WASHINGTON, D.C. — About 120 people are killed and more than 6,000 injured each year by vehicles that back over them, according to the National Highway Traffic Safety Administration (NHTSA) in a report by the Associated Press on December 9. Safety advocates want NHTSA to study the issue more closely and consider a requirement that automakers include devices to warn drivers when something comes into their path as they back up. About 20 percent of 2005 model year vehicles offer cameras or sensors mounted on the back bumpers. The sensors beep warnings, and the cameras transmit images to screens on the dashboard or rearview mirror. Backup aids aren´t always marketed as safety devices, so they can be difficult for consumers to spot in brochures. For example, the Toyota Sienna minivan´s sensor is called “intuitive parking assist´´ and comes standard only on the luxury model. On the Lexus RX330 sport utility vehicle, a camera is included if owners buy a $6,790 DVD navigation package. Forty percent of RX330 owners bought the package last year, the company said. Twenty percent of 2005 vehicle models offer cameras or sensors as standard equipment or an option, according to www.Edmunds.com/, an independent research company, as reported by the Associated Press. About the same percentage of vehicles offered the devices in the 2003-model year, although the actual number of models with cameras has increased. Automakers offering sensors on at least some models include Audi, BMW, Buick, Cadillac, Chevrolet, Ford, Mercedes-Benz, Nissan, Porsche, Volkswagen and Volvo. Several companies sell cameras, which can be installed for around $1,000, and sensors, around $400 or less. HitchCam, a 5-year-old company based in Commerce, Calif., that sells both devices, has seen sales jump 43 percent in the last year, spokesman Roger Hooker said. NHTSA, which sets vehicle standards, is a long way from mandating cameras or sensors. Spokesman Rae Tyson said the agency believes the technology remains too expensive and may not always be reliable. "It´s a potential problem because it might lull people into thinking there´s nothing behind them when there might be," Tyson said.