Calculate Vehicle Speed from Skid Mark Distance

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Vehicle Speed Calculator over Multiple Surfaces with an Impact

This calculator is used to calculate the speed of a vehicle traveling over one or more surface types and takes into account an impact with another vehicle or object.

This calculator can be used if there aren't multiple roadway surface types or an impact. In this situation just leave the extra input fields empty.

	Surface 1	Surface 2	Surface 3	Impact
Roadway Friction:
Roadway Slope:	%	%	%
Distance of Skid Mark:	ft	ft	ft
Speed Loss Due to Impact:				mph

When inputing roadway slope data above: Use 0% slope for flat roadway. Use negative sign ( - ) for downhill grade. Example: 2.5 for uphill grade and -2.5 for downhill grade.

Calculator uses the combined speed formula:

S_c = √(S₁² + S₂² + S₃² + S_Impact²)

Where:

S₁ = Speed Loss Accross Surface 1 (mph) = √30*D₁*F₁

S₂ = Speed Loss Accross Surface 2 (mph) = √30*D₂*F₂

S₃ = Speed Loss Accross Surface 3 (mph) = √30*D₃*F₃

S_Impact = Speed Loss Due to Impact (mph)

D = Distance of Skid Mark (feet)

F = Adjusted Friction = μ ± G where μ is the coefficient of friction and G is the grade of the roadway.

The friction table below can be used to approximate the roadway friction based upon different roadway surface types and whether or not the surface is wet or dry.

Coefficients of Friction for Roadway Surfaces

This calculator does not account for hydroplaning conditions and tractor / trailers.

Atlanta Engineering Services, Inc. does not assume any liability for any errors in this calculator. This tool shall not be used for any insurance or litigation purposes. Atlanta Engineering Services, Inc. recommends that a licensed professional engineer specializing in traffic accident reconstruction be consulted for these types of situations.

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