Braking distance versus stopping distance
Braking distance starts when braking force is applied. Before that, the vehicle travels during the reaction interval. Total stopping distance is the sum of both distances. This model assumes a level road, constant deceleration μg and no brake-force buildup delay.
reaction = v × t; braking = v² ÷ (2 × μ × g); v = km/h ÷ 3.6
Example stopping from 60 km/h
At 60 km/h the vehicle travels at 16.67 m/s. A one-second reaction covers 16.67 m. With μ = 0.7, modeled braking distance is about 20.23 m and total stopping distance is 36.90 m. Doubling speed doubles reaction distance but quadruples braking distance in this model.
Why actual stopping distance can differ
Grip varies with road surface, water, ice, tires and temperature. Gradient, braking equipment, ABS and driver behavior also affect the outcome. This calculator illustrates a physical relationship; it does not establish a safe following distance or reconstruct crash speed from skid marks.