Adaptive Airbag
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An airbag is a vehicle occupant-restraint system using a bag designed to inflate extremely quickly, then quickly deflate during a
collision In physics, a collision is any event in which two or more bodies exert forces on each other in a relatively short time. Although the most common use of the word ''collision'' refers to incidents in which two or more objects collide with great fo ...
. It consists of the airbag cushion, a flexible fabric bag, an inflation module, and an impact sensor. The purpose of the airbag is to provide a vehicle occupant with soft cushioning and restraint during a collision. It can reduce injuries between the flailing occupant and the interior of the vehicle. The airbag provides an energy-absorbing surface between the vehicle's occupants and a steering wheel, instrument panel, body pillar, headliner, and
windshield The windshield (North American English) or windscreen (Commonwealth English) of an aircraft, car, bus, motorbike, truck, train, boat or streetcar is the front window, which provides visibility while protecting occupants from the elements. Mo ...
. Modern
vehicle A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), wa ...
s may contain up to 10 airbag modules in various configurations, including: driver, passenger, side-curtain, seat-mounted, door-mounted, B and C-pillar mounted side-impact, knee bolster, inflatable seat belt, and pedestrian airbag modules. During a crash, the vehicle's crash sensors provide crucial information to the airbag electronic controller unit (ECU), including collision type, angle, and severity of impact. Using this information, the airbag ECU's crash algorithm determines if the crash event meets the criteria for deployment and triggers various firing circuits to deploy one or more airbag modules within the vehicle. Working as a supplemental restraint system to the vehicle's seat-belt systems, airbag module deployments are triggered through a
pyrotechnic Pyrotechnics is the science and craft of creating such things as fireworks, safety matches, oxygen candles, explosive bolts and other fasteners, parts of automotive airbags, as well as gas-pressure blasting in mining, quarrying, and demolition. ...
process that is designed to be used once. Newer side-impact airbag modules consist of compressed-air cylinders that are triggered in the event of a side-on vehicle impact. The first commercial designs were introduced in passenger automobiles during the 1970s, with limited success, and actually caused some fatalities. Broad commercial adoption of airbags occurred in many markets during the late 1980s and early 1990s. Many modern vehicles now include six or more units.


Active vs. passive safety

Airbags are considered "passive" restraints and act as a supplement to "active" restraints. Because no action by a vehicle occupant is required to activate or use the airbag, it is considered a "passive" device. This is in contrast to
seat belt A seat belt (also known as a safety belt, or spelled seatbelt) is a vehicle safety device designed to secure the driver or a passenger of a vehicle against harmful movement that may result during a collision or a sudden stop. A seat belt reduc ...
s, which are considered "active" devices because the vehicle occupant must act to enable them. This terminology is not related to active and passive safety, which are, respectively, systems designed to prevent collisions in the first place, and systems designed to minimize the effects of collisions once they occur. In this use, a car
antilock braking system An anti-lock braking system (ABS) is a automobile safety, safety anti-Skid (automobile), skid Brake, braking system used on aircraft and on land motor vehicle, vehicles, such as cars, motorcycles, trucks, and buses. ABS operates by preventing t ...
qualifies as an active-safety device, while both its seatbelts and airbags qualify as passive-safety devices. Further terminological confusion can arise from the fact that passive devices and systems—those requiring no input or action by the vehicle occupant—can operate independently in an active manner; an airbag is one such device. Vehicle safety professionals are generally careful in their use of language to avoid this sort of confusion, though
advertising Advertising is the practice and techniques employed to bring attention to a product or service. Advertising aims to put a product or service in the spotlight in hopes of drawing it attention from consumers. It is typically used to promote a ...
principles sometimes prevent such
semantic Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference, meaning, or truth. The term can be used to refer to subfields of several distinct disciplines, including philosophy, linguistics and comput ...
caution in the consumer marketing of safety features. Further confusing the terminology, the
aviation safety Aviation safety is the study and practice of managing risks in aviation. This includes preventing aviation accidents and incidents through research, educating air travel personnel, passengers and the general public, as well as the design of airc ...
community uses the terms "active" and "passive" in the ''opposite'' sense from the automotive industry.


History


Origins

The airbag "for the covering of aeroplane and other vehicle parts" traces its origins to a United States patent, submitted in 1919 by two dentists from
Birmingham Birmingham ( ) is a city and metropolitan borough in the metropolitan county of West Midlands in England. It is the second-largest city in the United Kingdom with a population of 1.145 million in the city proper, 2.92 million in the West ...
, Arthur Parrott & Harold Round and approved in 1920. Air-filled bladders were in use as early as 1951. The airbag specifically for automobile use is credited independently to the American John W. Hetrick, who filed for an airbag patent on 5 August 1952, that was granted #2,649,311 by the United States Patent Office on 18 August 1953. German engineer Walter Linderer, who filed German patent #896,312 on 6 October 1951, was issued on 12 November 1953, approximately three months after American John Hetrick. Hetrick and Linderer's airbags were both based on a compressed air system, either released by spring, bumper contact, or by the driver. Later research during the 1960s showed that compressed air could not inflate the mechanical airbags fast enough to ensure maximum safety, leading to the current chemical and electrical airbags. In patent applications, manufacturers sometimes use the term "inflatable occupant restraint systems". Hetrick was an
industrial engineer Industrial engineering is an engineering profession that is concerned with the optimization of complex processes, systems, or organizations by developing, improving and implementing integrated systems of people, money, knowledge, information a ...
and member of the
United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
. His airbag design, however, only came about when he combined his experiences working with navy
torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, su ...
es with his desire to protect his family on the road. Despite working with the major automobile manufacturers of his time, Hetrick was unable to attract investment. Although airbags are now required in every automobile sold in the United States, Hetrick's 1951 patent filing serves as an example of a "valuable" invention with little economic value to its inventor. Its first commercial use was not implemented until after the patent expired in 1971, at which point the airbag was installed in a few experimental
Ford Ford commonly refers to: * Ford Motor Company, an automobile manufacturer founded by Henry Ford * Ford (crossing), a shallow crossing on a river Ford may also refer to: Ford Motor Company * Henry Ford, founder of the Ford Motor Company * Ford F ...
cars. In 1964, a Japanese automobile engineer, Yasuzaburou Kobori (小堀保三郎), started developing an airbag "safety net" system. His design harnessed an explosive to inflate an airbag, for which he was later awarded patents in 14 countries. He died in 1975, before seeing widespread adoption of airbag systems. In 1967, a breakthrough in the development of airbag crash
sensor A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon. In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
s came when Allen K. Breed invented a ball-in-tube mechanism for crash detection. Under his system, an
electromechanical In engineering, electromechanics combines processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focuses on the interaction of electrical and mechanical systems as a whole and how the two systems ...
sensor with a steel ball attached to a tube by a
magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...
would inflate an airbag in under 30 milliseconds. A small explosion of sodium azide was used instead of compressed air during inflation for the first time. Breed Corporation then marketed this innovation to
Chrysler Stellantis North America (officially FCA US and formerly Chrysler ()) is one of the " Big Three" automobile manufacturers in the United States, headquartered in Auburn Hills, Michigan. It is the American subsidiary of the multinational automoti ...
. A similar "Auto-Ceptor" crash-restraint, developed by the Eaton, Yale & Towne company for Ford, was soon also offered as an automatic safety system in the United States, while the Italian Eaton-Livia company offered a variant with localized air cushions. In the early 1970s,
General Motors The General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. It is the largest automaker in the United States and ...
began offering cars equipped with airbags, initially in government fleet-purchased, 1973 Chevrolet Impala sedans. These cars came with a 1974-style Oldsmobile instrument panel and a special steering wheel that contained the driver-side air bag. Two of these cars were crash tested after 20 years and the airbags deployed perfectly. An early example of the air-bag cars survives as of 2009. GM's
Oldsmobile Toronado The Oldsmobile Toronado is a personal luxury car manufactured and marketed by the Oldsmobile division of General Motors from 1966 to 1992 over four generations. The Toronado was noted for its transaxle version of GM's Turbo-Hydramatic transmission ...
was the first domestic U.S. vehicle to include a passenger airbag. General Motors marketed its first airbag modules under the "Air Cushion Restraint System" name, or ACRS. The automaker discontinued the option for its 1977
model year The model year (sometimes abbreviated "MY") is a method of describing the version of a product which has been produced over multiple years. The model year may or may not be the same as the calendar year in which the product was manufactured. ...
, citing lack of consumer interest. Ford and GM then spent years
lobbying In politics, lobbying, persuasion or interest representation is the act of lawfully attempting to influence the actions, policies, or decisions of government officials, most often legislators or members of regulatory agency, regulatory agencie ...
against air-bag requirements, claiming that the devices were unfeasible and inappropriate. Chrysler made driver-side airbags standard on 1988–1989 models, but airbags did not become widespread in American cars until the early 1990s.


