Self-driving cars could put end to traffic jams
Driving around on summer weekends or heading out on vacation, travelers often find themselves caught in a “phantom” traffic jam that defies explanation.
Well, just in time for road trip season, a National Science Foundation study reveals that having a single selfdriving car on the road can reduce congestion by influencing the traffic flow of at least 20 human-controlled automobiles around it. In fact, simply using the cruise-control systems that are installed in many everyday vehicles can put a dent in traffic snarls, a follow-up study in collaboration with Ford found.
“In some circumstances, adaptive cruise control is enough to mitigate some of the breaking traffic disturbances you would regularly see,” said Raphael Stern, a graduate research assistant at Vanderbilt University and a lead researcher on the study.
He said that these “phantom jams” are not actually mysterious at all. They are caused by people. As one driver hits the brakes or slows down, the vehicles behind them often make adjustments too aggressively.
This sets off a chain reaction that eventually leads to congestion.
“Humans are not perfect at driving,” said Daniel Work, associate professor of civil and environmental engineering at Vanderbilt, who led the study. “When traffic gets dense enough, small mistakes by one driver get amplified by the drivers behind them.”
Self-driving features help by ensuring automobiles move at a constant speed. “The idea is that the cars with self-driving features smooth out the flow by driving at the average speed,” Work said. “Simply put, when the cars ahead are racing toward a traffic jam, you want to drive slightly slower.”
Backed by the National Science Foundation, the researchers involved in the study began looking for opportunities to improve mobility systems in 2016.
The team rented 21 passenger vehicles including sedans, SUVs and trucks, then arranged them on a circular track along with one car that was fully selfdriving enabled. A driver was behind the wheel of each.
“When all the vehicles were driven by humans, we would see these stop-andgo waves,” Stern said. “But when we activated the autonomous vehicle, the stop-and-go waves stabilized.”
The researchers officially published their findings in April.
Ford caught wind of it and wanted to add adaptive cruise control to the equation, partnering with the scientists to re-create the simulation using 36 random drivers, Ford vehicles and a closed test track. The results: Vehicles using adaptive cruise control reduced the impact of a braking event smoother than those without the activated technology.
Stern said that even though the study was in a controlled environment, motorists can expect to see “tangible benefits” in everyday driving situations.
In addition to fewer traffic jams, having self-driving cars on the road can reduce the total fuel consumption of all the vehicles driving through phantom waves by 40 percent, researchers said.
A National Science Foundation study reveals that having a single selfdriving car on the road can reduce congestion by influencing the traffic flow of at least 20 human-controlled automobiles around it.