In low speed rear-end collisions, the effects of vehicle braking and variations in vehicle-to-vehicle contact stiffness on global vehicle kinematics are potentially important for injury causation, but these have not yet been evaluated and the relative importance of each is unknown. To address this, we developed a model of vehicle kinematics for target and bullet vehicle braking and no-braking conditions in full-engagement low speed rear-end collisions. The model was assessed by comparison with staged AGU collisions and then applied to assess the relative influence of target and bullet vehicle braking on average acceleration and SPUL profiles of the target vehicle. Results show the model provides, on average, a close match to the average and peak vehicle accelerations when compared to the available full-engagement AGU cases. Further, Monte Carlo predictions accounting for variations in vehicle stiffness and mass ratio showed a close match to the available experimental data for both braked and unbraked cases. Application of the model shows that vehicle braking has a small but identifiable influence on the collision closing speed required to reach reported injury reference levels, while vehicle stiffness and mass ratio have a much more substantial effect.

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