As a substitute to seat belts

Airbags for passenger cars were introduced in the United States in the 1970s. When seat-belt usage rates in the country were quite low compared to modern-day, Ford built experimental cars with airbags in 1971.
Allstate The Allstate Corporation is an American insurance company, headquartered in Northfield Township, Illinois, near Northbrook since 1967. Founded in 1931 as part of Sears, Roebuck and Co., it was spun off in 1993 but still partially owned by S ...
operated a fleet of 200
Mercury Monterey The Mercury Monterey is a series of full-size cars that were manufactured and marketed by the Mercury division of Ford from 1952 to 1974. Deriving its name from Monterey Bay, the Mercury Monterey served as the upscale version of the Mercury Cus ...
s and showed reliability of airbags as well as their operation in crash testing, which also was promoted by the insurance company in popular magazine advertisements. General Motors followed in 1973 using full-sized Chevrolet vehicles. The early fleet of experimental GM vehicles equipped with airbags experienced seven fatalities, one of which was later suspected to have been caused by the airbag. In 1974, GM made its ACRS system (which consisted of a padded lower dashboard and a passenger-side air bag) available as a regular production option (RPO code AR3) in full-sized Cadillac, Buick and Oldsmobile models. The GM cars from the 1970s equipped with ACRS had a driver-side airbag, a driver-side knee restraint,. The passenger-side airbag protected both front passengers, and unlike most modern systems, integrated a knee and torso cushion while also having a dual-stage deployment dictated by force of the impact. The cars equipped with ACRS had lap belts for all seating positions, but lacked shoulder belts. Shoulder belts were already mandatory in the United States on closed cars without airbags for the driver and outer front passenger, but GM chose to market its airbags as a substitute for shoulder belts. Prices for this option on Cadillac models were US$225 in 1974, $300 in 1975, and $340 in 1976 (US$ in dollars ). The early development of airbags coincided with international interest in automobile safety legislation. Some safety experts advocated a performance-based occupant-protection standard rather than one mandating a particular technical solution (which could rapidly become outdated and prove to not be a
cost-effective Cost-effectiveness analysis (CEA) is a form of economic analysis that compares the relative costs and outcomes (effects) of different courses of action. Cost-effectiveness analysis is distinct from cost–benefit analysis, which assigns a monetar ...
approach). Less emphasis was placed on other designs as countries successfully mandated seatbelt restrictions, however.


