When you are sitting at a traffic light, this is what’s happening. A control system for the lights is counting down the seconds before your light changes from red to green. You’re essentially waiting on a clock to tick down. Before you arrived at that intersection, traffic flow was analyzed, numbers crunched, and the lights were set according to an “optimal” schedule, depending on where and when you’re driving.

As anyone can attest, this doesn’t always work out. Sometimes you’re the only person waiting at this particular intersection, or it could be packed, bumper to bumper. The problem according to Dirk Helbing and Stefan Lammer, two scientists studying ways to improve traffic congestion, was that “the average situation never occurs.”

One of the ways they recognized this problem and the potential solution speaks to the value in bottom up approaches to solving problems, which often begin with simple ethnography:

They noted that when crowds of people are trying to move through a narrow space, such as through a door connecting two hallways, there’s a natural oscillation: A mass of people from one side will move through the door while the other people wait, then suddenly the flow switches direction.

“It looks like maybe there’s a traffic light, but there’s not. It’s actually the buildup of pressure on the side where people have to wait that eventually turns the flow direction,” says Helbing. “We thought we could maybe apply the same principle to intersections, that is, the traffic flow controls the traffic light rather than the other way around.”

Based on their research, Helbing and Lammer are instead developing a system that takes a bottom up approach to managing traffic lights. Their system places two sensors at each intersection to measure traffic flow in and out. Each intersection then communicates with the next to prepare for incoming traffic. Gaps are opportunities for the opposite flow to have their turn.

Lights respond to cars, not the other way around.

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