1984-10-01

Influence of Vehicle Front Geometry on Impacted Pedestrian Kinematics 841663

A primary cause of severe injury experienced by a pedestrian who is impacted by the front of a vehicle consists in the head impact on the hood during the loading phase of the accident. Impact speed and vehicle front geometry are the most important factors which govern the severity of this impact. The aim of the present study is to analyse the motion patterns occuring during impact, particularly those of the head, and to identify a favourable front geometry in view of a reduced injury hazard.
The investigations are based on impact tests performed on a sled with a vehicle front having a variable front geometry and at different impact speeds. The surrogate was a modified 572 ATD (HUMANOID) equipped with 18 accelerometers and whose head trajectory during impact was determined by high-speed cine-photogrammetry. Moreover, mathematical simulation was applied to the problem utilizing an extended version of the CALSPAN CVS computer program.
At a given bumper lead angle the impact speed of the head on the hood is found to decrease with increasing height of the upper leading edge of the front within certain limits, while the pelvis load increases. Likewise, at a given upper leading edge of the front the surrogate loadings mentioned above show a similar behaviour with increasing bumper lead angle. In both cases the pedestrian kinematics undergo significant, characteristic changes as a result of the variations. In spite of the fact that the head and the pelvis loading exhibit an opposite dependence of the two parameters, it is shown that for an adult pedestrian of average height the front geometry can be adjusted such that an overall injury reduction can be expected in a certain range of impact speeds. This range, however, is important in innercity traffic.

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