Stopping distance is dependent on two factors: Breaking distance and Thinking distance. Braking distance is the distance the car travels during its deceleration while the brakes are being applied, while thinking distance is the time it takes for a driver to activate the brakes or situation. There are many factors that increase stopping distance such as greater speed, poor road conditions and car conditions. On the other hand, factors that affect thinking distance are tiredness, alcohol and drugs, distractions, and tiredness.
The diagram shows that thinking distance and braking distance depends on the speed of the car. It also shows that stopping distance is much further for faster speeds. As the speed increases, so does the likelihood of a pedestrian being killed during a collision. This is the reason why drivers should keep to the speed limit and add a 3 second distance to the car you are following during normal conditions while doubling it during wet/slippery conditions.