Professor discovers the cause of the phantom traffic jam

One of the must frustrating hangups on the road is the phantom traffic jam. It can be a perfectly clear summer day, dry roads, no accidents, and yet the cars just suddenly bunch up and come to a stop for no apparent reason.

But there is a reason.

“If there are enough cars on the road something very minor can get magnified into a traffic jam,” Dr. Eddie Wilson said.

The right way to zipper merge

Wilson, a professor of engineering at Bristol University in the UK, had 22 drivers drive around a circular track with orders to keep a steady speed of 15 mph.

“Everyone’s going to try and drive the same speed, but driving behavior is not perfect,” he said. “Some people go a little bit faster, some people go a bit slower, and traffic will start to bunch up.”

Even with no obstructions traffic bunches up and looks like a circular caterpillar until, eventually, some of the cars have to stop.

And the culprit was the one guy who went just a little too fast, and then had to tap the brakes. That first brake tap then ripples down the line with each car slowing a little bit more, until traffic stops.

So here’s the rule: never make it necessary for you or anyone else to tap the brakes.

“If you see space open up in front of you, don’t rush to fill it,” Wilson said.

The second rule, he says, is if you’re in a traffic jam and the other lanes seem to be moving faster, don’t change lanes.

“If you change lane you just make the traffic flow worse,” he said.

I know, two pieces of advice that nobody is going to follow. But I was hoping that if it came from a professor with an English accent and if everyone reads this before their next commute, I might just help you arrive a few minutes faster.

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