stopping distance

The minimum distance in which a vehicle can be brought to rest in an emergency from the moment that the driver notices danger ahead. Stopping distances of vehicles can be estimated by using the formula:

stopping distance = thinking distance + braking distance

The thinking distance is the time taken for the driver to react by applying the brakes of the vehicle. This is known as the reaction time, and is about 0.1–0.3 seconds. As a general rule the breaking distance becomes four times greater as the speed of the car is doubled.

As a rough guide, the above formula can be used to work out the stopping distances of vehicles travelling at different speeds. In real situations, the actual stopping distance depends on many other factors such as the conditions of the road, the mechanical condition of the vehicle, and the physical state and mental alertness of the driver.