Stopping Distances

Define the term 'stopping distance'.


The minimum distance required to stop a vehicle in an emergency

What is the equation for stopping distance?


Total stopping distance = thinking distance + braking distance

Define the term 'thinking distance'.


How far a car travels during the driver's reaction time (time between the driver seeing the hazard and applying the brakes)

What are the 2 things that affect thinking distance?


• Speed

• Reaction time

Explain how speed affects thinking distance.


The faster you're going, the further you'll travel in the time that you have to react

Explain how reaction time can affect thinking distance.


Anything that decreases alertness (e.g. being drunk, on drugs, tired, or distracted) will increase reaction time and therefore increase thinking distance

Define the term 'braking distance'.


Distance taken to stop under the braking force (distance taken to stop, once the brakes are applied)

What are the 4 factors that affect braking distance?

• Speed

• Weather or road surface

• Quality of brakes

• Condition of tyres

Explain how speed can affect braking distance.


The faster a vehicle travels, the longer it takes to stop

Explain how weather or road surface can affect braking distance.


If it is wet or icy or there are leaves or oil on the road, there is less grip (as so less friction) between the vehicles tyre's and the road, which can cause the tyres to skid

Explain how the quality of brakes can affect braking distance.

If brakes are worn out or faulty, they won't be able to apply as much force as well-maintained brakes

Explain how the condition of tyres can affect braking distance.



If the tyres of of a vehicle are bald (they do not have any tread left) there will be less friction between the tyres and the road, causing the tyres to skid

Why are speed limits important?

Because speed has a large effect on braking distance - when speed increases, braking distance increases by a factor of 2 (squared)