Driving faster not only lessens drivers’ chances of being able to stop in time to avoid hitting someone or something. It also means if they can’t stop in time, they will hit with greater impact. The greater the impact, the greater the chances of causing serious injury or death.
A vehicle travelling at 20mph (32km/h) would stop in time to avoid a child running out three car-lengths in front. The same vehicle travelling at 25mph (40km/h) would not be able to stop in time, and would hit the child at 18mph (29km/h). This is roughly the same impact as a child falling from an upstairs window.
The greater the impact speed, the greater the chance of death. A pedestrian hit at 30mph has a very significant (one in five) chance of being killed. This rises significantly to a one in three chance if they are hit at 35mph. Even small increases in speed can lead to an increase in impact severity.
Brake the Road Safety Charity