Stopping distance for cars
Many drivers have a false belief that if the car in front starts braking, they can react, brake and come to a stop, still leaving the same distance between the two vehicles.
The total minimum stopping distance of your vehicle depends on four things:
- your perception time,
your reaction time, your vehicle reaction time, and your vehicle braking capability.
Your perception time is how long it takes you to see a hazard and for your brain to realise it is a hazard requiring you to take immediate action. This can be as long as 0.25 to 0.5 of a second.
Your reaction time is how long you take to move your foot from the accelerator to the brake pedal once your brain understands you are in danger. Your reaction time can vary from 0.25 to 0.75 of a second or more. It can be as long as 1.5 seconds.
These first two components of stopping distance are down to you, and they can be affected by alcohol, drugs, tiredness, fatigue or lack of concentration. A perception and reaction time of 4 seconds at 100kmh means the car travels 110 metres before the brakes are applied (this is more than the length of a football pitch).