The safety performance of cars is evaluated using standard tests. These standard tests are normally performed with full overlap or 40% overlap from the corner in different speed ranges. Analysis of accident data indicated that the injury severity of car occupants that were involved in accidents that are different compared to the standard tests (e.g., central pole impact) is considerably higher than for those that are similar to the standard tests. One of the discussed possible reasons for this observation is that the restraint system triggering might not be appropriate for these situations.

The combination of NASS CDS data with the NASS EDR data allows to analyse the accident circumstances, the restraint system triggering times and the injury situation in frontal impact accidents. The result of this analysis is a grouping of accident situations with corresponding injury severities and restraint system triggering times. These groups are rechecked using the GIDAS data to confirm the influence of the accident circumstances on the injury severity, as restraint system triggering time is not available in the GIDAS data sample.

The restraint system trigger time depends on several factors (e.g., delta-v, impact configuration (e.g., involving both long members, only one long member or no long member), impact angle etc.). While most of the differences appear to be sensible for optimal protection (e.g., at higher delta-v the airbag is needed earlier) the differences for the different impact configuration appears to be critical with respect to injury severity levels of the frontal occupants.

The shown correlation between crash configuration, restraint system triggering time and injury severity does not necessarily mean that there is a causative relation between triggering delay and increased injury severity. However, it is likely that there is a causative relation.