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Common theory questions

How do you calculate the stopping distance?

You calculate the stopping distance by adding the reaction distance and the braking distance (reaction distance + braking distance = stopping distance).

The stopping distance is the entire distance the car travels from when you discover an obstacle or a hazard until the car comes to a complete stop. The stopping distance is made up of two parts: a reaction distance and a braking distance.

Stopping distances in ideal conditions:

  • 30 km/h: 9 + 4.5 = 13.5 metres
  • 50 km/h: 15 + 12.5 = 27.5 metres
  • 70 km/h: 21 + 24.5 = 45.5 metres
  • 90 km/h: 27 + 40.5 = 67.5 metres
  • 110 km/h: 33 + 60.5 = 93.5 metres

If the reaction time is longer than the average (one second) and/or if the braking occurs in other than ideal conditions, the stopping distance can be many times greater.