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`v = sqrt( 30*L*fc)`

Enter a value for all fields

The **Speed from Length of Skid Marks** calculator estimates the speed based on the length of skid marks and the friction coefficient.

**INSTRUCTIONS:** Choose units and enter the following:

0.05 | Very Slippery Conditions |

0.7 | Normal Dry Conditions |

0.9 | Ideal Breaking Conditions |

- (
**L**) Length of Skid Marks - (
**fc**) Friction Coefficient

**Speed from Length of Skid Marks (v):** The calculator returns the speed in miles per hour. However this can be automatically converted to other velocity units (e.g. kilometers per hour) via the pull-down menu.

The formula for the velocity based on the length of skid marks is:

`v = sqrt( 30*L*fc)`

where:

- v = initial velocity
- L = Length of Skid Marks
- fc = friction coefficient (0.05 for very slippery to 0.9 for ultimate breaking)

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. A modern car with computerized anti-skid brakes may have a friction coefficient up to 0.9.

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- Braking Distance
- Total Stopping Distance
- Speed from the Braking Distance
- Speed from Length of Skid Marks

- The Traffic Accident Investigation Manual, by J. Stannard Baker and Lynn B. Fricke