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Cushioning the Blow: History of Automotive Airbags

While the initial concept for many pieces of automotive equipment grew out of the early days of automotive history, the idea of the airbag did not surface until the early fifties. As with many good inventions, it begins with a good story. John W. Hetrick, a retired industrial engineer, was out for a Sunday drive with his wife and 7-year old daughter Joan in 1952. Driving a 1948 Chrysler Windsor as they tooled down the road just outside Newport, Pennsylvania, the three sat together on the bench seat, a happy fifties family. Just after they crested a hill, suddenly and quite unexpectedly a large boulder appeared in the road. Hetrick threw on the brakes and veered into a ditch. As he did so, both his wife and he instinctively threw their arms into the air in front of their daughter — to shield her from hitting the dashboard. After their nerves settled and they found that no one was hurt, Hetrick found himself still marveling at the close call.

When they reached home, Hetrick went right to the drawing board. He had been a naval engineer and as he thought about some way to shield passengers from a car's sudden stop, an event from his earlier days replayed itself in his mind. In 1944, as he set about repairing a torpedo there had been a sudden release of the compressed air that powered the torpedo, resulting in instant inflation of its canvas cover. The torpedo shot to the ceiling and, understandably, made quite an impression on the young engineer. Patented in 1952 (# 2,649,311), Hetrick developed a "safety cushion" for cars, the forerunner of today's airbags. His design included an under-hood tank for compressed air and front passenger inflatable bags situated on the steering wheel, the glove compartment, and the middle of the dashboard. For rear passengers the airbags were on the back of the front seat. When a spring-loaded weight sensed a quick deceleration, it opened a valve in the compressed air tank and the bag inflated. Hetrick didn't have the funds to develop his idea further, though. He wrote to the big car companies to interest them in his invention but got no response.

It's worth noting, however, that both Ford and GM started working on an inflatable restraint system in the late 50's. They determined that for an airbag to be effective a sensor would have to detect a collision accurately and reliably, and the airbags would have to inflate within milliseconds. The Hetrick sensor was not refined enough and his compressed air idea simply not fast enough to meet the bill.

German inventor Walter Linderer got his German patent (# 896312) for a similar idea about the same time. In his inflatable cushion system, however, the compressed air would be released either by an impacted bumper or by the driver himself.

Innovations in the airbag continued into the sixties when Yasusaburo Kobori, President of the Good Idea Center in Tokyo, demonstrated an inflatable restraint system in Detroit (1962). Carl Clark was thinking about airbags, as well. Head of the Life Sciences Division of Martin's (later Lockeed Martin) Engineering Department in the early sixties, he began working with the idea of airbags to protect astronauts if a space craft crashed. Perhaps recalling stories of WWII fighter pilots who inflated their life vests prior to a crash, he developed a system known as the Airstop Restraint System — which he later tested as an automotive restraint system. It utilized reusable airbags mounted in front of the chest, in front of the feet, and under the seat, inflatable seats, and pressurized air canisters to inflate them. A radar system could detect a coming crash and inflate the bags before impact. Though cars did not come equipped with radar systems, of course, in 1966 at an Iowa conference Clark showed a sketch of his safety car system, promoted the advantages of airbags, and warned of their possible dangers to children. He also testified before Congress, included an early reference to side airbags, and helped legislators determine they wanted to learn more about the efficacy of an airbag system. Clark was definitely a true believer, so much so that at his death in 2006 it was reported that he had been at work on bottle-sized airbags to be embedded in under garments for the elderly to prevent hip fractures.

The first to score a major breakthrough with sensors for airbags was Allen Breed, a former RCA engineer. About 1967 he invented a $5 electromechanical sensor that was safe and reliable. He also secured U.S. patent #5,071,161 on airbags that used two layers of fabric and were vented in such a way that after a passenger came into contact with the airbag, some gas was allowed to escape, providing a safer, less rigid cushion. (Note: In 1987, he formed Breed Automotive to market his safety systems.)

After General Motors had come to Talley Defense Systems (known for its work on propellants for fighter ejection seats) asking for an alternative to the use of compressed air, chemist John Pietz delivered. In 1968 he began using a nitrogen-generating, non-toxic solid propellant — sodium azide and a metallic oxide. That system took up less space than earlier systems but because sodium azide is toxic when ingested in large amounts, its use did little to win converts to the idea of airbag safety. Still, it beat other early ideas hands down. Reasonable attempts were made to use nitrogen, Freon, and carbon dioxide — but there was at least one more adventurous experimenter who used gun powder to heat Freon, producing poisonous phosgene gas which had been used as a lethal chemical weapon during WWI.

