Vehicle acceleration and compartment intrusion play major roles in occupant injury causation, in frontal offset collisions. The knowledge of injury causation may enable the injury risk to be directly assessed from accident conditions, once a relationship between accident conditions and vehicle response is known.
To establish such a relationship, a simulation study was carried out, in which vehicle acceleration and local compartment intrusion were calculated for various crash speeds and overlap configurations. The simulation model was validated against crash-tests in terms of the local vehicle deformation, acceleration and local dash and toepan intrusion.
It was found that average acceleration generally decreased with reduced overlap, while intrusion increased for narrower overlap and impact locations more closely to the dash and/or toepan. This general trend indicates the relatively high injury risk for near-side occupants and a low risk for far-side occupants. Far-side, low-overlap (<50%) offset collisions at 45 or even 50 mph resulted in similar average acceleration and local intrusion levels as those seen in full overlap at 35 mph.
However, crush reaching into the stiff firewall may cause vehicle peak accelerations to rise above expected levels in low overlap and high speed, especially in case the engine enhances firewall deformation. Furthermore, far-side intrusions may reach similar levels as near-side intrusions in offset collisions (>33% overlap), due to induced damage and the load distributing effect of the engine.
Vehicle average acceleration and local intrusion levels may reach injurious levels for the far-side occupant in offset collisions. Vehicle crashworthiness improvements with a sole focus on near-side occupants may result in reduced protection of the far-side occupant.