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S is for Stopping Distance

  • Thinking distance
  • Braking distance
  • Overall stopping distance

Let’s say you are driving past a school at 30 mph. A child runs out in to the road 10 metres ahead. How fast will you be travelling when you hit the child? You’ll need some extra information to work out an accurate answer, but have a guess…

Here comes another snippet of information: the overall stopping distance at 30 mph is 23 metres. Do you want to change your answer?

And another snippet of information: the thinking distance at 30 mph is about 9 metres (remember the child you are about to hit is only 10 metres away). Have another think about your answer.

Using official Highway Code figures for braking distance and Department of Transport figures for reaction time (thinking distance) you will still be travelling at about 27 mph when you hit the child. At 40 mph you won’t even have time to reach the brake pedal before hitting the child.

At 20 mph you will hit the child at about 7 mph. Not acceptable, but the child will probably walk away with bruises. Driving near a school or playground? Twenty is Plenty

Thinking distance + braking distance = stopping distance
(Figures assume ideal conditions)