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Accident Reconstruction Calculators

Below are some basic accident reconstruction tools. They should be used to estimate ranges of answers for common reconstruction calculations. Most problems involves more complicated factors so make sure to consult an Automotive Engineer. 

Skid Distance from Speed

This equation is used to estimate how far it takes a vehicle to stop from a given speed with a maximum (100%) braking force. The stopping distance can be estimated using the speed  before braking and the Coefficient of Friction* of the road surface. This equation is a rearrangement of the Speed From Skids equation.


Braking Distance = (Pre-Braking Speed)^2 / (30 x Coefficient of Friction)

Or:            D = (S)^2 / (30xF) 


D = Stopping Distance (feet)

S = Pre-Braking Speed (mph)

30 = Conversion factor (converts feet per second to miles per hour)

F = Coefficient of Friction


*The Coefficient of Friction quantifies the amount of adhesion between the road surface and the vehicle’s tires. Slippery roads (wet, icy, etc.) have lower Coefficients of Friction than dry road surfaces. A range of Coefficients of Friction should be used to achieve a realistic range of answers.

Example Calculation:

A vehicle is traveling at 65mph on wet Asphalt. How far would it take the vehicle to come to a complete stop?

Low: D = (S)2 / (30xF) = D = (65)2 / (30x0.75) = 188 feet

High: D = (S)2 / (30xF) = D = (65)2 / (30x0.40) = 352 feet

Answer: 188 – 352 feet

COEFFICIENTS OF FRICTION OF VARIOUS ROADWAY SURFACES                            DRY                               WET                      

ASPHALT OR CONCRETE                                                                                        From 0.70 to 0.95                From 0.40 to 0.75

GRAVEL                                                                                                                      From 0.40 to 0.80                From 0.40 to 0.75

SNOW                                                                                                                         From 0.10 to 0.35                From 0.30 to 0.60

ICE                                                                                                                               From 0.07 to 0.20                From 0.05 to 0.10

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