Stopping time and distance (continued)
Reaction time
Reaction time is how long it takes to respond to a situation by moving your foot from the accelerator pedal to the brake pedal. The average reaction time is three-quarters of a second. Reaction distance is how far a vehicle travels during this time.
Braking time
Braking time is how long it takes a vehicle to stop after the brakes are applied. Braking distance is how far the vehicle travels during this time.
Perception distance + Reaction distance + Braking distance = Total stopping distance
The chart below illustrates the minimum stopping distance for various speeds. The stopping distances are averages for stopping on smooth, dry pavement. 110 km/h 100 km/h 80 km/h 50 km/h 30 km/h Distance travelled while perceiving the need to stop (based on an average perception time of ¾ second) Distance travelled while reacting (based on an average reaction time of ¾ second) Distance travelled after brakes applied (under normal road conditions and brake efficiency) Many factors affect your stopping time and distance. These include road and weather conditions. Some factors you can control are:
- your visual search skills as you scan the roadway ahead
- your decision-making ability
- your alertness and level of fatigue
- your use of alcohol or drugs
- your vehicle’s speed
- the condition of your vehicle’s brakes and tires.
Braking
- When stopping, begin braking early. If you brake too late, your braking distance may not be sufficient.
- Release pressure on the accelerator before applying the brake to reduce your speed.
- To finish braking smoothly, release pressure on the brake pedal slightly and then reapply pressure on the pedal just before you come to a stop.
- If you must stop quickly, use threshold braking. This is applying the brakes without locking the wheels. This is where braking efficiency is at its maximum while still allowing you to steer your vehicle. If the wheels lock, release your pressure on the brake pedal slightly. Applying the brakes hard enough to lock the wheels will cause a loss of steering control. For vehicles with anti-lock brakes (ABS), see information in Chapter 6 under emergency braking.