MnDOT pilot project in Northfield gives bikes the green light

Many cities now give bicyclists their own lane, but the technology that grants them a green light at intersections has lagged.

A Minnesota Department of Transportation (MnDOT) pilot project in Northfield is testing a new traffic signal sensor that uses radar to detect when a bike is approaching the intersection, triggering a green light and 10 seconds to get across.

"We're getting a lot more requests for bicycle detection at signals" from cities, counties and individuals, said Jerry Kotzenmacher, MnDOT's traffic system specialist. "It seems to be something big across the whole country."

The sensor was installed at Hwy. 3 and 2nd Street three weeks ago and has worked well so far, said Kotzenmacher, though he wants to try it in different weather conditions and over a longer time period.

The project meets a Northfield need, providing a way to safely get across Hwy. 3, a busy road that separates the east and west sides of town as well as Carleton and St. Olaf, Northfield's two colleges, said Erica Zweifel, a City Council member and biking enthusiast.

Without a detection system — or one that works consistently — bicyclists are sometimes forced to run red lights or bike onto the curb to push the pedestrian button to cross the street, Zweifel said.

It's dangerous, she said, and when the pedestrian button is pushed, cars sit for a lengthy 35 seconds, frustrating drivers.

In other cities, efforts to detect bicycles using various methods have had mixed outcomes, Kotzenmacher said.

But Minneapolis is using traditional vehicle sensors and video detectors with good results, said Steve Mosing, traffic operations engineer for the city of Minneapolis.

Minneapolis also offers buttons bikers can push — similar to pedestrian buttons but close to the curb so bikers don't have to get off their bikes — to get a green light at some intersections.

"This is MnDOT's first attempt at putting in a detector like this, specific to a traffic signal," Kotzenmacher said. "I would like to say MnDOT is leading the effort, to a certain degree."

Radar, video and thermal energy have all been used to identify bikes at intersections, said Nick Mason, deputy director of the Bicycle Alliance of Minnesota, and methods are becoming more sophisticated and effective.

MS Sedco, an Indianapolis company, makes the equipment MnDOT is piloting. Kotzenmacher was skeptical it would work, so the company donated it, putting "their money where their mouth is," he said.

The system uses radar to pick up a moving image within a 30-foot zone and can distinguish a bicycle from people and cars. Once detected, the light turns green — or a green arrow appears for a left turn — and the bike gets 9.5 seconds to cross, Kotzenmacher said.

The cost is about $5,000 per approach, or $10,000 total for most intersections, Kotzenmacher said.

If the project is successful, MnDOT may implement it more widely, he said.

Zweifel has tried the new sensor at least twice a day while biking to work at Carleton. Once, it didn't work, but it's been effective every other time, she said.

Erin Adler • 612-673-1781