Ford meanwhile had approached Eaton, Yale, and Towne, Inc. for assistance, and Eaton invested several million dollars in developing car airbags. Scientist Charles Simon produced an "Auto-Ceptor" air-pillow system, which was ready for rollout by 1971. A sensor was mounted on a car's firewall and, in a crash situation, it activated in 40 milliseconds and sent a signal to the detonator that released nitrogen (pressurized at 2500 psi) into urethane-coated woven nylon airbags. In 1969 Ford demonstrated its ongoing work on airbags. When a team of Ford engineers went to Washington to show the Department of Transportation what they'd been working on, they pushed a button — and (can you guess?) nothing happened. Some innovation. When Henry Ford II heard of the debacle, he was infuriated. Saying he didn't want a Rube Goldberg device in his car, he ended the program— at least temporarily.

Even though car makers had been actively investigating airbag systems, they were not altogether satisfied with the results they saw. The cost of adding airbags, customers' disinterest, and potential liabilities facing them if the airbags failed kept them from moving forward. But the U.S. Government was beginning to become more involved in car safety issues. In August 1966, the National Traffic and Motor Vehicle Safety Act was passed giving the federal government power to regulate car safety. While Henry Ford II memorably said the requirement for lap and shoulder seat belts would force his company to close its doors, few were listening. Roughly a year later the National Highway Traffic Safety Administration (NHTSA) announced a requirement that cars have seat belts by January 1, 1968. When, in 1969, the government proposed passive restraints in cars, largely to protect passengers not wearing seatbelts, GM warned that children sitting too close to an activated airbag could be seriously injured— or worse.

Despite repeated efforts to prevent or delay the mandate for airbags— and questions about what would happen to those who wore glasses or dentures or smoked a pipe— car manufacturers knew the introduction of airbags or some other passive restraint couldn't be far away. Events of the seventies made that expectation a reality. Because seat belt usage was still low then (about 15% used them), some thought that airbags could replace seat belts. It didn't take long, however, for investigators to conclude they could not replace belts, only supplement them.

In 1970 the NHTSA ordered passive restraints for the 1974 model year. Car makers could either install automatic seat belts or airbags; car makers opposed either option. Ford, however, did build an experimental fleet of cars equipped with airbags and was the first manufacturer to say it would introduce airbags in its 1971 line of full-size Lincolns and Mercurys. Their chief body engineer Stuart Frey, however, nixed that idea. He argued there were still poor performance issues, tests on child-size dummies showed injuries were likely, and windshields often broke when airbags were activated. While insurance companies favored the use of passive restraints, car manufacturers continued to oppose them and sued to challenge the rule requiring them.

Armed with complaints and not content to sit and wait for the administrative process to work things out, in April, 1971, Henry Ford II (chairman of Ford) and Lee Iacocca (Ford's president) met with President Nixon in the Oval Office. They related to him that the new safety regulations would put the U.S. at a competitive disadvantage in competing with Japanese car makers and would harm the U.S. economy. Ford's leaders claimed they'd spent $240 million in safety research that had resulted in the addition of new safety features— like the collapsible steering column. But they deemed other devices— like the airbag— a complete waste of money. Just three days after that meeting Nixon's Assistant for Domestic Affairs John Ehrlichman called Secretary of Transportation Volpe to tell him Nixon wanted him to put the brakes on a passive restraint requirement. Soon thereafter a revised ruling, one agreed to by car manufacturers, called for a three-year delay from the '74 models to the '77 ones. When Volpe faced significant political opposition to the delay, he asked to move the mandate to '76 models. Nixon checked with the Big Three, and got their OK.

With a looming deadline, car manufacturers went back to the drawing board. In 1973, GM offered airbags for use in 1,000 Chevrolet Impala fleet cars for testing. The Olds Toronado rolling off production lines in 1974 was GM's first consumer car to be equipped with airbags, optional at a cost of $225. Among the problems facing GM in developing its airbags were: redesign of the car interior to accommodate airbags, unacceptably high sound levels, and test dummies lacking the variability to test for a range of car occupant sizes. Despite all those challenges, the airbags utilized in the seventies were in some ways superior to those now in use. They included adjustable inflators so that in less severe crashes, the airbags did not inflate as rapidly. They also included a driver knee restraint as well as torso airbag and a front passenger combination airbag that included cushioning for the torso and the knees. Despite those advanced features, the cars came only with lap belts— no shoulder belts.

