Tailgating insights untangle torment of phantom traffic jams

Specifically, the team argues that if motorists kept an equal distance between the cars in front of and behind - an approach that MIT professor Berthold Horn describes as “bilateral control” – then journey times would improve thanks to fewer phantom traffic jams, which occur for no obvious reason.

“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 Horn, who co-authored a paper on the subject of traffic congestion with postdoctoral associate Liang Wang. “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.”

According to MIT, Horn understands that drivers themselves are unlikely to change their forward-looking ways anytime soon, so he suggests that car companies update their adaptive cruise-control systems and add sensors to both their front and rear bumpers.

According to Horn, traffic would get noticeably better even if just a small percentage of all cars were outfitted with such systems. In future work part-funded by Toyota, he plans to do simulations to test whether this method is not just faster for drivers, but also safer.

According to the CSAIL team, for decades there have been hundreds of academic papers looking at the problem of traffic flow, but very few about how to actually solve it.

One proposed approach is to electronically connect vehicles together to coordinate their distances between each other. But so-called “platooning” methods require detailed coordination and a massive network of connected vehicles. In contrast, the CSAIL team’s approach would simply require new software and some inexpensive hardware updates.

Horn first proposed the concept of “bilateral control” in 2013 at the level of a single car and the cars directly surrounding it. With the new paper, he has taken a more macro-level view, looking at the density of entire main road systems and how miles of traffic patterns can be affected by individual cars changing speeds, which his team refers 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.

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