The Intersector: A Traffic Light That Knows When Bicycles Are Coming

It’s time for some intelligent design in our traffic management. A new device can change light times to make things safer for oncoming bikes, and more convenient for impatient drivers.

It’s a problem even in the most bike-friendly cities: cars move faster than bikes, which means cyclists are put in danger when traffic lights change. To cut down on the danger of deadly crashes, a handful of California cities, including Pleasanton, Redding, and Monterey, are installing the Intersector, a smart traffic signal that can differentiate between bikes and cars—and then times traffic light changes accordingly.

The Intersector uses a microwave radar gun that can calculate the speed and length of approaching objects, so it knows whether a bike or car is rolling up. The device then decides how long the light should stay green so that both cars and bikes have enough time to pass through. Cars get four seconds to roll through, while bikes get 14 seconds. If a cyclist pedals through a light that’s already green when they arrive, the Intersector tacks on an extra five seconds of green. If no cars are coming, it can shorten the length of a green light to let people needlessly waiting at a red go ahead sooner.

Check out the Intersector in action below:

It’s not that Pleasanton, Redding, and Monterey have a soft spot for cyclists. In 2008, California’s AB 1581 law required counties and cities begin to replace service traffic signals with ones that can sense cyclists and motorcyclists, according to Government Technology. All new traffic signals must have this capability as well.

Pleasanton also uses video camera detection and inductive loops—metal detectors placed in the ground that alert traffic signals when cyclists are coming. Neither of these techniques are as accurate as the Intersector, which may be the most reliable bike-detection device for traffic signals available.

At $4,000 to $5,000, the device isn’t cheap. But Pleasanton, at least, was able to buy its Intersectors with sales tax cash from California’s Transportation Development Act. And San Jose recently scored $1.5 million from the Metropolitan Transportation Commission to track down and install the best bicycle detection devices. If cyclists are lucky, the lessons learned from California’s experiment in bike detection will be applied elsewhere.

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  • Letlizknow

    Why does this person have 5 different toolbars on his IE browser? Not sure if I would trust this programmer after seeing that. You would think they know better...

  • Remco

     they are either by the roadside or on bike path's right where the bikers line up to cross the road. They are just on a pole and also handy to balance yourself with while waiting so you don't have to put your feet on the ground ;-)
    Here is a picture: http://i727.photobucket.com/al...

  • 2check

    This idea is different, though, adjusting the time of the light when it is still green to allow bikes enough time to clear the intersections, rather than simply allowing the bikes to begin first from a red light.

  • Remco

    They are over thinking the problem. Here in the Netherlands we are considered the biking capital of the world: everyone from the gardener to the heads of state use bikes to get place or go to work. And we fixed this problem - long ago - all a biker has to do is push a little button either on the main road or on the bike path. The system knows there is a bike and adjusts accordingly.

    It's effective and a lot cheaper!

  • cia

    @Remco, where is that button on the main road? On a pole? Or where is it on the bike path? I'd love to see a photo of it! Just curious.