As Ford and GM continued to test their airbags, they found that they performed well — but with airbag-equipped vehicles seven deaths occurred in accidents nonetheless and one, that of an unrestrained infant, was blamed on airbags. It didn't help, either, that in 1974 closely-held results from a Volvo study made their way into the U.S. debate about airbags. In that study two dozen baby pigs (roughly the same size and weight of children aged 3-6) were anesthetized, situated 4-6 inches from airbags, and strapped into cars going less than 25 mph. When the cars crashed, only three pigs escaped without serious injuries. Most succumbed from serious heart and lung damage.

Still, in 1974, GM (which enjoyed a competitive advantage over Ford in airbag production) began making some Cadillacs, Oldsmobiles, and Buicks with optional airbags. Edward Cole, GM president from 1969 to 1974, had initially wanted to test airbags in 150,000 cars but when the 1973 oil crisis came along and pumped gas prices sky high, it was hard to convince consumers to lay out more cash for safety features. After three years' experience with optional airbags and total sales of a little more than 10,000, GM reverted to type (claiming that safety didn't sell) and dropped the poorly-selling feature.

Ford, still smarting from its malfunctioning test airbags, threw their weight behind an alternate solution. Iacocca focused instead on an "interlock seat belt". Until drivers and front-seat passengers had buckled up, their cars wouldn't start. Of course, if drivers had groceries, building supplies, or their pet dog in the front seat, they, too, had to be buckled in before the car would start. Although NHTSA had mandated interlock seat belts for all 1974 model cars, it didn't take long for Congress to react to a steady stream of consumer complaints and pass legislation outlawing the interlock belts.

From that seat belt rebellion, Transportation Secretary William Coleman had learned to throttle back a little when introducing new safety measures. In 1976, saying airbags could save 12,000 lives a year, he proposed a test program to include airbags in 400,000 cars.

Only months thereafter, however, Carter took office and appointed Joan Claybrooke the Director of the NHTSA. She had different ideas. She cancelled the Coleman test plan and pushed hard for mandatory airbags. By June 1975, she had set a rule in place requiring car manufacturers to include passive restraint protection in all 1984 model passenger cars. Although industry testers warned airbags could actually harm smaller car occupants and a report from Charles J. Kahane, one of her own agency statisticians, stated that data did not support the claim that airbags could reduce frontal crash fatalities by 55%, Claybrooke pressed on. When, in 1979, the General Accounting Office also warned that airbags could injure out-of-position occupants and GM notified NHTSA it would not offer optional passenger airbags on its 1981 models (as originally planned) because of potential injury to unrestrained small children, Claybrooke persisted, saying the evidence was fragmentary and speculative. She saw saving multiple lives as outweighing the risk to small women (under 5'4") and children.

While the standoff between manufacturers and government regulators continued here, in Europe Mercedes-Benz and others were developing their airbag concepts. Mercedes-Benz began its work on airbags in 1967 but it was Professor Guntram Huber who took the lead in researching and perfecting their airbag. During the sixties and seventies he visited the U.S. a number of times, attending Congressional hearings and talking with safety regulators. The voices of German drivers, however, echoed those in the U.S. who weren't keen on airbags that made a lot of noise and smelled bad when they went off, nor did those drivers feel good about putting fireworks into a car's interior. Still, developers continued in the belief that airbags could be perfected. Mercedes was talking with American firms, largely because they had already developed considerable expertise. They got in touch with U.S. companies involved in missile technology to obtain sample gas generators even as they had a German chemical firm, Bayern Chemie, work on developing a similar German product. They also learned about discharged gas for missiles from the German military and they partnered with Bosch on development of a sensor. After the 1974 fatal accident in the U.S. involving the unrestrained infant occurred, many American researchers jumped right off the airbag bandwagon, halting research and development activity and leaving Mercedes pretty much on its own. In 1980 Mercedes introduced airbags as an option on the high-end S-class saloon— and they began to export their technology internationally. Their system used pre-tensioners on seat belts to reduce impact forces before the airbag deployed. For some of their 1985 models airbags were made standard equipment.

Once Carter was out of office and the anti-regulatory Reagan administration took hold, Transportation Secretary Drew Lewis, in 1981, delayed the passive restraint mandate by a year and tried to rescind the mandate completely. The Supreme Court, however, ruled against that notion. So, the Transportation Department gave manufacturers another way out, saying that if, within two years, a sufficient number of states passed laws requiring seat belt use, passive restraints would not be necessary. Car manufacturers lobbied states hard but maybe not hard enough; the numbers just weren't there two years later and the requirement for passive restraints stood. Reagan's second Transportation Secretary Elizabeth Dole did manage, in 1984, to extend the deadline another year, giving manufacturers until 1986 to phase in passive safety restraints. Then, in 1986 the NHTSA okayed auto makers to include only driver airbags through the 1990 model year— and followed that a year later with authorization to utilize driver-only airbags until the 1994 model year.

