Airbag, Automobile
Seat belts have been proven to be effective in saving lives and preventing or lessening injuries in automobile accidents. The key to their success, however, is that occupants must use these safety devices. Because seat belts require active use by the wearer, inventors developed passive restraints to ensure driver and passenger safety. The first passive restraints were modifications of seat belts themselves; the belts were coordinated with operations of opening the car doors and starting the automobile, which caused belts built into tracks in the doors to wrap around the driver or passenger when the seat was occupied. Concurrently, the airbag was devised as a secondary form of passive restraint during impact.
In 1961, Arnold Kent of England considered the use of inflatable cushions. He suggested they could be stowed in front of the occupants and would inflate automatically from a container of compressed gas in the event of a collision. In the United States, automotive engineers developed Kent's idea further. Air cushions made of nylon-reinforced plastic were stored in the hub of the steering wheel on the driver's side and in the dashboard on the passenger's side of the front seat. In serious front-end collisions (the equivalent of hitting a brick wall at a speed greater than 12 miles per hour), crash sensors activate the airbags. Within 1/25th of a second after impact, the bag inflates to cushion the driver or passenger from hurtling forward into the steering wheel, dashboard, or windshield. The bag then deflates rapidly so the occupant can get out of the vehicle. A solid chemical, sodium azide, triggers the nitrogen gas used to inflate the bag.
Unfortunately, airbags themselves were proven to cause death and injury. The National Highway Safety Administration (NHSA) found that more than 50 drivers and passengers lost their lives due to impact from airbags in the period from 1994 through 1996, and a number of those injured or killed were children. Airbags had been designed based on car occupants of average size, so the force and direction of impact of the bag itself could hurt children or small adults. Lobbyists and others proposed that cutoff or deactivation switches be installed in automobiles so the driver would have the option of preventing the passenger-side airbag from working. Fear that riders would now stop using both seat belts and airbags prompted the NHSA to ask car manufacturers to develop "smart" airbags that would sense more accurately the sizes of the car's occupants and adjust the amount of inflation accordingly.
"Smart" airbags are being developed. A switch under the seat measures the occupant's position in the seat, and a piezoelectric crystal (like those used in electronic bathroom scales) weighs the occupant. These data tell a microprocessor whether or not to inflate the bag, by how much, and how quickly. A still more sophisticated measuring system in development uses a camera (standard video cameras, infra-red devices, and ultrasonic transceivers are being considered) to detect the rider's size and position in the seat. Ultimately, a radar sensor in the front of the car may anticipate impact and deploy the bag before the accident occurs.
The "smart" airbag must also inflate safely. Compressed helium (instead of nitrogen) is being studied, and dual-stage inflators may be used in which the first stage only inflates for small-sized occupants and a second stage is triggered if the rider is large. Widespread use of "smart" airbags is expected by the year 2000; in 1996, Mercedes introduced a system that disables the airbag when a child safety seat is locked into position, and side impact bags also became available in some car models in the mid-1990s.
Honda is exploring a new system that will eliminate the airbag controversy altogether; it has developed an "Air Belt", which is a safety belt with an inflatable shoulder portion that inflates on impact to prevent head movement and to cushion the body. Air Belts can be used to protect back-seat as well as front-seat occupants, and they inflate away from the wearer instead of creating a point of impact by inflating toward the occupant. The parts of the Air Belt are a control unit that signals an inflator to inflate the seatbelt shoulder. The seatbelt tenses during the process so the belt itself is not slack, and the belt deflates rapidly as it absorbs the impact. The Air Belt is also less expensive to produce and install than airbags embedded in dashboards and steering columns. Honda expects to begin marketing the Air Belt in 1998-1999. Regardless of future developments in airbags, the automobile passenger's first line of defense is the seat belt, and other devices should be used in conjunction with seat belts.
This is the complete article, containing 773 words
(approx. 3 pages at 300 words per page).
