The National Highway Traffic Safety Administration has closed its probe into claims that three Ford sport utility vehicles from the 2002 to 2005 model years can roll away when the transmissions are in park. Federal officials the failure rates were too low to warrant recalls.
The NHTSA probe, which began nearly four years ago, involved about 1.5 million Ford Explorer, Mercury Mountaineer and Lincoln Aviator SUVs.
There had been 36 complaints, including 14 linked to crashes and six to injuries.
Federal investigators said they found that the parking gear in the transmission failed 4.4 times per 100,000 vehicles.
A system that stops the SUV from being shifted into gear unless the driver's foot is firmly on the brake pedal failed only 3.4 times per 100,000 SUVs, they said.
"For all identified failure mechanisms," NHTSA documents related to the probe said, "there has been a drastically declining trend, including very few incidents occurring in recent years. Accordingly, this investigation is closed."