Contains the full lesson along with a supporting toolkit, including teachers’ notes.
Every year some hundreds of people are killed on the roads in Ireland – about one a day on average. Awareness campaigns have not produced the desired change in driver behaviour. An understanding of the factors that are common to many road accidents and an understanding of the laws of motion may help increase awareness of the dangers and encourage young people to take greater care on the road whether as pedestrians, cyclists, passengers or drivers.
Reaction time (normal reaction time)
The average time for reaction to visual stimuli (with no choices) is between 180 and 200 ms (0.18–0.20 s). In the case of auditory stimuli it is shorter (140–160 ms). When decisions are required the time required to make an appropriate response to a visual stimulus increases with age from about 370 ms, for 20–30 year olds, to about 440 ms for 60–70 year olds.
Other factors that affect reaction time are:
Many studies have shown that 95% of real response times of drivers are in the range 1.5 to 2.5 seconds; the faster responses were recorded when drivers were warned that there might be a hazard and were therefore in a state of readiness.
Speed and braking distance
The stopping distance for a car depends on driver reaction time, the speed of the car, the slope and condition of the road surface, the condition of the tyres and the brake system of the car. In bringing a car to rest its kinetic energy must be dissipated in some way; ideally it generates heat in the brakes. If the brakes are applied so hard that the wheels cannot turn then the car skids and frictional energy is dissipated in the tyres and the road; when this happens the car cannot be steered and the stopping distanceincreases.