WASHINGTON -- Concern over the implications of a 2006 revision to a federal safety standard is spurring regulators at the National Highway Traffic Safety Administration to review if the change, which redefined what constitutes a car's ignition key, raises the potential for accidents caused by a vehicle rolling away.
The matter involves the so-called smart-key fobs used in millions of vehicles to replace conventional metal keys. Instead of pins and tumblers, the devices use an electronic code that enables a vehicle to be started either by pressing a button or inserting the fob into a slot on the dashboard.
But under the revised agency standard for such devices, the vehicle's engine can be shut off and the key fob removed without the automatic transmission shifted to the "Park" position.
A safety agency spokesman, Jose Alberto Ucles, said in an e-mail exchange that the chief concerns behind the review "are vehicle roll-away, theft, possible carbon monoxide poisoning, and shutting off moving vehicles in the event of an emergency."
A federal regulation in place since 1992 requires automakers to prevent the removal of a key from the ignition unless the transmission is in Park, a measure intended to prevent the "accidental roll-away of motor vehicles."
But as electronic fobs became more popular, the agency expanded its definition of the key to include the electronic codes of smart fobs.
In late August, 2008, after she parked her 2009 Nissan Murano on a slight incline, Jeanette Taylor, 67, of Washington Parish, Louisiana, got out of the vehicle to retrieve a package from the back seat.
"I thought it was rolling a little bit and then I thought … I was just imagining things," she said. "There is no way it could move."
Ms. Taylor said she assumed the vehicle had to be in "Park" for her to remove the key. But when the Murano began to speed up, she opened the driver's door and tried to climb in.
"But it knocked me down," she said in an interview. "I was afraid if I didn't grab something, it would pull me under the car."
She was dragged into the street. A passer-by jumped into the vehicle and stopped it, but the tire stopped on her leg, causing serious injury.
David Champion, director of the Consumers Union auto test center, checked 11 vehicles purchased by Consumer Reports magazine for testing. Mr. Champion said that seven, including 2010 and 2011 models from Hyundai, Infiniti, and Lincoln, allowed the engine to be turned off with the gearshift lever in Neutral or Drive.
But because of audible and electronic warnings, Mr. Champion said, he did not see this as "too much of an issue." In e-mails, spokesmen for Hyundai Motor Co., Nissan Motor Co. Ltd. (Infiniti's parent) and Ford Motor Co. said their vehicles complied with federal standards.