What is the stopping distance at 30 mph?

• A. 12 metres
• B. 36 metres
• C. 53 metres
• D. 23 metres

Answer: (D)

Stopping distance is the sum of thinking distance and braking distance. Thinking distance is how far you travel from the moment you decide to brake until you actually apply the brakes, and braking distance is how far you travel from you start braking to when you stop.

For a typical dry road at 30 mph, the common estimates are about 9 metres for thinking distance and about 14 metres for braking distance. Add them and you get roughly 23 metres in total. So 23 metres is the best fit for the stopping distance at 30 mph.

Keep in mind that conditions and driver reaction time affect this. Wet, icy, or poorly maintained roads, or a longer reaction time, will increase the stopping distance beyond the rough 23-metre figure.