Thinking Distance

The thinking distance is the distance a vehicle travels during the driver's reaction time, from the moment the driver sees a hazard to the moment the brakes are applied.During this time the vehicle is assumed to be moving at constant speed, so thinking distance = speed × reaction time, s = vt₀. The thinking distance is therefore directly proportional to the speed: doubling the speed doubles the thinking distance.A typical reaction time is a few tenths of a second. For a car travelling at 18 m s^-1 with a reaction time of 0.3 s, the thinking distance is 18 × 0.3 = 5.4 m.Anything that slows down the driver's reactions increases the thinking distance. Examples include tiredness, alcohol, drugs and distractions such as using a phone.Road and vehicle conditions, such as wet roads or worn tyres, do not affect the thinking distance. They affect the braking distance, which is added to the thinking distance to give the total stopping distance.