The success of anti-lock brakes in preventing accidents apparently depends on drivers breaking old habits.

Two studies released Wednesday concluded that many drivers might not be familiar with how to use the brakes properly. Anti-lock brakes should not be pumped. Drivers traditionally have been taught to pump."We want to remind people that when they step on the brake, you want to push down hard and keep the pedal pushed down," said Ricardo Martinez, head of the National Highway Traffic Safety Administration, which released one of the studies.

Anti-lock brake systems are designed to prevent a vehicle's wheels from locking to give drivers better control and decrease stopping distance during emergency braking on slippery roads.

When the anti-lock brakes engage, the driver won't hear the brakes squeal but will feel the pedal vibrating.

That's because the system is working by pumping the brakes faster than is humanly possible, Martinez said.

"But if you're not familiar with the system, you may think it's not working and take your foot off the pedal or turn to overcorrect," he said.