As a supplemental restraint system


Frontal airbag

The auto industry and research and regulatory communities have moved away from their initial view of the airbag as a seat-belt replacement, and the bags are now nominally designated as supplemental restraint systems (SRS) or supplemental inflatable restraints. In 1981,
Mercedes-Benz Mercedes-Benz (), commonly referred to as Mercedes and sometimes as Benz, is a German luxury and commercial vehicle automotive brand established in 1926. Mercedes-Benz AG (a Mercedes-Benz Group subsidiary established in 2019) is headquartere ...
introduced the airbag in
West Germany West Germany is the colloquial term used to indicate the Federal Republic of Germany (FRG; german: Bundesrepublik Deutschland , BRD) between its formation on 23 May 1949 and the German reunification through the accession of East Germany on 3 O ...
as an option on its flagship saloon model, S-Class (W126). In the Mercedes system, the sensors automatically tensioned the seat belts to reduce occupants' motion on impact and then deployed the airbag on impact. This integrated the seat belts and airbag into a restraint system, rather than the airbag being considered an alternative to the seat belt. In 1987, the
Porsche 944 The Porsche 944 is a sports car manufactured by German automobile manufacturer Porsche from 1982 until 1991. A front-engine, rear-wheel drive mid-level model based on the 924 platform, the 944 was available in coupé or cabriolet body styles, w ...
Turbo became the first car to have driver and passenger airbags as standard equipment. The Porsche 944 and 944S had this as an available option. The same year also had the first airbag in a Japanese car, the
Honda Legend :''Sections of this article are translated from Japanese Wikipedia''. The Honda Legend is a series of V6-engined executive cars/mid-size luxury sedans produced by Honda since 1985 which currently serves as its flagship vehicle. It is larger tha ...
. In 1988,
Chrysler Stellantis North America (officially FCA US and formerly Chrysler ()) is one of the " Big Three" automobile manufacturers in the United States, headquartered in Auburn Hills, Michigan. It is the American subsidiary of the multinational automoti ...
became the first United States automaker to fit a driver-side airbag as standard equipment, which was offered in six different models. The following year, Chrysler became the first US auto manufacturer to offer driver-side airbags in all its new passenger models. Chrysler also began featuring the air bags in advertisements showing how the devices had saved lives that helped the public know the value of them and safety became a selling advantage in the late 1980s. All versions of the
Chrysler minivans The Chrysler minivans are a series of minivans that have been produced and marketed by the American automaker Chrysler since the 1984 model year. Currently in its sixth generation, the model line is marketed worldwide, primarily in North Americ ...
came with airbags starting for the 1991 model year. In 1993, The Lincoln Motor Company boasted that all vehicles in their model line were equipped with dual airbags, one for driver-side and another for passenger-side. The 1993 Jeep Grand Cherokee became the first SUV to offer a driver-side airbag when it was launched in 1992. Driver and passenger airbags became standard equipment in all
Dodge Intrepid The Dodge Intrepid is a full sized front-wheel drive four-door sedan that was produced by Dodge for model years 1993 to 2004. It is related to the Chrysler 300M, Chrysler Concorde, Chrysler LHS, Chrysler New Yorker, and Eagle Vision which we ...
,
Eagle Vision The Eagle Vision is a full-sized, front-wheel drive four-door sports sedan produced from 1992 until 1997. It was marketed by Eagle, replacing the AMC/Renault-designed Eagle Premier (from which the Vision was derived). The Eagle Vision was bad ...
, and
Chrysler Concorde The Chrysler Concorde is a full-size, front wheel drive four-door sedan that was produced by Chrysler from 1992 to 2004. It assumed the C-body Chrysler New Yorker Salon's position as the entry-level full-size sedan in the Chrysler brand lin ...
sedans ahead of any safety regulations. Early 1993 saw the 4-millionth airbag-equipped Chrysler vehicle roll off the assembly line. In October 1993, the
Dodge Ram The Ram pickup (marketed as the Dodge Ram until 2010) is a full-size pickup truck manufactured by Stellantis North America (formerly Chrysler Group LLC and FCA US LLC) and marketed from 2010 onwards under the Ram Trucks brand. The current fi ...
became the first
pickup truck A pickup truck or pickup is a light-duty truck that has an enclosed cabin, and a back end made up of a cargo bed that is enclosed by three low walls with no roof (this cargo bed back end sometimes consists of a tailgate and removable covering) ...
with a standard driver-side airbag. The first known collision between two airbag-equipped automobiles took place on 12 March 1990 in
Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...
, USA. A 1989
Chrysler LeBaron The Chrysler LeBaron, also known as the Imperial LeBaron, is a line of automobiles built by Chrysler from 1931-1941 and from 1955-1995. The model was introduced in 1931, with a body manufactured by LeBaron Incorporated, LeBaron, and competed wit ...
crossed the
center line Center line, centre line or centerline may refer to: Sports * Center line, marked in red on an ice hockey rink * Centre line (football), a set of positions on an Australian rules football field * Centerline, a line that separates the service cour ...
and hit another 1989 Chrysler LeBaron in a
head-on collision A head-on collision is a traffic collision where the front ends of two vehicles such as cars, trains, ships or planes hit each other when travelling in opposite directions, as opposed to a side collision or rear-end collision. Rail transport ...
, causing both driver airbags to deploy. The drivers suffered only minor injuries despite extensive damage to the vehicles. The United States
Intermodal Surface Transportation Efficiency Act The Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA, pronounced ''Ice-Tea'') is a United States federal law that posed a major change to transportation planning and policy, as the first U.S. federal legislation on the subject in ...
of 1991 required passenger cars and light trucks built after 1 September 1998 to have airbags for the driver and the front passenger. In the United States, NHTSA estimated that airbags had saved over 4,600 lives by 1 September 1999; however, the crash deployment experience of the early 1990s installations indicated that some fatalities and serious injuries were in fact caused by airbags. In 1998, NHTSA initiated new rules for advanced airbags that gave automakers more flexibility in devising effective technological solutions. The revised rules also required improved protection for occupants of different sizes regardless of whether they use seat belts, while minimizing the risk to infants, children, and other occupants caused by airbags. In
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
, airbags were almost unheard of until the early 1990s. By 1991, four manufacturers – BMW,
Honda is a Japanese public multinational conglomerate manufacturer of automobiles, motorcycles, and power equipment, headquartered in Minato, Tokyo, Japan. Honda has been the world's largest motorcycle manufacturer since 1959, reaching a product ...
, Mercedes-Benz, and
Volvo The Volvo Group ( sv, Volvokoncernen; legally Aktiebolaget Volvo, shortened to AB Volvo, stylized as VOLVO) is a Swedish multinational manufacturing corporation headquartered in Gothenburg. While its core activity is the production, distributio ...
– offered the airbag on some of their higher-end models, but shortly afterward, airbags became a common feature on more mainstream cars, with
Ford Ford commonly refers to: * Ford Motor Company, an automobile manufacturer founded by Henry Ford * Ford (crossing), a shallow crossing on a river Ford may also refer to: Ford Motor Company * Henry Ford, founder of the Ford Motor Company * Ford F ...
and
Vauxhall Vauxhall ( ) is a district in South West London, part of the London Borough of Lambeth, England. Vauxhall was part of Surrey until 1889 when the County of London was created. Named after a medieval manor, "Fox Hall", it became well known for ...
/
Opel Opel Automobile GmbH (), usually shortened to Opel, is a German automobile manufacturer which has been a subsidiary of Stellantis since 16 January 2021. It was owned by the American automaker General Motors from 1929 until 2017 and the PSA Grou ...
among the manufacturers to introduce the airbag to its model ranges in 1992.
Citroën Citroën () is a French automobile brand. The "Automobiles Citroën" manufacturing company was founded in March 1919 by André Citroën. Citroën is owned by Stellantis since 2021 and previously was part of the PSA Group after Peugeot acquired ...
,
Fiat Fiat Automobiles S.p.A. (, , ; originally FIAT, it, Fabbrica Italiana Automobili di Torino, lit=Italian Automobiles Factory of Turin) is an Italian automobile manufacturer, formerly part of Fiat Chrysler Automobiles, and since 2021 a subsidiary ...
,
Nissan , trade name, trading as Nissan Motor Corporation and often shortened to Nissan, is a Japanese multinational corporation, multinational Automotive industry, automobile manufacturer headquartered in Nishi-ku, Yokohama, Japan. The company sells ...
,
Hyundai Hyundai is a South Korean industrial conglomerate ("chaebol"), which was restructured into the following groups: * Hyundai Group, parts of the former conglomerate which have not been divested ** Hyundai Mobis, Korean car parts company ** Hyundai ...
,
Peugeot Peugeot (, , ) is a French brand of automobiles owned by Stellantis. The family business that preceded the current Peugeot companies was founded in 1810, with a steel foundry that soon started making hand tools and kitchen equipment, and the ...
,
Renault Groupe Renault ( , , , also known as the Renault Group in English; legally Renault S.A.) is a French multinational automobile manufacturer established in 1899. The company produces a range of cars and vans, and in the past has manufactured ...
, and
Volkswagen Volkswagen (),English: , . abbreviated as VW (), is a German Automotive industry, motor vehicle manufacturer headquartered in Wolfsburg, Lower Saxony, Germany. Founded in 1937 by the German Labour Front under the Nazi Party and revived into a ...
followed shortly afterwards. By 1999, finding a new mass market car without an airbag at least as optional equipment was difficult, and some late 1990s products, such as the
Volkswagen Golf Mk4 The Volkswagen Golf Mk4 (or VW ''Type 1J'') is a compact car, the fourth generation of the Volkswagen Golf and the successor to the Volkswagen Golf Mk3. Launched in October 1997 for the 1998 model year, it was the best selling car in Europe in ...
, also featured side airbags. The
Peugeot 306 The Peugeot 306 is a small family car built by the French car manufacturer Peugeot from 1993 to 2002. It replaced the 309. Peugeot gave the 306 many updates and aesthetic changes to keep up with the competition, and it was replaced by the 307 in ...
is one example of the European automotive mass-market evolution: starting in early 1993, most of these models did not even offer a driver's airbag as an option, but by 1999, even side airbags were available on several variants.
Audi Audi AG () is a German automotive manufacturer of luxury vehicles headquartered in Ingolstadt, Bavaria, Germany. As a subsidiary of its parent company, the Volkswagen Group, Audi produces vehicles in nine production facilities worldwide. Th ...
was late to offer airbag systems on a broader scale, since even in the 1994 model year, its popular models did not offer airbags. Instead, the German automaker until then relied solely on its proprietary cable-based
procon-ten procon-ten (lower case initial ''"p"'') (an acronym for ''Programmed Contraction-Tension'') is a proprietary ''Safety Restraint System'' (SRS), used by German car manufacturer Audi from 1986 until the mid-1990s. Audi was one of the last German ...
restraint system. Variable force-deployment front airbags were developed to help minimize injury from the airbag itself. The emergence of the airbag has contributed to a sharp decline in the number of deaths and serious injuries on the roads of Europe since 1990, and by 2010, the number of cars on European roads lacking an airbag represented a very small percentage of cars, mostly the remaining cars dating from the mid-1990s or earlier. Many new cars in Latin America, including the
Kia Picanto The Kia Picanto is a city car that has been produced by the South Korean car manufacturer, Kia, since 2003. Other names of the car include Kia Morning ( ko, 기아 모닝, translit=Gia Moning) in South Korea, Hong Kong, Taiwan (first two generati ...
,
Kia Rio The Kia Rio ( ko, 기아 리오) is a subcompact car manufactured by Kia since November 1999 and now in its fourth generation. Body styles have included a three and five-door hatchback and four-door sedan, equipped with inline-four gasoline and d ...
,
Hyundai Accent The Hyundai Accent ( ko, 현대 엑센트), or Hyundai Verna (현대 베르나) is a subcompact car produced by Hyundai. In Australia, the first generation models carried over the Hyundai Excel name used by the Accent's predecessor. The Accent ...
, and
Suzuki Alto The is a kei car produced by Suzuki since 1979. The model, currently in its ninth generation, was first introduced in 1979 and has been built in many countries worldwide. The Alto originated as a commercial vehicle derivative of the Fronte, b ...
, are still regularly sold without airbags, as neither airbags nor
automatic braking A collision avoidance system (CAS), also known as a pre-crash system, forward collision warning system, or collision mitigation system, is an advanced driver-assistance system designed to prevent or reduce the severity of a collision. In its ...
systems in new cars are compulsory in Latin America.


