A vehicle is travelling at a constant speed of 70 mph on a motorway during rainfall with surface water present. Under standard dry conditions at this speed, the Highway Code establishes a thinking distance of 21 metres and a braking distance of 75 metres. In wet conditions, the distance required to brake to a complete stop doubles, while driver reaction time and thinking distance remain unchanged. What is the total stopping distance, in metres, required for the vehicle to stop safely under these wet conditions?
Answer: 171 metres
Answer
171 metres
Under wet road conditions, tyre friction is significantly diminished, which doubles the distance covered once the brakes are applied from 75 metres to 150 metres. Because the vehicle's speed is unchanged and driver reaction time remains standard, thinking distance remains 21 metres. Combining the 21 metres of thinking distance with the 150 metres of wet braking distance results in a total stopping distance of 171 metres.
Step-by-Step Solution
Key Concept
In wet weather, braking distance doubles due to reduced tyre friction, while thinking distance remains unaffected at the same speed.
Estimated Time:1m 30s