Examkin

Question

Difficulty: MediumAdjusting Margins in Wet Weather

You are following another vehicle along an open road in steady rain. When checking your safety separation using a stationary roadside landmark, what is the minimum time gap you should allow between the vehicle ahead passing the landmark and your vehicle reaching it?

  1. A
    One second, provided your vehicle is fitted with an anti-lock braking system (ABS)
  2. B
    Two seconds, because thinking distance is unchanged by rainfall
  3. Four seconds, because overall stopping distances double on wet road surfacesAnswer
  4. D
    Ten seconds, which is the required safety gap whenever precipitation occurs

Answer

At least four seconds, because wet road conditions double the required stopping distance compared to dry tarmac.
Under wet conditions, water reduces the friction between the tyres and the road surface, causing braking distances to double. To maintain a safe safety margin, the Highway Code requires drivers to double the normal two-second separation rule to at least four seconds.

Step-by-Step Solution

1
Identify the standard baseline following distance under normal dry conditions.
In dry weather, drivers should maintain a minimum time gap of at least two seconds from the vehicle ahead.
The two-second rule provides adequate buffer time for driver reaction (thinking distance) and vehicle braking.
2
Determine the physical impact of rain and surface water on vehicle stopping distance.
Water reduces tyre adhesion, which doubles braking distance and increases total stopping distance significantly.
Lower friction between the road surface and tyre tread requires a larger safety margin to stop safely in an emergency.
3
Calculate the adjusted time gap required in wet weather.
Double the standard two-second gap to establish a minimum four-second following margin.
Doubling the separation time ensures the trailing driver has sufficient space to stop without colliding with the vehicle ahead.

Key Concept

Doubling separation distance and time gap in wet conditions
Estimated Time:1m 0s
Rate this question

Topics

Adjusting Margins in Wet Weather

More questions from this topic