Bumper-to-bumper traffic may become a hassle of the past as more and more self-driving vehicles take to the roads in the coming years, according to a report by a Rutgers University–Camden team of researchers.The study found that the intelligent control of an autonomous vehicle (AV) is able to dampen stop-and-go waves of traffic that can arise.
The researcher’s experiments on a circular track with more than 20 vehicles showed that traffic waves emerge consistently, and that they can be dampened by controlling the velocity of a single vehicle in the flow.
The study compared metrics for velocity, braking events, and fuel economy across experiments, and the findings suggest a paradigm shift in traffic management — the introduction of only 5% of autonomous cars into traffic could have noticeable results.
Common wave triggers include lane changing but can even be generated in the absence of any lane changes, bottlenecks, merges or changes in grade.
Since these waves emerge from the collective dynamics of the drivers on the road, they are in principle avoidable if one could affect the way people drive.
The report’s conclusions suggest these waves can be reduced by controlling a small number of vehicles in the traffic stream.
Advanced communications systems will also be an important component for automated vehicles. The most common communication methods are vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I).
V2V communication involves one vehicle being able to inform other vehicles within a given proximity of important decisions it makes, while V2I communications involve sending information to, and accepting information from, traffic infrastructure, such as a traffic signal informing a vehicle of a red light.
Led by Benedetto Piccoli, associate provost for research at Rutgers University-Camden, the study found a single autonomous vehicle can control the flow of at least 20 human-controlled vehicles around it, with substantial reductions in excessive braking and fuel consumption.
The research comes as the use of a small number of GPS-equipped vehicles in the traffic stream has increased dramatically, changing how traffic is monitored.
Though gathering this real-time traffic data previously required predominantly fixed sensing infrastructure, recent advancements in vehicular automation and communication technologies provide new possibilities and opportunities for traffic control.
For example, when a series of adjacent vehicles on a roadway are connected and automated, it is possible to form dense platoons of vehicles which leave very small gaps, in theory eliminating the stop-and-go waves that form so-called “phantom” traffic jams.
“AVs can revolutionize the control of traffic flow,” the report noted. “They offer the potential to shift from localized control measures, like ramp metering, and centralized ones, as variable speed limit gantries, to actuators immersed in the traffic stream.”
While the presented ring experiments represent a stretch of single-lane roadway, the theory also extends to multi-lane freeways, on which lane-changing can serve as an additional trigger of stop-and-go waves.
The findings were presented to policymakers in Washington, DC at an exhibit at the Washington Auto Show, including US Sen. John Thune, chair of the Senate Committee on Commerce, Science, and Transportation.
“Most of the policymakers, car manufacturers, car dealers, and others we talked with were very impressed with the research results and got a positive feeling about autonomous vehicles,” Piccoli told Rutgers-Camden News Now. “They all agreed that the impact on real traffic economy and environmental impact could be of great importance.”
— Nathan Eddy is a filmmaker and freelance journalist based in Berlin. Follow him on Twitter @dropdeaded209_LR.
