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This paper summarizes the findings of a study undertaken by Transport Canada to examine the primary mechanisms of injury to front seat occupants restrained by conventional three-point seat belt assemblies. The study involved the early retrospective investigation of collisions, in defined geographic areas across Canada, in which at least one occupant involved was fully restrained. The pattern of injury to 314 full restrained occupants who sustained at least one injury at the AIS 2 or greater severity level is examined in the present paper. Overall, the head/face and chest were found to be the most frequently injured body regions. In the case of drivers, facial injuries were invariably associated with the steering wheel, whereas head injury was more likely to be associated with interior side and roof structures. Injuries to the shoulder/chest and pelvic/abdomen regions among drivers were usually associated with direct contact with either the steering wheel or the interior side surfaces.

Drawing on field data gathered during the course of Transport Canada's Fully Restrained Occupant Study (FROS), the current limits of protection afforded vehicle occupants restrained by conventional three-point seat-belt assemblies in side impacts are examined. The sample under consideration comprises 98 restrained passenger vehicle occupants involved either in a near side or a far side impact, each of whom sustained at least one injury at the AIS 2 or greater severity level (1976 AIS Dictionary). A detailed description of the pattern of injury to this subset of occupants and the damage sustained by the vehicle is presented. The principal mechanisms of injury for various body region groupings are discussed, with special attention being given to the incidence of side compartment intrusion. Other factors influencing injury potential such as occupant age and vehicle size are also discussed.

An evaluation of the four injury risk curves proposed in the NHTSA NCAP for estimating the risk of AIS≻=3 injuries to the head, neck, chest and AIS≻=2 injury to the Knee-Thigh-Hip (KTH) complex has been conducted. The predicted injury risk to the four body regions based on driver dummy responses in over 300 frontal NCAP tests were compared against those to drivers involved in real-world crashes of similar severity as represented in the NASS. The results of the study show that the predicted injury risks to the head and chest were slightly below those in NASS, and the predicted risk for the knee-thigh-hip complex was substantially below that observed in the NASS. The predicted risk for the neck by the Nij curve was greater than the observed risk in NASS by an order of magnitude due to the Nij risk curve predicting a non-zero risk when Nij = 0. An alternative and published Nte risk curve produced a risk estimate consistent with the NASS estimate of neck injury.

Static out-of-position tests were performed to identify the potential for injury as a function of position, airbag type and vehicle seat characteristics. Seat and door mounted airbags, head curtains and head tubes were evaluated. Out-of-position testing was carried out with the Hybrid III 3 year old, 6 year old and the TNO Q3 3 year old child dummies. In-position tests and a dynamic test were conducted to monitor child seat and airbag interactions and to confirm that properly restrained children would not be exposed to undue risk from a deploying side airbag. Results of the out-of-position testing suggest that current side airbag designs may cause serious and/or fatal neck and chest injuries. In-position static testing with child seats suggested a potential for intrusion into the child occupant space leading to structural damage of the car seat.

With the current trend of including the evaluation of the risk of brain injuries in vehicle crashes due to rotational kinematics of the head, two injury criteria have been introduced since 2013 – BrIC and DAMAGE. BrIC was developed by NHTSA in 2013 and was suggested for inclusion in the US NCAP for frontal and side crashes. DAMAGE has been developed by UVa under the sponsorship of JAMA and JARI and has been accepted tentatively by the EuroNCAP. Although BrIC in US crash testing is known and reported, DAMAGE in tests of the US fleet is relatively unknown. The current paper will report on DAMAGE in NCAP-like tests and potential future frontal crash tests involving substantial rotation about the three axes of occupant heads. Distribution of DAMAGE of three-point belted occupants without airbags will also be discussed. Prediction of brain injury risks from the tests have been compared to the risks in the real world.