= Shape of airbags

= The
Citroën C4 The Citroën C4 is a small family car/compact car (also classified as a compact crossover SUV since 2020) produced under their Citroën marque, from the French automaker PSA Group, and later Stellantis. It was positioned to be the successor to ...
provided the first "shaped" driver airbag, made possible by this car's unusual fixed-hub steering wheel. In 2019, Honda announced it would introduce a new front passenger airbag technology. Developed by
Autoliv Autoliv Inc. is a Swedish-American automotive safety supplier with sales to all leading car manufacturers worldwide. Together with its joint ventures, Autoliv has over 68,000 employees in 27 countries, of whom 5700 are involved in research, dev ...
and Honda R&D in
Ohio, United States Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...
, this new airbag design features three inflatable chambers connected across the front by a "noninflatable sail panel." The two outer chambers are larger than the middle chamber. When the airbag deploys, the sail panel cushions the occupant's head from the impact of hitting the airbag, and the three chambers hold the occupant's head in place, like a catcher's mitt. The goal of the tri-chamber airbag is to help "arrest high-speed movement" of the head, thereby reducing the likelihood of concussion injuries in a collision. The first vehicle to come with the tri-chamber airbag installed from the factory was in 2020 (for the 2021 model year) for the
Acura TLX The Acura TLX is a four-door entry-level luxury sedan sold by Acura, a luxury division of Honda, since 2014. It is the successor to both the TL and TSX models. As of 2021, the discontinuation of the RLX leaves the TLX as the flagship sedan in ...
. Honda hopes that the new technology will soon make its way to all vehicles.


= Rear airbag

= Mercedes began offering rear passengers protection in frontal collisions in September 2020 (for the 2021 model year) for the
Mercedes-Benz S-Class (W223) The Mercedes-Benz W223 is the seventh generation of the S-Class produced by Mercedes-Benz since 2020. It replaces the W222 S-Class which has been produced since 2013. The W223 S-Class was unveiled on 2 September 2020. Development and launch T ...
.


Side airbag

Essentially, two types of side airbags are commonly used today - the side-torso airbag and the side-curtain airbag. More recently, center airbags are becoming more common in the European market. Most vehicles equipped with side-curtain airbags also include side-torso airbags. However, some, such as the
Chevrolet Cobalt The Chevrolet Cobalt is a compact car introduced by Chevrolet in 2004 for the 2005 model year. The Cobalt replaced both the Cavalier and the Toyota-based Geo/Chevrolet Prizm as Chevrolet's compact car. The Cobalt was available as both a coupe a ...
, 2007–09 model Chevrolet Silverado/GMC Sierra, and 2009–12
Dodge Ram The Ram pickup (marketed as the Dodge Ram until 2010) is a full-size pickup truck manufactured by Stellantis North America (formerly Chrysler Group LLC and FCA US LLC) and marketed from 2010 onwards under the Ram Trucks brand. The current fi ...
do not feature the side-torso airbag. From around 2000, side-impact airbags became commonplace on even low- to mid-range vehicles, such as the smaller-engined versions of the
Ford Fiesta The Ford Fiesta is a supermini car marketed by Ford since 1976 over seven generations. Over the years, the Fiesta has mainly been developed and manufactured by Ford's European operations, and has been positioned below the Escort (later the ...
and
Peugeot 206 The Peugeot 206 is a supermini car (B-segment) designed and produced by the French car manufacturer Peugeot since May 1998 as a replacement to the Peugeot 205. Developed under the codename ''T1'', it was released in September 1998 in hatchback fo ...
, and curtain airbags were also becoming regular features on mass-market cars. The
Toyota Avensis The is a mid-size/ large family car built in Derbyshire, United Kingdom by the Japanese automaker Toyota from October 1997 to August 2018. It was the direct successor to the European Carina E and was available as a four-door saloon, five-door l ...
, launched in 2003, was the first mass-market car to be sold in Europe with nine airbags.


= Side torso airbag

= Side-impact airbags or side-torso airbags are a category of airbags usually located in the seat or door panel, and inflate between the seat occupant and the door. These airbags are designed to reduce the risk of injury to the pelvic and lower abdomen regions. Most vehicles are now being equipped with different types of designs, to help reduce injury and ejection from the vehicle in rollover crashes. More recent side-airbag designs include a two chamber system; a firmer lower chamber for the pelvic region and softer upper chamber for the ribcage. Swedish company Autoliv AB was granted a patent on side-impact airbags, and they were first offered as an option in 1994 on the 1995
Volvo 850 The Volvo 850 is a compact executive car that was produced by the Swedish manufacturer Volvo Cars from 1991 until 1996. Designed by Jan Wilsgaard, the car was introduced in a saloon body style; an estate style was introduced in 1993. The Volvo ...
, and as standard equipment on all Volvo cars made after 1995. In 1997,
Saab Saab or SAAB may refer to: Brands and enterprises * Saab Group, a Swedish aerospace and defence company, formerly known as SAAB, and later as Saab AB ** Datasaab, a former computer company, started as spin off from Saab AB * Saab Automobile, a fo ...
introduced the first combined head and torso airbags with the launch of the
Saab 9-5 The Saab 9-5 is an executive car that was produced by the Swedish automobile maker Saab from 1997 to 2012. The first generation 9-5 was introduced in 1997 for the 1998 model year, as the replacement to the Saab 9000. At the time, the car repres ...
. Some cars, such as the 2010 Volkswagen Polo Mk.5 have combined head- and torso-side airbags. These are fitted in the backrest of the front seats, and protect the head and the torso.


= Side tubular or curtain airbag

= In 1997, the
BMW 7 Series The BMW 7 Series is a full-size luxury sedan manufactured and marketed by the German automaker BMW since 1977. It is the successor to the BMW E3 "New Six" sedan and is now in its seventh generation. The 7 Series is BMW's flagship car and is on ...
and
5 Series The BMW 5 Series is an executive car manufactured and marketed by BMW since 1972, succeeding the New Class Sedans, and currently in its seventh generation. The 5 Series was initially available as a sedan, with a wagon/estate body style (market ...
were fitted with tubular-shaped head side airbags (inflatable tubular structure), the "Head Protection System (HPS)" as standard equipment. This airbag was designed to offer head protection in side impact collisions and also maintained inflation for up to seven seconds for rollover protection. However, this tubular-shaped airbag design has been quickly replaced by an inflatable 'curtain' airbag. In May 1998, Toyota began offering a side-curtain airbag deploying from the roof on the Progrés. In 1998, the
Volvo S80 The Volvo S80 is an executive car produced by the Swedish manufacturer Volvo Cars from 1998 to 2016 across two generations. It took the place of the rear-wheel-drive S90 as Volvo's flagship sedan. The first generation (1998–2006) was made a ...
was given roof-mounted curtain airbags to protect both front and rear passengers. Curtain airbags were then made standard equipment on all new Volvo cars from 2000 except for the first-generation C70, which received an enlarged side-torso airbag that also protects the head of front-seat occupants. The second-generation C70 convertible received the world's first door-mounted, side-curtain airbags that deployed upwards. Curtain airbags have been said to reduce brain injury or fatalities by up to 45% in a side impact with an SUV. These airbags come in various forms (e.g., tubular, curtain, door-mounted) depending on the needs of the application. Many recent
SUVs A sport utility vehicle (SUV) is a car classification that combines elements of road-going passenger cars with features from off-road vehicles, such as raised ground clearance and four-wheel drive. There is no commonly agreed-upon definitio ...
and MPVs have a long inflatable curtain airbag that protects all rows of seats. In many vehicles, the curtain airbags are programmed to deploy during some/all frontal impacts to manage passenger kinetics (e.g. head hitting B-pillar on the rebound), especially in offset crashes such as the IIHS's small overlap crash test.


