Total Stopping Distance

The Total Stopping Distance calculator computes the distance to stop a vehicle based on the initial velocity (v_i), reaction time (t) and the a braking coefficient (μ).

Compute Total Stopping Distance

1. Choose units (default: kilometers per hour and seconds)
2. Enter the initial velocity (v)
3. Enter the Reaction Time (t)
4. 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
• v_i  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).