Have you ever been stuck in a traffic jam and assumed there was an accident ahead, only to discover it had no apparent cause? According to a new study, these “phantom traffic jams” could be greatly reduced in number if we’d all do one thing: stop tailgating.
Specifically, the researchers say that if we all kept an equal distance between the cars in front of and behind us — an approach known as “bilateral control” — we would all get where we’re going almost twice as quickly.
“We humans tend to view the world in terms of what’s ahead of us, both literally and conceptually, so it might seem counter-intuitive to look backwards,” said Dr. Berthold Horn from the Computer Science and Artificial Intelligence Laboratory (CSAIL) at the Massachusetts Institute of Technology (MIT).
“But driving like this could have a dramatic effect in reducing travel time and fuel consumption without having to build more roads or make other changes to infrastructure.”
Horn, who co-authored the study with postdoctoral associate Liang Wang, acknowledges that drivers themselves are unlikely to change their forward-looking ways anytime soon, so he suggests that car companies would do well to update their adaptive cruise-control systems by adding sensors to both their front and rear bumpers. (Most of today’s systems only have front sensors.)
In fact, traffic would get noticeably better even if just a small percentage of all cars had such systems, he says. In future work funded in part by Toyota, Horn plans to test whether this method is not just faster for drivers, but also safer.
The research has been inspired in part by how flocks of starling birds move in tandem.
“Birds have been doing this for centuries,” says Horn. “To program this behavior, you’d want to look at the birds all around you and not just the ones in front of you.”
According to the CSAIL team, for decades there have been hundreds of academic papers detailing the problem of traffic flow, but very few have figured out how to actually solve it.
Horn first proposed the concept of “bilateral control” in 2013 at the level of a single car and the cars directly surrounding it. In the new paper, he takes a more macro-level view, looking at the density of entire highways and how miles of traffic patterns can be affected by individual cars changing speeds (referred to as “perturbations”).
“Our work shows that, if drivers all keep an equal distance between the cars on either side of them, such ‘perturbations’ would disappear as they travel down a line of traffic, rather than amplify to create a traffic jam,” says Horn.
The new findings are published in the journal IEEE Transactions on Intelligent Transportation Systems.