Numerical Methods for Evaluating ECM Data in Accident Reconstruction and Vehicle Dynamics

Information stored in the electronic control modules (ECM) of modern class 8 tractors is a valuable tool to accident reconstruction, but must be properly interpreted. The stored ECM speed data is driveshaft speed. To determine the road speed, the investigator must determine if braking occurred. The level of braking can be estimated from the data and computation of the road speed from the driveshaft speed can be performed by estimating the tire slip. Failure to determine the road speed can result in substantial error in velocity and travel distance estimates. Using realistic models it is shown that proper numerical integration techniques will produce negligible error in highway speed braking distances.