Connected cars and artificial intelligence could reduce or eliminate most highway congestion. That’s the theory behind a research program called CIRCLES, an acronym that stands for Congestion Impacts Reduction via CAV-in-the-loop Lagrangian Energy Smoothing. With a name like that, it’s no wonder the researchers decided to use an acronym!
According to its website, CIRCLES seeks to reduce instabilities in traffic flow, called “phantom jams,” that cause congestion and waste energy. If you have ever encountered a temporary traffic jam for no apparent reason, this might have been a phantom jam that occurred naturally because of human driving behavior.
Prior work on closed-course testing demonstrated that phantom jams can be reduced using autonomous vehicle technologies and specially designed algorithms. The CIRCLES project seeks to extend this technology to real world traffic, where reducing these negative traffic effects could provide ≥10% energy savings.
The CIRCLES Research
CIRCLES is composed of researchers at UC Berkeley and the Institute of Transportation Studies (ITS) Berkeley, in coordination with Vanderbilt University, University of Arizona, Temple University, Rutgers University-Camden, the Tennessee Department of Transportation. Toyota North America, General Motors, and Nissan are also involved in the research effort.
The idea for CIRCLES comes from an experiment conducted in Japan a decade ago. Drivers in 20 identical cars were asked to drive at a constant speed around a circular track. Within a few minutes, clumps of cars were stopped at one part of the track while other drivers were racing to catch up to the cars ahead. Humans just aren’t very good at operating automobiles under such conditions.
We have all seen it happen. The car in front taps the brakes because a squirrel is crossing the road or the driver wants to gawk at an accident on the other side of the highway. Soon, everybody behind has jammed on their brakes and traffic slows or comes to a halt. It can take minutes or even hours for the slow down to clear.
Recently, the researchers conducted an experiment on a 15-mile long section of Interstate 24 near Nashville, Tennessee. It used 100 cars that traveled in loops from about 6 a.m. to 9:45 a.m. each morning. Working on the premise that if 5% of the cars on the road were acting together they could lessen the prevalence of phantom traffic jams, the researchers equipped those 100 cars so they could communicate with each other wirelessly and send traffic information back and forth between all the cars.
In the experiment, the adaptive cruise control in each car was modified to react to the overall traffic flow — including what was happening far ahead — using artificial intelligence.
Daniel Work, a professor of civil and environmental engineering at Vanderbilt University, tells the Associated Press the decision-making by the connected cars occurred on two levels. At the cloud level, information about traffic conditions was used to create an overall speed plan. That plan was then broadcast to the cars, which used artificial intelligence algorithms to determine the best action to take. The researchers were able to evaluate the effect the connected cars had on morning traffic flow using a special 4-mile stretch of I-24 outfitted with 300 pole-mounted sensors.
Liam Pedersen is deputy general manager for research at Nissan who was in Nashville last week for the experiment. He said one of the exciting things about it is that it builds on technology that is already in many new cars. “This is not autonomous driving,” he said. “This is something we could realize very soon.” Asked if automakers will be willing to cooperate to ease traffic, he said, “I certainly hope so, because the system works best when lots and lots of cars participate.”
Connected Cars & Congestion
The recent experiment in Tennessee was suggested by research Work did at the University of Arizona in 2017. He and his associates recreated the Japanese circular driving experiment with one twist. They added one autonomous car to the mix. The self-driving car smoothed the flow of traffic so that there were 98% fewer braking incidents. That led to a 40% increase in fuel efficiency and a 14% increase in distance driven during the time allotted for the experiment. You can see the results for yourself in this video.
Researchers are still crunching the numbers on last week’s experiment, but Work says it “demonstrated that these jams can be reduced through the novel automated vehicle technologies we developed. It’s unquestionable that enhanced automotive technology can significantly reduce phantom traffic jams when implemented at scale.”
Still, he cautioned that the technology is not going to suddenly eliminate congestion. “When there are more cars on the road than the road can support, there will always be traffic,” he said. “But this can make that congestion less painful.”
Many years ago, Elon Musk was frustrated because he was stuck in traffic on the way to the airport in Los Angeles. Suddenly, a thought occurred to him. Why not bore tunnels deep underground and bypass all this surface congestion altogether? Voila! The Hyperloop was born. Since then, millions have been spent trying to create a business case for the idea, but so far it remains just that — an idea whose time never arrived.
What the CIRCLES research shows is that there may be a better way to address traffic jams with technology that already exists today. No $15,000 autonomous driving software suites. No Lidar or liquid cooled supercomputers hidden away behind touchscreens. What CIRCLES is proposing might add $200 to the price of a new car.
Connected cars would need an internet connection and some sensors along the side of highways to get 80% of the benefits of full self-driving for less than 5% of the cost. Would you take that deal?
Yes, we know. It won’t help much in midtown Manhattan or any other large city where congestion has been with us for a century or more. And it won’t change lanes automatically or navigate highway interchanges without benefit of a human driver. But this may be the best example of a situation in which we shouldn’t let the perfect be the enemy of the good.
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