Stopping distance and reaction time

The idea

Stopping distance = thinking distance + braking distance. Thinking distance depends on speed and the driver's reaction time, which is typically 0.2 s to 0.9 s and is increased by tiredness, drugs, alcohol and distractions. Braking distance increases with speed and is affected by wet or icy roads and worn brakes or tyres. For a given braking force, the greater the speed, the greater the braking distance.

1. Thinking distance = speed × reaction time.
2. Add the braking distance.
3. Sort each factor into thinking or braking.

Watch out Alcohol increases thinking distance, not braking distance; icy roads increase braking distance.