MARYSVILLE, Ohio — Jeaneen Parsons' husband steered their motorcycle to the ground seven years ago to avoid hitting a passenger whose cycle went down on a twisting mountain road in Kentucky.

The couple emerged from the accident with a few road burns and frazzled nerves. The passenger's leg was shattered.

Marifran Mattson lost part of her left leg when the motorcycle she was on was struck by a semitrailer in 2004 near Crawfordsville, Ind.

Pittsburgh Steelers quarterback Ben Roethlisberger was seriously injured June 12 when a car turned into the path of his motorcycle. Roethlisberger, who wasn't wearing a helmet, suffered a concussion, broken nose and jaw and damaged teeth.

As cyclist injuries and deaths increase, motorcycle makers are installing more safety features — making greater use of antilock brakes and adding air bags while stressing safe-rider education and use of helmets.

Some people wonder how effective air bags will be, how much of a market exists, and how much they would save cycle owners on insurance.

Honda Motor Co. added air bags in June to its fully loaded Gold Wing, an 860-pound touring bike designed for distance driving in comfort and made near this central Ohio city.

Yamaha Motor Corp., with U.S. headquarters in Cypress, Calif., is developing an air bag system and is using a scooter with air bags for research in Japan, according to the company's Web site.

"The motorcycle manufacturers are engaging in a lot of R&D in the area of ... some would call it safety, some would call it risk management," said Tom Lindsay, spokesman for the Pickerington, Ohio-based American Motorcyclist Association. "It's part of a trend."

The motorcycle industry posted $7.6 billion in sales of 725,000 on-highway bikes in 2004, up from about $4.7 billion and 471,000 bikes sold four years earlier.

Motorcycles accounted for 2 percent of all registered vehicles in 2004 but made up 9.4 percent of all highway deaths, nearly double the 5 percent in 1997, according to government statistics.

Honda's air bag system consists of crash sensors attached to the front fork of the motorcycle. The sensors detect rapid deceleration and send the information to a small on-board computer, which determines whether a crash is occurring.

The computer sends a signal to an inflator, which releases nitrogen gas to deploy the air bag, packed into a dashboard-like module in front of the driver. The process takes a fraction of a second.

The system is designed to keep the driver's body from hitting whatever the motorcycle hit and reduce the chances of the driver being thrown over the handlebars. It is not designed to protect from side or rear impacts or to protect passengers.

Honda began working on its air bag system in 1990 after determining that more than half of the motorcycle accidents that result in deaths or injuries occur when the front of the motorcycle strikes another vehicle or object.

Honda won't say how many air bag-equipped Gold Wings it plans to produce by the time the 2006 model year ends in late September, other than it will be a limited number. Last year, the 600 workers at the plant produced 60,524 motorcycles, including Gold Wings.

Parsons, 45, of Dayton, favors the idea of air bags and doesn't shrink at the added cost — about $1,500 on a $24,000 Gold Wing.

Mattson, associate professor of communications at Purdue University, where she is spearheading a motorcycle-safety campaign, also applauds Honda but said the air bags wouldn't help in many crashes, including the one she was in. And she worries that the air bags might cause riders to dispense with wearing helmets.

"I'm concerned this might send a false sense of security," she said.

Honda officials acknowledge that some people are going to question whether motorcycle air bags will be effective.

"But we've seen so many test videos — you become a believer," said Jan Gansheimer, senior manager of Honda's manufacturing/planning group.