Boundary conditions for setting thorax impactor subsystem tests to assess vehicle safety performance on protection of vulnerable road users

Chinese automobile safety regulations are considering the introduction of thorax impactor subsystem tests to evaluate vehicle safety performance concerning thorax protection for Vulnerable Road Users (VRUs). However, there is currently an insufficient amount of data regarding VRU thorax-vehicle contact boundary conditions, which is essential for establishing the thorax impactor test procedure. Consequently, the objective of this study is to examine the characteristics of VRU thorax-vehicle contact boundary conditions, utilizing multi-body crash simulations that are informed by the distribution of accident scenarios. The simulation data suggest that the boundary conditions for thorax-vehicle contact in VRUs are predominantly influenced by the relative height of the VRU’s pelvis in relation to the vehicle’s bonnet leading edge, which in turn affects upper body kinematics. This results in variations across different vehicle and VRU types involved in collisions. The analysis of these contact boundary conditions indicates that thorax impactor subsystem test procedures should differentiate between vehicle types. The results suggest that: thorax impactor subsystem tests should concentrate on the Wrap Around Distance (WAD) range of 900 to 1800 mm; for testing at the bonnet-windscreen area, the thorax impactor could be launched at speeds of 16.5 km/h (with a vector angle of 24° and an initial inclination angle of 17°) for sedans, and 23.5 km/h (with a vector angle of 25° and an initial inclination angle of 22°) for SUVs/MPVs. Additionally, a horizontally directional velocity of 35.5 km/h (with an initial inclination angle of 30°) could be specified for thorax impactor tests at the bonnet leading edge area of SUVs/MPVs. The above data provides foundational data for future thorax impactor subsystem tests in China.