Car manufacturers began to get with the program. Though, in 1983, AMC had called the airbag "one of the most dangerously misunderstood devices" ever offered customers, their opposition did not stand long. Ford offered airbags on its 1984 Tempo and, by 1986, offered driver's side airbags on the Mercury Topaz, as well. GM started to take another look at adding airbags to its cars, too. And despite Lee Iacocca's 1984 assertion that the airbag solution was worse than the problem and, later in the eighties, railing against them in his autobiography, in 1988, Chrysler was first to offer airbags as standard equipment. "Who says you can't teach an old dog new tricks?," read the ads. So what changed Iacocca's mind? He claimed to have seen the light, acknowledging the airbag's value— but public concern with automotive safety may have been the larger game changer. Manufacturers worried that failure to provide airbags could result in lost sales. By 1989, Ford announced it would offer airbags in nine of its car lines. International manufacturers were delivering airbag systems, as well. Porsche's 1986 944 Turbo was the first car to come equipped with airbags standard for driver and front seat passenger. In 1987 the Japanese Honda Legend came with optional airbags and in 1989, Saab included airbags as standard equipment on its Turbo 900.

As manufacturers rallied to produce airbags, an outside group committed to establishing quality standards for seat belts changed its name to expand its interests to include airbags. Founded in 1965 as the American Seat Belt Council, in 1988 it became the Automotive Occupant Restraints Council. With New York in the lead, states also began to enact legislation requiring insurance companies to reduce annual insurance premiums for cars equipped with airbags.

In 1991, Congress passed legislation— the Intermodal Surface Transportation Efficiency Act— requiring that all new cars for sale in the United States be equipped with airbags for driver and front seat passenger by 1997. The same requirement kicked in for the 1999 model year of vans and light trucks. The die was cast.

Oh, there were still reports of accidents in which women and children were killed rather than restrained by airbags. And in October 1991 NHTSA's experts toured the Big Three to learn what they could about discoveries from accident reports where airbags had been in use. Chrysler and Ford said they were satisfied with those results and saw no need for design changes but GM was seriously concerned about the burst out force of the bags. GM assured the NHTSA experts, however, that it was on course to meet the 1997/8 NHTSA deadlines— with no changes. By 1992, most manufacturers had airbags on the driver side, airbags television commercials showed deploying as billowy clouds. By the mid-nineties manufacturers also offered airbags for the front passenger side, and vendors began offering after-market retrofits with the crash sensor in the steering wheel for many different earlier car models. The march to produce airbags continued.

But all was not well. Initial stubborn resistance to include airbags had meant a later rush to meet deadlines. Airbags had not been tested adequately and by 1996 the federal government acknowledged that airbags could kill women and children. Federal Motor Vehicle Safety standard (FMVSS) 208 set a minimum compliance standard requiring that manufacturers certify airbags would not injure 5'9" crash test dummies. While the minimum was intended as a floor, manufacturers took it as a ceiling. The government encouraged manufacturers to protect vehicle occupants of all shapes and sizes and to conduct tests when occupants were out of position, i.e., unbelted, sitting close to the dash, leaning up against the side window, etc. What testing was done confirmed the dangers to small-sized occupants. In fact, in the years since airbags have been in use— and despite the multiple lives they've saved— they have at time resulted in secondary injuries including abrasions, arm fractures, blindness, brain damage, even decapitations.

As a partial cure, in 1996, the NHTSA proposed new airbag warnings — posted on sun visors — began to promote "smart" airbags, and authorized depowering airbags via cut-off switches. In that regard, consumers were not authorized to disconnect airbags themselves but, with case-by-case NHTSA approval, car dealers and repair shops could do so. While the "smart" airbag idea was not then adopted, it offered several additional protections: inflation pressure would be reduced, and airbags would inflate with variable force depending upon the speed of the crash. With passage of the Transportation Equity Act [TEA 21] in 1998, however, Congress set goals for the NHTSA in regulating airbags to improve occupant protection for occupants of different sizes and to minimize the risk to infants and children. Over a three-year period beginning in September 2003, manufacturers were required to install "smart" airbags. New crash tests were required simulating different types of crashes and new, smaller crash test dummies were introduced to supplement standard crash test dummies.

