Impact Severity Analysis

BME’s engineering professionals have analyzed thousands of motor vehicle collisions involving automobiles, commercial vehicles, motorcycles and recreational vehicles. Determining the impact severity of a collision provides the collision reconstruction engineer valuable information when calculating pre impact speeds and determining risk of injury to vehicle occupants.

Impact severity is most commonly quantified in terms of the Delta V (the change in velocity of the vehicle during the collision given in m/s ) and PDOF (principal direction of force). Impact severity may also be quantified in terms of acceleration, expressed in units of “G”.  One G is equal to the acceleration of the earths gravity (9.81 m/s2 ). In context, any object in freefall accelerates downwards at 1G, hard braking may cause 0.5G and severe collision may cause in excess of 20G.

Determining a range of collision severity values provides the collision reconstruction engineer with an indicator for calculating probability of injury. Probability of injury and severity of injury both increase with Delta V and G values.


Jonathan P. Gough P.Eng.
David M. Little P.Eng.
D. Harvey West P.Eng.