Determining Stopping Distance

Topic Progress:
  • Time and Distances

    Total Stopping Time is the entire time from the moment a hazard appears to when you bring your vehicle to a complete stop.
    Subdivides into Perception Time the time it takes for you to spot the danger
    Depends on your mental and physical state, how far ahead you are looking on the road, how quickly you identify the hazard (SCAN and IDENTIFY)

    Decision Making time
    The time it takes to PREDICT and DECIDE what to do
    Depends on your experience, physical and mental state, as well as how much you are paying attention
    If factors are at their best, this will take 3/4 of a second to occur

    Reaction Time
    The time it takes to EXECUTE your decision – releasing the accelerator and applying the brakes
    If factors are at their best, this will also take 3/4 of a second
    By this time 1.5 seconds have elapsed before the brake pedal has even been touched (this total varies greatly depending on the driver)

    Braking Time
    The time it takes for your vehicle to come to a complete stop once the brakes are applied
    Depends on your experience and skill in braking, the road conditions, and the kinetic energy of your vehicle

    Screen Shot 2014-02-18 at 11.02.47 AM

  • Distances

    Total Stopping Distance
    The distance your vehicle will travel from the moment you see a hazard to the moment you have brought the vehicle to a complete stop
    – As speed increases, stopping distances do as well.
    – If speed doubles, the braking distance more than doubles due to the increase in Kinetic Energy

    This chart is for ideal conditions; the braking is almost DOUBLE on wet roads, and nearly up to SIXTEEN TIMES longer on icy roads.

    Safe Following Distance
    It is important to stay out of the “Danger Zone (space in which you are too close to stop safely) Lengthen the following distance taking into consideration
    – your speed
    – road conditions
    – the weather conditions
    – the density of traffic
    – the level of your previous experience with the existing conditions