NASHVILLE, Tenn. (AP) — As millions of people hit the highways this Thanksgiving, many will encounter traffic jams for no apparent reason — no construction site or accident. Researchers say the problem is you.
Human drivers simply don’t do a good job of navigating heavy traffic, but an experiment using AI in Nashville last week means help could be on the way. In the experiment, specially equipped cars were able to ease rush hour congestion on Interstate-24, researcher Daniel Work said Tuesday. In addition to reducing driver frustration, Work said less stop-and-go driving means fuel savings and, by extension, less pollution.
The civil and environmental engineering professor at Vanderbilt University is one of a group of engineers and mathematicians from universities across the United States who have been studying the problem of phantom traffic jams after a simple experiment in Japan a dozen years ago showed how they develop. The researchers put about 20 human drivers on a circular track and asked them to drive at a constant speed. Before long, traffic went from a regular flow to a series of stops and starts.
“Phantom traffic jams are created by drivers like you and me,” Work explained.
A person touches the brakes for any reason. The person behind them takes a second to respond and has to brake even harder. The next person has to brake even harder. The wave of braking continues until many cars are stationary. Then, when traffic clears, drivers accelerate too fast, causing more braking and another traffic jam.
“We know that a car that brakes suddenly can have a huge impact,” Work said.
Last week’s experiment showed that even some cars that drive slowly and steadily could have an impact, for the better.
The experiment used 100 cars that traveled in a loop on a 15-mile section of I-24 from approximately 6:00 a.m. to 9:45 a.m. each morning. Assuming that if 5 percent of the cars on the road acted together, they could reduce the prevalence of phantom traffic jams, the researchers equipped those 100 cars to communicate wirelessly, sending traffic information back and forth.
They also took advantage of the adaptive cruise control which is already an option on many new vehicles. This technology allows the driver to set a car to navigate at a certain speed, but the car automatically slows and accelerates as needed to maintain a safe distance from the car in front. In the experiment, adaptive cruise control was modified to react to overall traffic flow, including what was happening far ahead, using artificial intelligence.
The decision-making process of the cars took place on two levels, Work said. At the cloud level, information about traffic conditions was used to create an overall speed plan. That plan was then fed to the cars, which used AI algorithms to determine the best action to take. The researchers were able to evaluate the effect of connected cars on morning traffic flow using a special 4-mile stretch of I-24 equipped with 300 pole-mounted sensors.
The experiment is a project of the CIRCLES consortium, a group that includes several automakers and the US departments of energy and transportation. Other principal investigators are based at the University of California, Berkeley; Temple University; and Rutgers University-Camden.
Liam Pedersen is deputy director general for research at Nissan, a partner in the CIRCLES consortium that was in Nashville last week for the experiment. He said one of the cool things is that it’s based on technology that’s already in a lot of new cars.
“This is not autonomous driving,” he said. “This is something we may be realizing very soon.”
Asked if the automakers will be willing to work together to ease the traffic, Pedersen said, “I certainly hope so, because the system works best when lots and lots of cars participate.”
Last week’s experiment was built on work and his colleagues conducted in 2017 at the University of Arizona. This repeated the Japanese experiment, this time with a single self-driving car thrown into the mix. The self-driving car has smoothed out the flow of traffic so that there was 98% less braking. This resulted in a 40% increase in fuel efficiency and a 14% increase in mileage.
The researchers are still crunching the numbers from last week’s experiment, but Work said it “proved that these jams can be reduced through the new automated vehicle technologies we’ve developed. It is indisputable that advanced automotive technology can significantly reduce phantom traffic jams when implemented on a large scale.
However, he warned that technology won’t suddenly eliminate congestion.
“When there are more cars on the road than the road can support, there will always be traffic,” he said. “But that can make that congestion less painful.”