Auto industry autonomous cars

Published on May 10th, 2017 | by Steve Hanley

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Just A Few Autonomous Cars Can Influence The Flow Of Traffic

May 10th, 2017 by  
 

It has happened to all of us. We are driving on the highway when all of a sudden traffic slows to a crawl. We assume there is an accident ahead but often traffic resumes its normal speed for no apparent reason. “What was that all about?” we wonder. A new study headed by  Daniel Work, an assistant professor at the University of Illinois at Urbana-Champaign, finds that having just a few autonomous cars on the road could reduce or eliminate such slowdowns.  “Our experiments show that with as few as 5 percent of vehicles being automated and carefully controlled, we can eliminate stop-and-go waves caused by human driving behavior,” he says.

autonomous cars

The study was funded by the National Science Foundation’s Cyber-Physical Systems program. It utilized the talents of a multi-disciplinary team of researchers with expertise in such diverse fields as traffic flow theory, control theory, robotics, cyber-physical systems, and transportation engineering. The study highlighted how important a deeper understanding of the dynamic between these autonomous vehicles and the human drivers on the road will be in designing future traffic control systems.

The  research was conducted on a test track in Tucson, Arizona. A single autonomous vehicle circled the track continuously with at least 20 other cars operated by human drivers. Under normal circumstances, human drivers naturally create stop-and-go traffic even in the absence of bottlenecks, lane changes, merges or other disruptions. This phenomenon is known as the “phantom traffic jam.”

The researchers found that by controlling the pace of the autonomous car, they were able to smooth out the traffic flow for all the cars. The study showed that even a small percentage of autonomous vehicles can eliminate those waves and reduce the total fuel consumption by up to 40 percent. “Before we carried out these experiments, I did not know how straightforward it could be to positively affect the flow of traffic,” Sprinkle said Jonathan Sprinkle, an associate professor of electrical and computer engineering at the University of Arizona. “I assumed we would need sophisticated control techniques, but what we showed was that controllers which are staples of undergraduate control theory will do the trick.”

This study suggests that adaptive cruise control systems can improve the flow of traffic even before there are large numbers of autonomous vehicles on the road. “Fully autonomous vehicles in common traffic may be still far away in the future due to many technological, market and policy constraints,” says Benedetto Piccoli, a professor of mathematics at Rutgers. “However, increased communication among vehicles and increased levels of autonomy in human-driven vehicles is in the near future.”

Programming cars for autonomous operation is more challenging when there are only a few of them on the road than it will be in the future when vehicle to vehicle connectivity is more common. “The proper design of autonomous vehicles requires a profound understanding of the reaction of humans to them,” says Benjamin Seibold, associate professor of mathematics at Temple University. “Traffic experiments play a crucial role in understanding this interplay of human and robotic agents,”  he says.

The researchers say the next step will be to study the impact of autonomous vehicles in denser traffic with more freedom granted to the human drivers, such as the ability to change lanes.

Source: Electric Vehicles Research  Photo credit: University of Illinois





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About the Author

I have been a car nut since the days when Rob Walker and Henry N. Manney, III graced the pages of Road & Track. Today, I use my trusty Miata for TSD rallies and occasional track days at Lime Rock and Watkins Glen. If it moves on wheels, I'm interested in it. Please follow me on Google + and Twitter.



  • Leeper

    Interesting to see how this occurs. Do the auto-autos leave more buffer distance and/or do they acceleration match the preceding car?
    I’m still waiting for the hive pack control that will arrange your group of cars into the most aerodynamic and efficient configuration possible. Imagine a caravan of semis that gain 25% efficiency just by driving as a road train.

    • Steve Hanley

      I think with regards to tractor trailers, that is about to happen very soon. The only thing that concerns me is how does some who wants to get off at the next exit on the highway break through a half mile long convoy of trucks driving nose to tail in the right lane?

      • Dennis Sweitzer

        I think in some open road experiments (Germany, perhaps?) they set the minimum distance between trucks large enough to allow other traffic to get through, which of course reduces the benefits.
        It seems like the ideal would be to dedicate the left lane to tightly packed vehicle platoons (which would work as long as there were no left exits).

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