Hugh Borbidge, BSME, Director of Engineering Animations
We, as vehicle operators, avoid collisions every day. We stop for red lights, brake when a car cuts us off, and slow down if there are children playing close to the roadway. In these avoidance situations, there are three components: Perception, reaction and braking.
Perception is when we first notice a hazard or the need to react to something. Reaction is the time taken to respond to what was perceived. A typical daytime perception/reaction time for a vehicle operator is about 1.5 seconds, meaning that, when you notice a hazard you keep traveling at the same speed for 1.5 seconds before you start applying the brakes. Braking is the minimum time it takes to bring the vehicle to a stop. Every bit of time in this series of events equates to a certain distance traveled. For example: