Motorcyclists in a growing number of states are being allowed to go through red lights when sensors aren't able to detect they are there.

In May, South Carolina became the seventh state to give motorcyclists license to proceed with caution after stopping when the device that causes the light to change from red to green doesn't activate, according to Imre Szauter, government affairs manager for the American Motorcyclist Association.

North Carolina passed a similar law in 2007. Wisconsin (2006), Idaho (2006) Arkansas (2005), Tennessee (2003) and Minnesota (2002), all have passed laws the past six years, Szauter said. Bills have been introduced for the same purpose in Georgia, Missouri and Oklahoma, according to the National Conference of State Legislatures and the legislative websites for those states.

The Federal Highway Administration says such laws raise safety concerns, but biker groups that have lobbied for the change say they are common sense.

"We want to emphasize that the riders do this with safety and caution in mind," Szauter said. "If they truly are trapped at a light, this gives them an opportunity to safely proceed through that signal, because otherwise they don't really have much of a choice."

Doug Hecox, a spokesman for the Federal Highway Administration, said the states should try to find a technical solution to the problem.

"We don't necessarily think that empowering motorists to make up their own rules of the road is the safest or best approach," he said.

The traffic lights in question are controlled by devices buried under the road that operate similar to metal detectors, according to Hecox. Their sensitivity can be set to detect motorcycles, but the proper balance is difficult to adjust, he said.

California has chosen a technological solution. A law adopted last year requires that when new traffic-activated signals are installed, they be capable of detecting motorcycles and bicycles.

Motorcyclist Splatt Ratt of Palm Springs, Calif., a member of the board of directors of a motorcyclists advocacy group called American Bikers Aimed Toward Education, said that's not good enough. Replacing all the ineffective traffic-detection devices could take years, he said.

"The gist of the whole problem is I live in the stop-light capital of the world," he said.

Reb Richardson, a motorcyclist from Sumter, S.C., said he pushed his state's Legislature for three years to get the bill passed that Republican Gov. Mark Sanford signed last month. Richardson's efforts grew out of frustration over a traffic light at the intersection near his home.

"That light would never change," he said. "There's just not enough metal in motorcycles to detect them."

Some motorcyclists try to deal with the problem by motioning for a car behind them to pull forward to trip the signal, Richardson said. This puts the biker in danger, forcing the motorcyclist to move too far into the intersection, he said.

Scott Kauffman of Portland, Ore., says he has a solution. He has developed a magnetic device he calls the Green Light Trigger that straps onto the motorcycle and causes the traffic light to think a car is there, he said.

He's not worried about the changes in state law putting his company, Green Light, out of business. It's still better than running red lights, he said.

"You may not need it legally, but they need it from a safety standpoint," he said.

Barnett reports for The Greenville News in South Carolina

Enlarge By Justin Sullivan, Getty Images In May, South Carolina became the seventh state to give motorcyclists license to proceed with caution after stopping when the device that causes the light to change from red to green doesn't activate.