5.8.4 Factors Affecting Thinking Distance & Reaction Time

Speed and Stopping Distances

As the vehicle speeds up, the thinking distance increases at the same rate as the speed. This is because your reaction time doesn't really change, but the speed you are going does. So the higher the speed, the more distance will be travelled during your reaction time.

As the vehicle speeds up, the braking distance increases. This is because as there is more speed, there is more kinetic energy due to $KE = \frac{1}{2}mv^2$. Therefore, as the speed increases, the kinetic energy increases at a higher rate. This means more work needs to be done to transfer the kinetic energy, so more distance is required as long as the braking force is constant $(W=Fs)$.

Stopping distance against speed graphs

We can use these graphs to compare different vehicles and their different stopping distances. If you wanted to find out which vehicle had a shorter stopping distance at a certain speed, this can be read off the graph and then compared: