The braking distance is the distance the car travels from when you first apply the brakes until the car comes to a complete stop.
The braking distance increases or decreases quadratically (to the power of 2) in relation to the speed. For example, if you double the speed, the braking distance will quadruple and if you halve the speed, the braking distance decreases to a quarter.
If the braking occurs in other than ideal conditions, the braking distance can be many times greater. For example, if the road is wet or if car's brakes or tyres are in poor condition.