- Roads, Vehicles & Traffic
Calculating stopping distances
- Year 5
- Year 6
Discuss the concepts of ‘stopping distance’, ‘reaction distance’ and ‘braking distance’ and the relationship between speed and stopping distance.
Using the worksheet ‘Calculating stopping distances’, have students work out the total stopping distance for each speed and enter it on the chart.
Take students out into the school ground to measure the different stopping distances.
Speed and stopping distances
- What could we mean by the term ‘stopping distance’?
- What could we mean by ‘reaction distance’?
- What could we mean by ‘braking distance’?
- Why are the reaction distances and the braking distances different for each speed example?
- What happens to the distances as speed increases?
- Why do you think this happens?
- What would you expect to happen to the stopping distances if it was raining, foggy or night time?
- What would happen to stopping distances if the tyres were in poor condition?
- Would there be any difference in the stopping distance of a small vehicle and a fully loaded truck or bus?
Information for teachers
Stopping distance is the total distance that a vehicle travels to come to a complete stop from the time the driver first decides to stop, including the reaction distance and the braking distance.
Reaction distance is the distance that a vehicle continues to travel while the driver thinks about and processes the information required to stop the vehicle.
Braking distance is the distance a vehicle continues to travel once the brakes are applied.
Speeding includes travelling above the speed limit as well as driving too fast for the conditions, and these are major contributors to both the number and severity of crashes. The lower the speed limit the more time the driver has to observe and react to the surrounding road environment, and their stopping distance is shorter.
As a vehicle's speed increases, so does the time it takes for the vehicle to come to a stop. Combined with the fact that the higher the speed, the greater the impact, it becomes clear how a small increase in speed can make a big difference in the seriousness of a crash.
It's not only drivers and passengers that are affected. In fact, other road users such as pedestrians, cyclists and motorcyclists are more vulnerable and therefore more susceptible to death or serious injury if struck by a moving vehicle.
Studies show that small increases in speed can have large increases in the level of injury or the likelihood of death. Equally though, small decreases in speed can significantly reduce the severity of injuries to the vulnerable human, or avoid the crash in the first place.
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