MIT Study Shows Tailgating Causes “Phantom Traffic Jams”

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Tailgating is when someone drives too close to your rear bumper. It’s dangerous and annoying and now an MIT study is giving you one more reason to dislike tailgating. According to researchers, tailgating also causes phantom traffic jams.

Traffic jams happen for all kinds of reasons and most of the time you can figure out why you’re crawling down the highway. A typical rush hour, accidents, vehicle breakdowns, and police officers on the side of the road can all make traffic slow down and snarl. Those are the reasons we can see, but what about those times when traffic slows down and then clears for no apparent reason? That’s a phantom traffic jam and tailgating is often to blame.

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It doesn’t make sense at first because you’d think anyone tailgating, despite incurring the hatred of the driver ahead, would end up keeping traffic moving right along. Even if the driver in front is tempted to slow down out of spite, that’s still not why tailgating is a problem. It all has to do with everyone’s ability to modulate their speed without coming to a stop.

The MIT study claims we all manage the distance between cars the wrong way. Traditionally, we look only at the guy right in front of us. If the guy in front slows, then we all slow down, but if we’re too close because we’re tailgating, then we have to stop.

That moment when a tailgating car is forced to stop because there wasn’t enough space to simply slow down starts a chain reaction where everyone has to come to an abrupt stop. Behold, the phantom traffic jam in action.

MIT professor Berthold Horn says the solution is what he calls bilateral control. Instead of simply looking at the car ahead to manage your speed, using bilateral control involves considering the car directly behind you, too. Basically, you want to leave enough room for everyone to drive at a steady pace with even gaps and no one too close.

Sounds like a good idea and one that would work, but the chances of the whole world changing how they drive are slim. Horn acknowledges this problem and sees a solution coming through autonomous driving technology.

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As the technology in our cars continues to evolve allowing vehicle-to-vehicle communication, sensors could easily monitor distances and adjust speed to keep cars evenly spaced on our roads and reduce phantom traffic jams.

Until then, knowing tailgating could cause a traffic jam is yet another reason to avoid this unsafe practice.