Chapter two icon left

Stopping distance

 

The total stopping distance to bring a vehicle to a complete stop is measured from the time a driver realizes the need to apply the brakes until the vehicle comes to a full stop. The time it takes for a vehicle to stop is affected by four factors.

  1. Perception time is the amount of time it takes a person to realize the need to stop the vehicle. The average perception time is about three-quarters of a second. Perception time can increase if a person is not paying attention to driving, or is not feeling well physically or mentally. 

Perception distance is how far a vehicle travels during this time.

  1. Driver reaction time is the amount of time it takes between deciding to stop and actually applying pressure to the brake pedal. Normal driver reaction time is about three-quarters of a second. Reaction time will be slower if the driver:

  • is tired, or 

  • has been drinking alcohol or using drugs.

Reaction distance is how far a vehicle travels during this time.

  1. Lag time is the amount of time it takes for the air brake system to respond after the driver has applied pressure on the brake pedal. Air brakes do not respond immediately because it takes time for the compressed air to flow through the system and apply the brakes. 

Lag time distance is how far a vehicle travels during this time.

 


Page 56