The aim of this work was to determine the extent to which the secondary safety performance of passenger vehicles may have been optimised with regard to the Regulatory and EuroNCAP impact tests. Such optimisation could, potentially, lead to reduced protection at other impact severities and for other occupant sizes.
Two vehicles were selected based on detailed analysis of EuroNCAP data: one fitted with a dual stage airbag and one fitted with a single stage airbag. Both of the cars had seat-belt pre-tensioners.
Full-scale vehicle and sled tests were conducted to evaluate their safety performance over a range of impact severities using different sized dummies. The full-scale frontal tests were conducted into a 40% overlap offset deformable barrier at 56km/h and 64km/h. The sled tests were conducted at a velocity of 40km/h, determined from an analysis of Co-operative Crash Injury Study (CCIS) accident data as a threshold for the onset of life threatening injuries. Sled tests were also carried out at 56km/h to allow comparison with full scale tests.
This research has identified that, for the vehicles tested, the restraint system ensures a high level of protection for 50th percentile occupants during the 64km/h EuroNCAP test condition, but this same protection is not necessarily ensured at lower crash severities, or for smaller and larger occupant sizes. The Regulation test prescribes limit values corresponding to 50% risk of severe thoracic injury and the EuroNCAP test encourages restraint system design corresponding to a 5% risk of severe thoracic injury. If it is considered that ‘best practice’ is achieved during the 64km/h EuroNCAP test with 50th percentile occupants, then manufacturers should be encouraged to achieve this same high level of protection, or greater, during range of impact severities and for all occupant sizes. This research proposes the requirement of additional testing to achieve this goal.

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