The air bag suppliers and vehicle manufacturers are working on a wide range of advanced technologies to upgrade air bag system performance, including but not limited to addressing adverse effects of air bags to out-of-position occupants. To illustrate the kinds of technological opportunities that are available, NHTSA is including a discussion on this subject presented by JPL in the Executive Summary of its Advanced Air Bag Technology Assessment. For additional information, interested persons are referred to the full JPL report, NHTSA's Preliminary Economic Assessment for this proposal and the references it cites, and the docket for this and other notices relating to Standard No. 208.
The JPL Executive Summary includes the following discussion of technological opportunities (section numbers are omitted):
Model year 2001. The technologies that are being developed and that may be available for model year 2001 provide both improved information and improved response.(17)
Information
- Crash sensor/control systems with improved algorithms will better discriminate when air bag deployment is necessary for occupant crash protection, will provide better threshold control, and will determine the appropriate inflation level for two-stage inflators.
- Belt use status sensors can detect when an occupant is belted so that the air bag deployment threshold can be raised when belts are in use. (These are currently in use in some cars.)
- Seat position sensors provide an approximate surrogate measure of occupant size and proximity to the air bag module. They can be used in combination with belt status sensors to determine the appropriate inflator output.
- Seat belt spool-out sensors could provide additional information about an occupant's size and proximity to the air bag module. These sensors were not mentioned as being part of any current industry use strategy and therefore may not be available by model year 2001.
- Static proximity (occupant position) sensors could identify occupants in the keep-out zone, but will be available only if an aggressive development program is undertaken. They would not reduce injuries to all out-of-position occupants, and they could be "fooled" some of the time.
- Automatic suppression can prevent inflation when sensors determine that an occupant is in a keep-out zone where injuries could occur.
- Two-stage inflators can permit relatively soft inflation for crashes of lower threshold velocity, and full inflation when necessary for crashes of high threshold velocity.
- Compartmented air bags, radial deployments, and bags with lighter-weight fabrics may reduce the size of the keep-out zone.
- Advanced belts can improve restraint system safety and protectiveness. They may include pretensioners that can provide better coupling of the occupant to the seat for improved ride-down during the crash. Also, they can, to some degree, limit occupant proximity to the air bag module. Load limiters can also improve belt performance by reducing maximum belt loads on the occupant. (Pretensioners and load limiters are currently in some vehicles.)
Information
- Crash sensor/control system algorithms will continue to be improved.
- Belt use sensors will be widely used already.
- Integrated occupant and proximity sensors could be available that would identify occupants in the keep-out zone or those who would enter it.
- Precrash sensors may be available, but their application requires further investigation.
- Automatic suppression to prevent inflation will be available for use with proximity sensors.
- Multistage inflators to provide more tailored responses for a variety of occupants and crash severities could be available, if needed.
- Bag designs will continue to be improved, permitting a reduction of the keep-out zone.
- Pretensioners and load limiters will be placed in increasing numbers of vehicles. Air belts will be available to improve safety belt effectiveness.
NHTSA notes that the JPL report presents tables listing specific technologies for advanced safety restraint systems and providing a summary of advanced technology characteristics. The technology items discussed in the JPL report include:
Sensors:
--Pre-Crash Sensing
--Crash Severity Sensors
--Sensing Diagnostic Modules/Crash Algorithms
--Belt Use Sensors
--Belt Spool-Out Sensors
--Seat Position Sensors
--Occupant Classification Sensors
--Occupant Proximity Motion Sensors
--Computational Systems/Algorithms
Inflators
--Non-Azide Propellants
--Hybrid Inflators
--He>ated Gas Inflators
--Multistage Inflators
--Inflators With Tailorable Mass Flow Rate
Air Bags
--New Fabrics and Coatings
--New Woven Fabrics and Bag Construction
--New Bag Shapes and Compartmented Bags
--New Air Bag Venting Systems
Seat Belt Systems
--Pretensioners
--Load Limiting Devices
--Inflatable Seat Belts
The JPL report also presents an assessment of the merits of advanced technologies.
The JPL report cautioned that expected improvements in the safety and protectiveness of air bags must be tempered by the understanding that there are key technology developments that need to be accomplished, namely:
- Air bag deployment time variability must be reduced by improvements in the vehicle crush/crash sensor system.
- Inflator variability must be reduced so that dual-stage inflators can be applied effectively.
- System and component reliability must receive diligent attention to achieve the high levels required under field conditions.
- Occupant sensors must be developed that can distinguish with high accuracy small, medium, and large adults; children; and infant seats.
- Position sensors to measure occupant proximity to the air bag module with the required response time and accuracy must be demonstrated.
The JPL report also notes that its projections of technology availability are based on limited contacts with a limited number of vehicle manufacturers and suppliers, and that the state of the art of advanced air bag technologies is in a high state of flux. The report notes that the projected technologies, as well as other technologies, may advance more or less rapidly than indicated.
NHTSA has had more extensive contacts than JPL with suppliers and vehicle manufacturers, and more recent ones. Based on confidential information shared with the agency during those contacts, NHTSA believes that the JPL report is conservative in its assessment of the stages that some suppliers have reached in developing new technologies and the model year in which some of the very highly advanced air bag designs will first be introduced.
NHTSA recognizes, however, that different suppliers and vehicle manufacturers are at different stages in their development of advanced air bags, and also face different constraints and challenges, e.g., different states-of-the-art of their current air bag systems, engineering resources, number of vehicles for which air bags need to be redesigned, etc.
The agency believes the proposed date for the beginning of the phase-in, the phase-in itself, and also the proposal of a number of manufacturer options to reflect different available design choices, would accommodate these differing situations.
