AN OVERVIEW OF NHTSA’S CRASH RECONSTRUCTION SOFTWARE WinSMASH

The National Highway Traffic Safety Administration (NHTSA) uses WinSMASH computer software to estimate the change in velocity, delta-V, of the vehicles involved in crashes. The software uses detailed measurements from the crash scene, vehicle damage and vehicle stiffness characteristics to compute energy absorbed by the vehicle and estimate the delta-V and Barrier Equivalent Speed (BES). The WinSMASH is a Microsoft Windows based, enhanced and updated version of the accident reconstruction software CRASH3 previously used by NHTSA. The purpose of this paper is to describe the new enhancements in the program. The damage algorithm used in CRASH3 has been reformulated in WinSMASH. The new damage algorithm in WinSMASH is based on an assumed linear relationship between crash energy and crush and uses intercept d0 and slope d1 to describe vehicle stiffness. The software uses generic vehicle size and stiffness categories based on the vehicle’s wheelbase. However, the program also allows the users to enter the vehicle specific stiffness coefficients. The stiffness coefficients for a large number of vehicles have been calculated from crash test results and integrated into WinSMASH. An automated procedure to select the vehicle specific stiffness coefficients is currently under development. A statistical model is also being developed for estimating the stiffness coefficients of a vehicle that is not crash tested. The paper provides an overview of these procedures. The WinSMASH estimated delta-V of the vehicles is compared with the corresponding delta-V obtained from the Event Data Recorder (EDR) installed in the crashed vehicles to assess the accuracy of the software. The staged crash tests used to validate the software are also discussed in the paper.