Reconstructing Vehicle and Occupant Motion from EDR Data in High Yaw Velocity Crashes

Among the several data recorded by a typical motor vehicle’s event data recorder (EDR) prior to, during and after a crash event, are sampled time histories of longitudinal and lateral components of delta-v. The delta-v components are not measured directly but are calculated by numerically integrating the outputs of two perpendicular accelerometers contained within the EDR box. As currently designed and implemented a typical EDR does not measure yaw velocity or track vehicle heading during the impulse phase of a crash. Without this yaw information to orient the accelerometers relative to the fixed ground, the delta-v values calculated by the EDR through direct integration of its measured acceleration components should not be interpreted as representing absolute changes in vehicle velocity, especially in cases where the yaw velocity is high. EDR-calculated delta-v components must be adjusted to account for the yaw motion that occurred during acquisition of the data. With reasonable time-history estimates of yaw velocity and measurements of the EDR and vehicle CG locations, the delta-v components calculated and recorded by the event data recorder can be differentiated and transformed to determine the vehicle’s absolute acceleration and velocity change and its corresponding translational and rotational displacements during and immediately following the collision event that triggered the EDR to make a record.