The Timing of Pre-Crash Data Recorded in General Motors Sensing and Diagnostic Modules

The sampling rate and synchronization of the pre-impact data stored by General Motors (GM) sensing and diagnostic modules (SDMs) have not been experimentally determined. The goals of this study were to measure the time shift between the SDM-reported data times and algorithm enable, sampling rate variation and the synchronization of the sensor data. In this study, two experiments were performed. First, the SDM of a 2002 Pontiac Sunfire was artificially triggered while the throttle position, engine speed, vehicle speed and brake signals were also being monitored at their source sensors. Second, the throttle and vehicle speed sensors were replaced with artificially generated inputs so the timing of the SDM recorded values could be compared to that of the known inputs. Sampling rate and data synchronization were determined by fitting the SDM recorded values to the measured sensor outputs. Both the field and laboratory tests showed that there was temporal uncertainty in all of the recorded pre-impact data. The SDM-reported pre-crash data points were sampled up to 1.5 s closer to algorithm enable than indicated in the SDM download. The study provides a better understanding of the effects of the pre-impact data timing for accident investigators.