What's causing this traffic jam? If you tailgate, it's caused by someone like you

Perhaps you're one of them — someone who, in the rush to get from points A to B, instinctively creeps up on the rear bumper of the cars or trucks ahead of you, one after another, until they either switch lanes and allow you to pass or speed up themselves. Or maybe it just seems inevitable in heavy traffic. But a new report suggests that such tailgating is actually a big cause for "phantom traffic jams" that arise seemingly out of nowhere.

Researchers from MIT's Computer Science and Artificial Intelligence Laboratory in a new journal article say that maintaining an equal distance between cars in front of and behind you could allow drivers to get where they're going twice as quickly. They call the approach "bilateral control" and base it in part on observations of how starling birds fly together in tandem.

"We humans tend to view the world in terms of what's ahead of us, both literally and conceptually, so it might seem counterintuitive to look backwards," says MIT professor Berthold Horn, who co-authored the article in IEEE Transactions on Intelligent Transportation Systems. "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."

Of course, human nature is tough to change, and conditions on roads will always be unpredictable and prompt interruptions in the flow of traffic by individual cars, which the researchers call "perturbations." So the researchers suggest that car companies update their adaptive cruise-control systems by adding front and rear sensors (most only employ a front-bumper sensor). It's similar to a system Honda began developing years ago, and Horn plans to do work funded in part by Toyota to test whether this method would help traffic move more quickly but also more safely for drivers.

That approach, rather than requiring a massive coordinated network of connected vehicles, would simply require new software and some inexpensive hardware upgrades. "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," Horn says.

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