braking distance

Braking Distance

the distance traveled by a motor vehicle, train, or streetcar from the instant a braking device is applied until a complete stop is achieved. The total braking distance, or stopping distance, includes the distance traveled from the instant the driver or engineer perceives the need to stop until the brakes are applied. The braking distance is proportional to the square of the velocity, the brake response speed, the load on the wheels to which the braking action is applied, and the coefficient of adhesion between the wheels and the road or tracks; the total braking distance also depends on the reaction time of the driver or engineer. The state of the tire tread and the road surface also have a great effect on the braking distance of motor vehicles.

In the USSR, in accordance with the Road Traffic Rules, the maximum permissible braking distance for a road vehicle at a velocity of 30 km/hr on a dry, level, hard road surface is 7.2 m for passenger cars, 9.5–11 m for trucks, and 7.5–8.2 m for motorcycles. The calculated braking distances for trains are established in the Regulations for the Technical Operation of Railroads.

A. A. SABININ