Various articles suggest that the maximum release force for buckle according to Federal Motor Vehicle Safety Standards (FMVSS) 109 of 133 N is beyond the capability of a large percentage of our population [1, 2]. Inversion studies with a large male in a three-point production belt showed he could not open a side release buckle [3]. Numerous articles and patents reference the potential for entrapment of inverted occupants unable to release the seat belt buckle [4–11]. Various articles and patents discuss the problems associated with entrapment of individuals in fires, water or emergency situations or where the occupant is deprived of oxygen due to positional asphyxia [12]. While the use of seat belts has increased markedly over the years [13], investigations indicate that rollover accidents showed fatally injured occupants in their seats which were entrapped in their vehicle. The forces to release the buckles under full load of the inverted occupants were beyond the physical capacities of the occupants involved. Canadian motor vehicle safety standard 209 (CMVSS 209) requires that a buckle must release with a force of 133 N to the button with a restraining loop force of 666 N. About 80 % of driver’s could not release a buckle that requires 133 N of force on the button [1]. Females could exert about 80 N with their fingers when opening child restraint buckles [14]. Females were generally found to have about half the physical capacity to open buckles compared to males. The maximum buckle release force of 133 N is not found in literature. Dreyfuss in his book indicates various forces for females and males [15]. European standards require that latch plate be ejected, therefore side release buckles are not allowed.

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