Another part of the agency's proposal that is intended to enhance the benefits of air bags is to require vehicles to meet performance requirements for 5th percentile adult female dummies in the same tests long specified for 50th percentile adult male dummies.
Accordingly, the agency is proposing to require vehicles to meet specified injury criteria, including criteria for the head, neck, chest, and femurs, measured on 5th percentile adult female test dummies during a rigid barrier crash test at any speed up to 48 km/h (30 mph) and at the same range of angles applicable to the tests using 50th percentile male dummies. Under the proposal, vehicles must meet the criteria both with the dummies belted and unbelted.
Certain of the proposed injury criteria differ from those specified or proposed for 50th percentile adult male dummies to reflect the different injury risks faced by 5th percentile adult females. Dummy seating positions are also adjusted to reflect 5th percentile adult females. The agency is proposing that tests be conducted with the dummies seated in a full forward position. While many 5th percentile adult females can sit further back, the proposed test will ensure that protection is provided in a more extreme position, but one where air bags can still provide protection.
NHTSA is proposing to specify the use of the Hybrid III 5th percentile adult female dummy. The Society of Automotive Engineers has guided the development of this dummy, and that work is nearly complete. Therefore, the motor vehicle industry is familiar with this dummy. NHTSA has not, however, yet proposed to add this dummy to Part 572, the agency's regulation containing specifications for the various dummies it specifies in the Federal motor vehicle safety standards. The agency expects to propose adding the Hybrid III 5th percentile adult female dummy to Part 572 later this year.
NHTSA is also proposing one additional barrier test requirement using 5th percentile adult female dummies, an up to 40 km/h (25 mph) offset deformable barrier test requirement, using restrained dummies.
Research conducted by Transport Canada has shown that one of the causes of adverse effects of air bags is late deployment of some air bags in crashes with a "soft crash pulse." In order to reproduce the softer, longer duration crash pulse, it selected the 40 percent offset barrier. It conducted crash tests into the barrier at 8 km/h (5 mph) increments up to 40 km/h (25 mph). These tests were conducted with a 5th percentile adult female belted dummy in a full-forward position, to simulate short stature drivers and the high belt use pattern in Canada. It found that at 40 km/h (25 mph), all the air bag systems of the vehicles tested would deploy. It also found that even for a belted driver, the deployment of the air bag frequently was so late that the test dummy would be right on the steering wheel, a "worst case" condition. The test procedure was shown to be a good test for the head, neck and chest loading on the dummy by the air bag.
NHTSA notes that the timing of air bag deployment is determined by a vehicle's crash sensing system, including both the crash sensing hardware and associated computer algorithm, i.e., the software. The decision to deploy an air bag is necessarily predictive, that is, the decision that a crash will be severe enough to warrant air bag deployment must be made very early in the crash if the air bag is to deploy in time to provide protection. The work done by Transport Canada, as well as other research, has indicated that the crash sensing systems of some vehicles need to be improved to better evaluate some crash pulses.
The agency is proposing a 40 km/h (25 mph) offset deformable barrier crash test requirement to help ensure that vehicle manufacturers upgrade their crash sensing and software systems, as necessary, to better address soft crash pulses. The proposed test is essentially the one that Transport Canada has been conducting for purposes of research. Restrained 5th percentile adult female dummies would be positioned in the same full forward position being proposed for the rigid barrier test discussed above, and the same injury criteria limits would apply. Since this is a relatively low energy test, it should be very easy to meet the injury criteria limits so long as the air bag deploys early in the crash event before the dummy moves very far forward.
Based on the testing conducted by Transport Canada, the problem of late deployments appears to be a problem with only some vehicles, at least in the environment measured in this particular crash test. The agency expects that the problem can be solved using a number of readily available approaches. These include improving computer algorithms, and adding crash sensors, e.g., using extra sensors mounted in the crush zone of the vehicle to provide additional, and earlier, information to use in the decision making algorithm. A longer term means of ensuring that air bags deploy early in a crash would be to use anticipatory crash sensors.
The agency is also proposing specifications for the deformable barrier to be used in this test. The specifications for this barrier would be included in Part 587.
