The Total Stopping Distance calculator computes the distance to stop a vehicle based on the initial velocity (vi), reaction time (t) and the a braking coefficient (μ).
Compute Total Stopping Distance
- Choose units (default: kilometers per hour and seconds)
- Enter the initial velocity (v)
- Enter the Reaction Time (t)
- Enter the Braking Coefficient (μ)
Total Stopping Distance (TSD): The calculator returns the distance (TSD) in meters. However this can be automatically converted to other distance units via the pull-down menu.
The Math / Science
The Total Stopping Distance is the sum of the perception-reaction distance and the breaking distance. A common baseline value of reaction time is 1.5 seconds (`t=1.5 s`), and `mu=0.7` is used in stopping distance charts. These values incorporate the ability of the vast majority of drivers under normal road conditions. However, a keen and alert driver may have perception-reaction times well below 1 second, and a modern car with computerized anti-skid brakes may have a friction coefficient of 0.9 - or even far exceed 1.0 with sticky tires.
The breaking distance is one of two components of total stopping distance. The following formula is used to calculate the total stopping distance:
TSD =v•t+v²/(2•μ•g)
where:
- TSD is the total stopping distance
- vi is the initial velocity
- t is the reaction time
- μ is the friction factor
- g is the acceleration due to gravity on earth
Braking Coefficient
The Braking Coefficient is a coefficient of kinetic friction. For accident reconstruction on dry surfaces, a value of 0.7 is often used. This is the default value in this calculator.
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References
The formula and definition are from Wikipedia (https://en.wikipedia.org/wiki/Braking_distance).