In the 1999 Supplemental Notice for Proposed Rulemaking (SNPRM) for Advanced Airbags, the National Highway Traffic Safety Administration (NHTSA) sought comments on the maximum speed at which the high-speed, unbelted occupant test suite will be conducted, i.e., 48 kph vs. 40 kph. To help address this question, an analysis of constraints was performed via extensive mathematical modeling of a theoretical restraint system. First, math models (correlated with several existing physical tests) were used to predict the occupant responses associated with 336 different theoretical dual-stage driver airbag designs subjected to six specific Regulated and non-Regulated tests. Second, the pertinent, predicted occupant responses for all 336 designs were compared with a set of generic acceptance criteria for the six distinct performance constraints (where two of the six represented the aforementioned “high-speed” unbelted occupant test suite and where “high-speed” was set equal to either 48 or 40 kph). Finally, statistics were generated to help evaluate the stringency of the various performance constraints.
Results from the assessment for a modeled, prototype, mid-sized passenger car included the following: (1) None of the 336 theoretical dual-stage driver airbag designs satisfied the generic acceptance criteria set when the unbelted rigid fixed barrier testing constraints were run at 48 kph, (2) 21 of the 336 satisfied the generic acceptance criteria set when the unbelted rigid fixed barrier testing constraints were run at 40 kph, and (3) When considering the discarded designs, nearly all of them were predicted to not comply due to (at least one of) the unbelted occupant performance constraints of the generic acceptance criteria set.