The National Highway Traffic Safety Administration proposed on Thursday to change accelerator testing standards for most new cars and many trucks and buses. The override systems, which activate automatically when the accelerator and brake are pressed simultaneously, would be required in passenger cars, trucks and buses weighing less than 10,000 pounds.
Many vehicles are already equipped with such brake-throttle override systems.
The proposal comes nearly three years after an investigation of unintended acceleration in some Toyota models, including a high-speed crash near San Diego that killed four people.
Federal investigators found no electronic defects, but they also found that in some cases, drivers had inadvertently pressed the brake and gas pedal at the same time or that gas pedals had become trapped.
In the San Diego case, investigators determined that the driver, a veteran California highway patrolman, had applied the brake of the loaned car but was unable to override the accelerator, which was trapped by a floor mat.
In February 2011, Toyota Motor Corp. recalled 2.17 million vehicles in the United States to address accelerator pedals that could become trapped in floor mats or jammed in driver's-side carpeting, prompting the NHTSA to close its investigation. The agency also fined Toyota $50 million for not recalling millions of vehicles in a timely fashion.
The goal of NHTSA's proposed standard is to minimize the risk that drivers will lose control of their vehicles as a result of either accelerator-control system disconnections or accelerator-pedal sticking or floor-mat entrapment.
However, safety experts say the proposal doesn't address the larger issue of drivers who mistakenly press down on the accelerator when they mean to apply the brake.
NHTSA has been working on regulations to address the placement of gas pedals relative to brakes to prevent such mistakes, but there has been no indication when a proposal might be offered, said Clarence Ditlow, the executive director of the Center for Automotive Safety.
NHTSA's 129-page proposal gives automakers about three years before the requirement for brake-throttle override systems kicks in. The public has 60 days to comment on the proposal.
The Associated Press contributed to this report.