Stopping Distances

The stopping distance is the distance covered from the moment the driver notices a danger to when the car comes to a complete stop. This includes the thinking distance and the braking distance. So:

Stopping distance = Thinking distance + Braking distance

Thinking distance

Thinking distance is the distance the vehicle travels during the driver’s reaction time. The reaction time is the time between when the driver sees the hazard and when they apply the brakes.

Speed affects the thinking distance. The faster the vehicle is travelling, the further it will travel during the driver’s reaction time. This increases the thinking distance. Therefore, if the vehicle is moving faster, it requires a longer distance to come to a stop, even if the same braking force is applied.

Although reaction times vary among individuals, an increased reaction time leads to a longer thinking distance. The following factors increase the driver’s reaction time: The following factors can increase a driver’s reaction time:

  • tired
  • drunk or under the influence of other drugs
  • distracted

Braking distance

The braking distance is the distance a car travels from the moment the driver applies the brakes to when it comes to a complete stop. The factors that can affect the braking distance are:

  • The mass of the vehicle – A heavier vehicle will take longer to stop.
  • The condition of the road – For example, wet roads make it harder to slow down (decelerate).
  • The vehicle’s condition – Factors like bad brakes and worn tyres can affect stopping.

When the brakes are used, work is done by the frictional force between the brakes and the wheels. This reduces the kinetic energy of the vehicle, transferring it to the brakes. As the car’s kinetic energy decreases, the thermal energy of the brakes increases, causing them to heat up.

A larger braking force is needed to stop a vehicle that is travelling at high speed. However, this can overheat the brakes because more kinetic energy is transferred to thermal energy. A larger braking force can also cause the driver to lose control of the vehicle.

You’ve used 10 of your 10 free revision notes for the month

Sign up to get unlimited access to revision notes, quizzes, audio lessons and more

Sign up