Roll-sensing curtain airbag (RSCA)

Roll-sensing curtain airbags are designed to stay inflated for a longer duration of time, cover a larger proportion of the window, and be deployed in a roll-over crash. They offer protection to occupants' heads and help to prevent ejection. SUVs and pickups are more likely to be equipped with RSCAs due to their higher probability of rolling over and often a switch can disable the feature in case the driver wants to take the vehicle off-road.


= Center airbag

= In 2009, Toyota developed the first production rear-seat center airbag designed to reduce the severity of secondary injuries to rear passengers in a side collision. This system deploys from the rear center seat first appearing in on the
Crown Majesta The is a full-size luxury sedan from Toyota. It is an upmarket variant of the Crown and serves as Toyota's flagship model in various countries. The Crown Majesta appeared after the international introduction of the Celsior/Lexus LS in late 1 ...
. In late 2012, General Motors with supplier Takata introduced a front center airbag; it deploys from the driver's seat.
Hyundai Motor Group The Hyundai Motor Group (HMG; ; ; stylized as HYUΠDAI) is a South Korean '' chaebol'' (loosely similar to a multinational conglomerate but without a central holding company or ownership structure) headquartered in Seoul, South Korea. The HM ...
announced its development of center side airbag on September 18, 2019 installed inside the driver’s seat. Some
Volkswagen Volkswagen (),English: , . abbreviated as VW (), is a German Automotive industry, motor vehicle manufacturer headquartered in Wolfsburg, Lower Saxony, Germany. Founded in 1937 by the German Labour Front under the Nazi Party and revived into a ...
vehicles in 2022 equipped with center airbags include the ID.3 and the
Golf Golf is a club-and-ball sport in which players use various clubs to hit balls into a series of holes on a course in as few strokes as possible. Golf, unlike most ball games, cannot and does not use a standardized playing area, and coping wi ...
. The
Polestar 2 The Polestar 2 is a battery electric 5-door liftback produced by the Swedish automaker Volvo under its Polestar sub-brand. Based on the CMA platform, production began in March 2020 at the Luqiao CMA Super Factory in Luqiao, Zhejiang, China. ...
also includes a center airbag. With EuroNCAP updating its testing guidelines in 2020, European and Australian market vehicles increasingly use front center airbags, rear torso airbags and rear seatbelt pretensioners.


Knee airbag

The second driver-side and separate knee airbag was used in the
Kia Sportage The Kia Sportage is a lineup of sport utility vehicles manufactured by the South Korean manufacturer Kia since 1993. Since 2004, the Sportage has been categorized as a compact crossover SUV, while previously it occupied the compact SUV class. It ...
SUV and has been standard equipment since then. The airbag is located beneath the steering wheel. The
Toyota Caldina The is an automobile manufactured by Toyota for the Japanese market from 1992 to 2007. It replaced the Corona and Carina wagons, and was sold at ''Toyota Store'' and ''Toyopet Store'' locations in Japan. While the Caldina has never been official ...
introduced the first driver-side SRS knee airbag on the Japanese market in 2002.
Toyota Avensis The is a mid-size/ large family car built in Derbyshire, United Kingdom by the Japanese automaker Toyota from October 1997 to August 2018. It was the direct successor to the European Carina E and was available as a four-door saloon, five-door l ...
became the first vehicle sold in Europe equipped with a driver's knee airbag. The
EuroNCAP The European New Car Assessment Programme (Euro NCAP) is a European voluntary car safety performance assessment programme (i.e. a New Car Assessment Program) based in Leuven (Belgium) formed in 1996, with the first results released in February ...
reported on the 2003 Avensis, "There has been much effort to protect the driver's knees and legs and a knee airbag worked well." Since then certain models have also included front-passenger knee airbags, which deploy near or over the
glove compartment A glove compartment or glove box is a compartment built into the dashboard of an automobile, located over the front-seat passenger's footwell, and often used for miscellaneous storage. The name derives from the original purpose of the compart ...
in a crash. Knee airbags are designed to reduce leg injury. The knee airbag has become increasingly common from 2000.


Rear curtain airbag

In 2008, the new Toyota iQ microcar featured the first production rear-curtain shield airbag to protect the rear occupants' heads in the event of a rear-end impact.


Seat cushion airbag

Another feature of the Toyota iQ was a seat-cushion airbag in the passenger seat to prevent the pelvis from diving below the lap belt during a frontal impact or submarining. Later Toyota models such as the Yaris added the feature to the driver's seat, as well.


Seat-belt airbag

The seat-belt airbag is designed to better distribute the forces experienced by a buckled person in a crash by means of an increased seat belt area. This is done to reduce possible injuries to the rib cage or chest of the belt wearer. *2010:
Ford Explorer The Ford Explorer is a range of SUVs manufactured by Ford Motor Company since the 1991 model year. The first four-door SUV produced by Ford, the Explorer was introduced as a replacement for the two-door Bronco II. Within the current Ford light ...
and 2013
Ford Flex The Ford Flex is a full-size crossover SUV or wagon that was manufactured by the Ford Motor Company; a single generation was produced from the 2009 to 2019 model years. Introduced as the successor to the Ford Taurus X, the model line also funct ...
: optional rear seat belt airbags; standard on the 2013
Lincoln MKT The Lincoln MKT is a full-size 3-row luxury crossover SUV that was marketed by the Lincoln Motor Company, Lincoln division of Ford Motor Company; a single generation was produced from the 2010 to the 2019 model years. Slotted between the Lincoln ...
*2010:
Lexus LFA The is a two-seat sports car manufactured by Lexus, the luxury car division of Toyota. It is the second model in the Lexus F, F marque line of performance vehicles from Lexus, following the Lexus IS F, IS F, and also the first standalone Lexus ...
had seat belt airbags for driver and passenger *2013:
Mercedes-Benz S-Class (W222) The Mercedes-Benz W222 is the sixth generation of the S-Class produced from 2013 to 2020, the successor of the W221 S-Class and the predecessor of the W223 S-Class. The W222 was designed during 2009. The original design proposal of the car wa ...
has rear seat ''beltbags'' *2014: Ford Mondeo Mk IV has optional rear seat belt airbags for the two outer seats
Cessna Aircraft Cessna () is an American brand of general aviation aircraft owned by Textron Aviation since 2014, headquartered in Wichita, Kansas. Originally, it was a brand of the Cessna Aircraft Company, an American general aviation aircraft manufacturing c ...
also introduced seat belt airbags. They are as of 2003 standard on the 172, 182, and 206.


