By approximately how much does stopping distance increase on a wet road?

• A. It remains the same.
• B. About twice as long.
• C. About half as long.
• D. Three times as long.

Answer: (B)

On a wet road the grip between tyre and surface is reduced, especially for braking. Stopping distance is made up of thinking distance (time to react) and braking distance (time to stop once brakes are applied). Water on the road cuts braking efficiency, so the braking distance grows more than the thinking distance. As a result, the total stopping distance is roughly doubled compared with dry conditions. That’s why you’d need about twice as long to stop when it’s wet, and you should increase following distance accordingly. It isn’t unchanged, not halved, and not tripled.