The biggest mistake is to panic and try to release the stuck accelerator, wasting valuable time, warns Stephen Mead, assistant chief examiner at Britain's Institute of Advanced Motorists.
"Brake normally," he advises. "As you do, you will feel the engine pulling against the brakes. In a manual, as you apply the brakes, depress the clutch.
"In an automatic, move the gear level to neutral.
"The engine will start screaming at you but ignore it. As the car begins to slow down in control, indicate and manoeuvre carefully to a position of safety, hard brake and kill the engine.
"Most other drivers will read the 'body language' of the car and start to back off but if you have the presence of mind, turn the hazard lights on."
Failing all else, he says, you could turn the engine off when the car was still moving as long as you had enough momentum to move out of the way of other traffic. But he warns drivers not to remove the keys as it will lock the steering wheel.
"Do not use the hand- brake at speed. If you do so and turn, it will lock the wheels and send you into a fish-tail spin. If you need to use the handbrake, do so gently in accordance with with the speed and distance of the vehicles in front."