Pedestrian airbag

Airbag(s) mounted to the exterior of vehicles, so called ''pedestrian airbags'', are designed to reduce injuries in the event of a vehicle to pedestrian collision. When a collision is detected the airbag will deploy and cover hard areas, such as a-pillars and bonnet edges, before they can be struck by the pedestrian. When introduced in 2012 the Volvo V40 included the world's first pedestrian airbag as standard. As a result, the V40 ranked highest (88%) in the EuroNCAP's pedestrian tests. The 2014 Land Rover Discovery was fitted with a pedestrian airbag as well.


Manufacturers

SRS airbag suppliers include
Autoliv Autoliv Inc. is a Swedish-American automotive safety supplier with sales to all leading car manufacturers worldwide. Together with its joint ventures, Autoliv has over 68,000 employees in 27 countries, of whom 5700 are involved in research, dev ...
,
Daicel is a chemical company based in Japan. It operates business in celluloid technologies, organic chemicals, high-performance chemicals, polymers and pyrotechnic devices. The company's products include cellulose acetate, tow for cigarette filters, ...
, TRW and JSS (which now owns Breed, Key Safety Systems and Takata). The majority of impact sensors of airbags are manufactured by the
Lanka Harness Company Lanka (, ) is the name given in Hindu epics to the island fortress capital of the legendary asura king Ravana in the epics of the ''Ramayana'' and the ''Mahabharata''. The fortress was situated on a plateau between three mountain peaks known ...
.


Operation

The airbags in the vehicle are controlled by a central airbag control unit (ACU), a specific type of ECU. The ACU monitors a number of related sensors within the vehicle, including
accelerometers An accelerometer is a tool that measures proper acceleration. Proper acceleration is the acceleration (the rate of change of velocity) of a body in its own instantaneous rest frame; this is different from coordinate acceleration, which is accele ...
, impact sensors, side (door) pressure sensors,
wheel speed sensor A wheel speed sensor (WSS) or vehicle speed sensor (VSS) is a type of tachometer. It is a sender device used for reading the speed of a vehicle's wheel rotation. It usually consists of a toothed ring and pickup. Automotive wheel speed sensor ...
s,
gyroscope A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rota ...
s, brake pressure sensors, and seat occupancy sensors. Oftentimes, ACUs log this—and other—sensor data in a circular buffer and record it to onboard non-volatile memory, in order to provide a snapshot of the crash event for investigators. As such, an ACU frequently functions as the vehicle's
event data recorder An event data recorder (EDR), more specifically motor vehicle event data recorder (MVEDR), similar to an accident data recorder (ADR) sometimes referred to informally as an automotive black box (by analogy with the common nickname for flight reco ...
; not all EDRs are ACUs, and not all ACUs include EDR features. An ACU typically includes capacitors within its circuitry, so that the module remains powered and able to deploy the airbags in the event that the vehicle's battery connection to the ACU is severed during a crash. The bag itself and its inflation mechanism is concealed within the steering wheel boss (for the driver), or the dashboard (for the front passenger), behind plastic flaps or doors which are designed to tear open under the force of the bag inflating. Once the requisite threshold has been reached or exceeded, the airbag control unit will trigger the ignition of a
gas generator A gas generator is a device for generating gas. A gas generator may create gas by a chemical reaction or from a solid or liquid source, when storing a pressurized gas is undesirable or impractical. The term often refers to a device that uses a ...
propellant to rapidly inflate a fabric bag. As the vehicle occupant collides with and squeezes the bag, the gas escapes in a controlled manner through small vent holes. The airbag's volume and the size of the vents in the bag are tailored to each vehicle type, to spread out the deceleration of (and thus force experienced by) the occupant over time and over the occupant's body, compared to a seat belt alone. The signals from the various sensors are fed into the airbag control unit, which determines from them the angle of impact, the severity, or the force of the crash, along with other variables. Depending on the result of these calculations, the ACU may also deploy various additional restraint devices, such as
seat belt A seat belt (also known as a safety belt, or spelled seatbelt) is a vehicle safety device designed to secure the driver or a passenger of a vehicle against harmful movement that may result during a collision or a sudden stop. A seat belt reduc ...
pre-tensioners, and/or airbags (including frontal bags for driver and front passenger, along with seat-mounted side bags, and "curtain" airbags which cover the side glass). Each restraint device is typically activated with one or more
pyrotechnic Pyrotechnics is the science and craft of creating such things as fireworks, safety matches, oxygen candles, explosive bolts and other fasteners, parts of automotive airbags, as well as gas-pressure blasting in mining, quarrying, and demolition. ...
devices, commonly called an initiator or
electric match An electric match is a device that uses an externally applied electric current to ignite a combustible compound. Electric matches use a bridgewire consisting of a heating element to ignite a pyrogen, which is a quantity of readily ignited pyrotec ...
. The electric match, which consists of an electrical conductor wrapped in a combustible material, activates with a current pulse between 1 and 3 amperes in less than 2 milliseconds. When the conductor becomes hot enough, it ignites the combustible material, which initiates the gas generator. In a seat belt pre-tensioner, this hot gas is used to drive a piston that pulls the slack out of the seat belt. In an airbag, the initiator is used to ignite solid propellant inside the airbag inflator. The burning propellant generates inert gas which rapidly inflates the airbag in approximately 20 to 30 milliseconds. An airbag must inflate quickly in order to be fully inflated by the time the forward-traveling occupant reaches its outer surface. Typically, the decision to deploy an airbag in a frontal crash is made within 15 to 30 milliseconds after the onset of the crash, and both the driver and passenger airbags are fully inflated within approximately 60–80 milliseconds after the first moment of vehicle contact. If an airbag deploys too late or too slowly, the risk of occupant injury from contact with the inflating airbag may increase. Since more distance typically exists between the passenger and the instrument panel, the passenger airbag is larger and requires more gas to fill it. Older airbag systems contained a mixture of sodium azide (NaN3), KNO3, and SiO2. A typical driver-side airbag contains approximately 50–80 g of NaN3, with the larger passenger-side airbag containing about 250 g. Within about 40 milliseconds of impact, all these components react in three separate reactions that produce nitrogen gas. The reactions, in order, are as follows. # 2 NaN3 → 2 Na + 3 N2 (g) # 10 Na + 2 KNO3 → K2O + 5 Na2O + N2 (g) # K2O + Na2O + 2 SiO2 → K2SiO3 + Na2SiO3 The first two reactions create 4 molar equivalents of nitrogen gas, and the third converts the remaining reactants to relatively inert
potassium silicate Potassium silicate is the name for a family of inorganic compounds. The most common potassium silicate has the formula K2SiO3, samples of which contain varying amounts of water. These are white solids or colorless solutions.Gerard Lagaly, Werner ...
and
sodium silicate Sodium silicate is a generic name for chemical compounds with the formula or ·, such as sodium metasilicate , sodium orthosilicate , and sodium pyrosilicate . The anions are often polymeric. These compounds are generally colorless transparent ...
. The reason that KNO3 is used rather than something like NaNO3 is because it is less hygroscopic. It is very important that the materials used in this reaction are not hygroscopic because absorbed moisture can de-sensitize the system and cause the reaction to fail. The particle size of the initial reactants is important to reliable operation. The NaN3 and KNO3 must be between 10 and 20 
µm The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...
, while the SiO2 must be between 5 and 10 µm. There are ongoing efforts to find alternative compounds that can be used in airbags which have less toxic reactants. In a journal article by Akiyoshi et al., it was found that for the reaction of the Sr complex nitrate, (Sr(NH2NHCONHNH2)∙(NO3)2) of carbohydrazide (SrCDH) with various oxidizing agents resulted in the evolution of N2 and CO2 gases. Using KBrO3 as the oxidizing agent resulted in the most vigorous reaction as well as the lowest initial temperature of the reaction. The N2 and CO2 gases evolved made up 99% of all gases evolved. Nearly all the starting materials won't decompose until reaching temperatures of 500 °C or higher so this could be a viable option as an airbag gas generator. In a patent containing another plausible alternative to NaN3 driven airbags, the gas generating materials involved the use of
guanidine nitrate Guanidine nitrate is the chemical compound with the formula (NH2)3O3. It is a colorless, water-soluble salt. It is produced on a large scale and finds use as precursor for nitroguanidine, fuel in pyrotechnics and gas generators. Its correct n ...
, 5-aminotetrazole, bitetrazole dihydrate,
nitroimidazole 5-Nitroimidazole is an organic compound with the formula O2NC3H2N2H. The nitro group at position 5 on the imidazole ring is the most common positional isomer. The term nitroimidazole also refers to a class of antibiotics that share similar chemi ...
, and basic
copper nitrate Copper(II) nitrate describes any member of the family of inorganic compounds with the formula Cu( NO3)2(H2O)x. The hydrates are blue solids. Anhydrous copper nitrate forms blue-green crystals and sublimes in a vacuum at 150-200 °C. Common ...
. It was found that these non-azide reagents allowed for a less toxic, lower combustion temperature reaction, and more easily disposable airbag inflation system. Front airbags normally do not protect the occupants during side, rear, or rollover collisions. Since airbags deploy only once and deflate quickly after the initial impact, they will not be beneficial during a subsequent collision. Safety belts help reduce the risk of injury in many types of crashes. They help to properly position occupants to maximize the airbag's benefits and they help restrain occupants during the initial and any following collisions. In vehicles equipped with a rollover sensing system, accelerometers and gyroscopes are used to sense the onset of a rollover event. If a rollover event is determined to be imminent, side-curtain airbags are deployed to help protect the occupant from contact with the side of the vehicle interior, and also to help prevent occupant ejection as the vehicle rolls over.


