter green lights depending on the number of cars.

"Across multiple intersections, we can reduce the number of stops by 40%, just by coordinating these intersections better."

He said this is a more cost-effective way to improve intersections. The next phase of that project will be to connect the data from the cars directly to the traffic lights so the lights can make adjustments to traffic flow in real-time.

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