Research and development continued and led to many improvements. There were higher deployment thresholds, i.e., crashes at speeds of less than 12 mph did not deploy airbags. "Second generation" airbags were introduced, so called because they used less propellant. Low-cost tethers were installed to keep airbags from intruding too far into the passenger compartment. Lighter materials were used in the airbags themselves. Adjustable (to accident forces) inflators were added. Though this presented the greatest challenge to manufacturers, better sensors were added, as well. Suppression systems were installed to ensure that those sitting in close proximity to an airbag (a short driver sitting close to the steering wheel or a passenger leaning over to pick something up from the floor) would not be injured when the airbag detonated. Weight sensors in seats or floor pans could determine if someone was too close to the airbag — or if the seat was empty — and prevent deployment. An alternate improvement came with "bias" flaps. If sensors detected someone was in the way of the deploying airbag, force deployed to the side instead of directly toward the passenger. Diagnostic modules were added that tested the readiness of the airbag system whenever the car was started, and lit indicators were added to ensure occupants that their airbag would deploy if circumstances necessitated that. Rather than continued reliance on sodium azide as a propellant, compressed air was used. These gas inflators were elongated cylinders and could be situated inside the instrument panel, door panel, or side pillars. Besides moving away from the toxic product (sodium azide), the compressed gas kept deployment temperatures lower, resolving an earlier issue with heat build-up that could set fire to trim.

In the 2000s, even on budget cars, more airbags began to appear — knee airbags, side curtain airbags, and rear airbags. Safety is increasingly important to buyers and these days it is common to see four or six airbag units in cars. In 2008, Toyota introduced the first rear curtain airbag (which inflates over the rear window) in its microcar iQ. Ford is advertising a number of new airbag features on its 2012 Focus. The driver-side airbag uses a new tether designed to pull in the lower section of the airbag that can provide additional protection to chest and ribs. Side airbags are vented, reducing pressure on smaller occupants, and there's an improved match between occupant size and deployment force. There is already an association for deciding whether and/or how to recycle airbags, too. It's the Automotive Recyclers Association and they're looking at safe, green ways to reuse airbags. As long as they are properly matched, handled, and installed, they should be safe.

The future of airbags surely includes innovations in a number of areas. Work is being done on a quasi-airbag for rear seat occupants wherein an airbag is incorporated into the shoulder belt and is deployed simultaneously with other airbags. Increased use will be made of infrared and ultrasonic sensing technology. Airbags will be lighter in weight and will be deployed by smaller, more integrated systems. There will be numerous variations in the way the bag is folded, how it is tethered and vented, and its deployment path. There will be rear seat airbags — built into the back of the front seat. Manufacturers will make model-specific videos available on YouTube so consumers can view the effectiveness of the airbags installed on their cars. There will be a kind of black box for cars that can capture information about the occupant, his position in the seat, proximity to the airbags, etc.

But whatever those advances are and whenever they appear, one thing is for sure. Airbags are saving lives. GM did a study in 1989 that showed combining lap/shoulder belts and airbags reduced driver fatalities by 46%. When the Insurance Institute for Highway Safety conducted a study of road accidents from 1985 to 1991, it found that fatalities in frontal collisions were 28% lower in cars with airbags. A State Farm Insurance Company study reported that drivers using both seat belts and airbags were 35% less likely to suffer serious crash injuries than drivers using only seat belts. The NHTSA estimates that airbags have saved one in six drivers and front passengers from deadly accidents. In 2010, the Department of Transportation announced that, due to numerous safety improvements, 2009 highway deaths had fallen to levels as low as those reported in 1954 — not bad, not bad at all.

Airbags for planes, bicycles, and motorcycles? They may be in our future.

In January 2011, the National Transportation Safety Board met to consider whether to recommend that airbags be installed in planes. The FAA approved the use of aviation airbags in 2003 and while half of general aviation planes (pretty much everything but military aircraft and commercial airline planes) sold today come with airbags, they represent less than a third of those planes registered in the U.S. The likeliest airbags to be used would be ones incorporated into seat belts, and though no such decision has been made, it's possible that these could begin to appear in helicopters or commercial airliners, as well.

Since 2006, two Swedish inventors have been working on the Hövding, a clever airbag helmet for cyclists. Worn around the neck like a scarf, it contains an airbag that inflates to hood the cyclist's head. If, say, a cyclist is clipped by a car, sensors register the cyclist's erratic movements and activate the release mechanism.

Motorcyclists can wear an airbag jacket or vest. The biker attaches a tether from the clothing to an anchor point on the bike. If the rider is suddenly ejected from the bike, a carbon dioxide cartridge deploys and inflates a bladder in the clothing. In 2005, though, Honda's Gold Wing was the first production motorcycle to include airbags. The airbag module is situated in front of the rider. Four crash sensors are attached on both sides of the front fork. If the on-board computer determines a frontal crash is imminent, the airbag is deployed.

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