Triggering conditions

Airbags are designed to deploy in frontal and near-frontal collisions more severe than a threshold defined by the regulations governing vehicle construction in whatever particular market the vehicle is intended for: United States regulations require deployment in crashes at least equivalent in deceleration to a 23 km/h (14 mph) barrier collision, or similarly, striking a parked car of similar size across the full front of each vehicle at about twice the speed. International regulations are performance-based, rather than technology-based, so airbag deployment threshold is a function of overall vehicle design. Unlike
crash test A crash test is a form of destructive testing usually performed in order to ensure safe design standards in crashworthiness and crash compatibility for various modes of transportation (see automobile safety) or related systems and componen ...
s into barriers, real-world crashes typically occur at angles other than directly into the front of the vehicle, and the crash forces usually are not evenly distributed across the front of the vehicle. Consequently, the relative speed between a striking and struck vehicle required to deploy the airbag in a real-world crash can be much higher than an equivalent barrier crash. Because airbag sensors measure deceleration, the vehicle speed is not a good indicator of whether an airbag should have deployed. Airbags can deploy due to the vehicle's undercarriage striking a low object protruding above the roadway due to the resulting deceleration. The airbag sensor is a
MEMS Microelectromechanical systems (MEMS), also written as micro-electro-mechanical systems (or microelectronic and microelectromechanical systems) and the related micromechatronics and microsystems constitute the technology of microscopic devices, ...
accelerometer An accelerometer is a tool that measures proper acceleration. Proper acceleration is the acceleration (the rate of change of velocity) of a body in its own instantaneous rest frame; this is different from coordinate acceleration, which is accele ...
, which is a small
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
with integrated micro mechanical elements. The microscopic mechanical element moves in response to rapid deceleration, and this motion causes a change in capacitance, which is detected by the electronics on the chip that then sends a signal to fire the airbag. The most common MEMS accelerometer in use is the ADXL-50 by
Analog Devices Analog Devices, Inc. (ADI), also known simply as Analog, is an American multinational semiconductor company specializing in data conversion, signal processing and power management technology, headquartered in Wilmington, Massachusetts. The co ...
, but there are other MEMS manufacturers as well. Initial attempts using
mercury switch A mercury switch is an electrical switch that opens and closes a circuit when a small amount of the liquid metal mercury connects metal electrodes to close the circuit. There are several different basic designs (tilt, displacement, radial, etc. ...
es did not work well. Before MEMS, the primary system used to deploy airbags was called a "
rolamite Rolamite is a technology for very low friction bearings developed by Sandia National Laboratories in the 1960s. It is the only elementary machine discovered in the twentieth century and can be used in various ways such as a component in switches, ...
". A rolamite is a mechanical device, consisting of a roller suspended within a tensioned band. As a result of the particular geometry and material properties used, the roller is free to translate with little
friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of t ...
or
hysteresis Hysteresis is the dependence of the state of a system on its history. For example, a magnet may have more than one possible magnetic moment in a given magnetic field, depending on how the field changed in the past. Plots of a single component of ...
. This device was developed at
Sandia National Laboratories Sandia National Laboratories (SNL), also known as Sandia, is one of three research and development laboratories of the United States Department of Energy's National Nuclear Security Administration (NNSA). Headquartered in Kirtland Air Force Ba ...
. The rolamite, and similar macro-mechanical devices were used in airbags until the mid-1990s when they were universally replaced with MEMS. Nearly all airbags are designed to automatically deploy in the event of a vehicle fire when temperatures reach 150–200 °C (300–400 °F). This safety feature, often termed auto-ignition, helps to ensure that such temperatures do not cause an explosion of the entire airbag module. Today, airbag triggering
algorithms In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing c ...
are becoming much more complex. They try to reduce unnecessary deployments and adapt the deployment speed to the crash conditions. The algorithms are considered valuable
intellectual property Intellectual property (IP) is a category of property that includes intangible creations of the human intellect. There are many types of intellectual property, and some countries recognize more than others. The best-known types are patents, cop ...
. Experimental algorithms may take into account such factors as the weight of the occupant, the seat location, seatbelt use, and even attempt to determine if a
baby seat An infant or baby is the very young offspring of human beings. ''Infant'' (from the Latin word ''infans'', meaning 'unable to speak' or 'speechless') is a formal or specialised synonym for the common term ''baby''. The terms may also be used to ...
is present.


