A sea of green lights

Should signals follow traffic, not vice versa?

Stephen Studd/Getty Images

Brakes squealing, horns honking—traffic congestion is a huge problem, and it’s only getting bigger. But researchers with the Santa Fe Institute, a non-profit think tank that examines complex systems, are working to alleviate the smoky urban gridlock. The institute recently released a study proposing a new way to reduce road congestion: changing how traffic lights work. Currently most signals are on timers programmed to turn green or red according to the expected number of vehicles passing through intersections at certain times throughout the day—a system, scientists say, that’s due for an upgrade.

“Because of the large variability in the number of cars behind each red light, it means that although we have an optimal scheme, it’s optimal for a situation that does not occur,” Dirk Helbing, external professor with the Santa Fe Institute and co-author of the study, told Wired magazine. He proposes a new system, where signals respond to traffic instead of attempting to control it. This is accomplished by placing sensors at intersections to measure incoming and outgoing cars and alert other signals when a large volume is coming. The lights change once a certain number of vehicles pile up, creating a small local flow through several intersections that speeds up traffic globally and allows lots of cars to move through a string of green lights.

A simulation in Dresden, Germany, had traffic delays for trams and buses falling by more than half, while pedestrians and cars saw declines in wait times of 36 and nine per cent. Cities such as Dresden and Zurich are now considering implementing the system, and all that’s left is to see if it works on the large scale, or if it will become another nuisance set to leave commuters stranded before a series of red lights.

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