Commercial Vehicle Event Data Recorders and the Effect of ABS Brakes During Maximum Brake Application

Many commercial vehicles have an event data recorder (EDR) that can record pre-event and post-event information. In this study, information from brake applications were studied to determine how the EDR data can be used to evaluate brake initiation time and vehicle deceleration rate. The study shows the effect of the ABS brake system on the electronic control module (ECM)-reported speed. The ECM-reported speed was compared to the speed measured by a calibrated optical 5^th wheel and a GPS speed measuring system. The results show that the trend of the ECM-reported speed can be used as a predictor of the time when brake application first began. The results also show that under certain conditions the ECM-reported speed can be used to evaluate the deceleration rate of the vehicle. The results also show the ECM-reported speed is underreported during hard brake application due to the ABS brake function.