Journal Article Title: Forensic Engineering Analysis and Testing for Speed Reduction in Transient Braking
Article Author(s): Castaneda, Rene A., P.E.
Volume: 20
Volume #: 2
Month: December
Year: 2003

Download this paper


The 'speed from skids' equation is derived from the Work-Energy theorem and is often employed in accident reconstruction to determine a vehicle’s speed at the onset of visible locked-wheel braking application. The conventional use of this equation in the field of accident reconstruction, however, does not yield a vehicle’s true speed at the onset of braking. In maximum application of the brake pedal, a vehicle initially undergoes a transient brake phase prior to arriving at the quasi-steady-state locked-wheel brake phase. There is a reduction of speed that occurs during the transient phase of braking that is generally not accounted for in the reconstruction of vehicular collisions. Accounting for this reduction in speed, a forensic engineer can estimate a vehicle’s speed at the onset of braking and further employ the relative elapsed time in collision avoidance calculations. This study will explore a method to estimate the speed reduction occurring during the transient braking based on field testing.