Inflation

When the frontal airbags are to deploy, a signal is sent to the inflator unit within the airbag control unit. An igniter starts a rapid
chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...
generating primarily
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
gas (N2) to fill the airbag making it deploy through the module cover. Some airbag technologies use compressed
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
or
argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...
gas with a pyrotechnic operated valve ("hybrid gas generator"), while other technologies use various energetic
propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...
s. Although propellants containing the highly toxic sodium azide (NaN3) were common in early inflator designs, little to no toxic sodium azide has been found on used airbags. The azide-containing pyrotechnic gas generators contain a substantial amount of the propellant. The driver-side airbag would contain a canister containing about 50 grams of sodium azide. The passenger side container holds about 200 grams of sodium azide. The alternative propellants may incorporate, for example, a combination of
nitroguanidine Nitroguanidine - sometimes abbreviated NGu - is a colorless, crystalline solid that melts at 257 °C and decomposes at 254 °C. Nitroguanidine is an extremely insensitive but powerful high explosive. Wetting it with > 20 wt.-% water effe ...
, phase-stabilized
ammonium nitrate Ammonium nitrate is a chemical compound with the chemical formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is ...
(NH4NO3) or other nonmetallic oxidizer, and a nitrogen-rich fuel different from azide (e.g.
tetrazole Tetrazoles are a class of synthetic organic heterocyclic compound, consisting of a 5-member ring of four nitrogen atoms and one carbon atom. The name tetrazole also refers to the parent compound with formula CH2N4, of which three isomers can be f ...
s,
triazole A triazole is a heterocyclic compound featuring a five-membered ring of two carbon atoms and three nitrogen atoms with molecular formula C2H3N3. Triazoles exhibit substantial isomerism, depending on the positioning of the nitrogen atoms within t ...
s, and their salts). The burn rate modifiers in the mixture may be an alkaline metal
nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
(NO3-) or
nitrite The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...
(NO2-),
dicyanamide Dicyanamide, also known as dicyanamine, is an anion having the formula . It contains two cyanide groups bound to a central nitrogen anion. The chemical is formed by decomposition of 2-cyanoguanidine. It is used extensively as a counterion of org ...
or its salts,
sodium borohydride Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, is an inorganic compound with the formula Na BH4. This white solid, usually encountered as an aqueous basic solution, is a reducing agent that finds appli ...
(NaBH4), etc. The coolants and
slag Slag is a by-product of smelting (pyrometallurgical) ores and used metals. Broadly, it can be classified as ferrous (by-products of processing iron and steel), ferroalloy (by-product of ferroalloy production) or non-ferrous/base metals (by-prod ...
formers may be e.g.
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...
,
silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
, alumina, glass, etc. Other alternatives are e.g.
nitrocellulose Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and ...
based propellants (which have high gas yield but bad storage stability, and their
oxygen balance Oxygen balance (OB, OB%, or Ω) is an expression that is used to indicate the degree to which an explosive can be oxidized. If an explosive molecule contains just enough oxygen to fully oxidize the other atoms in the explosive. For example, fully ...
requires secondary oxidation of the reaction products to avoid buildup of carbon monoxide), or high-oxygen nitrogen-free organic compounds with inorganic oxidizers (e.g., di or tri
carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...
s with
chlorate The chlorate anion has the formula ClO3-. In this case, the chlorine atom is in the +5 oxidation state. "Chlorate" can also refer to chemical compounds containing this anion; chlorates are the salts of chloric acid. "Chlorate", when followed by ...
s (ClO3-) or
perchlorate A perchlorate is a chemical compound containing the perchlorate ion, . The majority of perchlorates are commercially produced salts. They are mainly used as oxidizers for pyrotechnic devices and to control static electricity in food packaging. Per ...
s (ClO4-) and eventually metallic oxides; the nitrogen-free formulation avoids formation of toxic
nitrogen oxide Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds: Charge-neutral *Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide *Nitrogen dioxide (), nitrogen(IV) oxide * Nitrogen trioxide (), or n ...
s). From the onset of the crash, the entire deployment and inflation process is about 0.04 seconds. Because vehicles change speed so quickly in a crash, airbags must inflate rapidly to reduce the risk of the occupant hitting the vehicle's interior.


Variable-force deployment

Advanced airbag technologies are being developed to tailor airbag deployment to the severity of the crash, the size, and posture of the vehicle occupant, belt usage, and how close that person is to the actual airbag. Many of these systems use multi-stage inflators that deploy less forcefully in stages in moderate crashes than in very severe crashes. Occupant sensing devices let the airbag control unit know if someone is occupying a seat adjacent to an airbag, the mass/weight of the person, whether a seat belt or child restraint is being used, and whether the person is forward in the seat and close to the airbag. Based on this information and crash severity information, the airbag is deployed at either a high force level, a less forceful level, or not at all. Adaptive airbag systems may utilize multi-stage airbags to adjust the pressure within the airbag. The greater the pressure within the airbag, the more force the airbag will exert on the occupants as they come in contact with it. These adjustments allow the system to deploy the airbag with a moderate force for most collisions; reserving the maximum force airbag only for the severest of collisions. Additional sensors to determine the location, weight or relative size of the occupants may also be used. Information regarding the occupants and the severity of the crash are used by the airbag control unit, to determine whether airbags should be suppressed or deployed, and if so, at various output levels.


Post-deployment

A chemical reaction produces a burst of nitrogen to inflate the bag. Once an airbag deploys, deflation begins immediately as the gas escapes through vent(s) in the fabric (or, as it is sometimes called, the cushion) and cools. Deployment is frequently accompanied by the release of dust-like particles, and gases in the vehicle's interior (called effluent). Most of this dust consists of
cornstarch Corn starch, maize starch, or cornflour (British English) is the starch derived from corn (maize) grain. The starch is obtained from the endosperm of the kernel. Corn starch is a common food ingredient, often used to thicken sauces or soups, ...
,
french chalk Talc, or talcum, is a clay mineral, composed of hydrated magnesium silicate with the chemical formula Mg3Si4O10(OH)2. Talc in powdered form, often combined with corn starch, is used as baby powder. This mineral is used as a thickening agent a ...
, or
talcum powder Talc, or talcum, is a clay mineral, composed of hydrated magnesium silicate with the chemical formula Mg3Si4O10(OH)2. Talc in powdered form, often combined with corn starch, is used as baby powder. This mineral is used as a thickening age ...
, which are used to lubricate the airbag during deployment. Newer designs produce effluent primarily consisting of harmless talcum powder/cornstarch and nitrogen gas. In older designs using an azide-based propellant (usually NaN3), varying amounts of
sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly caustic base and alkali ...
nearly always are initially present. In small amounts this chemical can cause minor irritation to the eyes and/or open wounds; however, with exposure to air, it quickly turns into
sodium bicarbonate Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...
(baking soda). However, this transformation is not 100% complete, and invariably leaves residual amounts of hydroxide ion from NaOH. Depending on the type of airbag system,
potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a salt ...
may also be present. For most people, the only effect the dust may produce is some minor irritation of the throat and eyes. Generally, minor irritations only occur when the occupant remains in the vehicle for many minutes with the windows closed and no ventilation. However, some people with
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
may develop a potentially lethal asthmatic attack from inhaling the dust. Because of the airbag exit flap design of the steering wheel boss and dashboard panel, these items are not designed to be recoverable if an airbag deploys, meaning that they have to be replaced if the vehicle has not been
written off A write-off is a reduction of the recognized value of something. In accounting, this is a recognition of the reduced or zero value of an asset. In income tax statements, this is a reduction of taxable income, as a recognition of certain expenses ...
in a collision. Moreover, the dust-like particles and gases can cause irreparable cosmetic damage to the dashboard and upholstery, meaning that minor collisions which result in the deployment of airbags can be costly, even if there are no injuries and there is only minor damage to the vehicle structure.


Regulatory specifications


United States

On 11 July 1984, the United States government amended
Federal Motor Vehicle Safety Standard 208 Federal Motor Vehicle Safety Standard 208 (FMVSS 208) regulates automotive occupant crash protection in the United States. Like all other Federal Motor Vehicle Safety Standards, FMVSS 208 is administered by the United States Department of Transpo ...
(FMVSS 208) to require cars produced after 1 April 1989 to be equipped with a passive restraint for the driver. An airbag or an
automatic seat belt A seat belt (also known as a safety belt, or spelled seatbelt) is a vehicle safety device designed to secure the driver or a passenger of a vehicle against harmful movement that may result during a collision or a sudden stop. A seat belt reduc ...
would meet the requirements of the standard. Airbag introduction was stimulated by the
National Highway Traffic Safety Administration The National Highway Traffic Safety Administration (NHTSA ) is an agency of the U.S. federal government, part of the Department of Transportation. It describes its mission as "Save lives, prevent injuries, reduce vehicle-related crashes" rela ...
. However, airbags were not mandatory on light trucks until 1997. In 1998, FMVSS 208 was amended to require dual front airbags, and reduced-power, second-generation airbags were also mandated. This was due to the injuries caused by first-generation airbags, though FMVSS 208 continues to require that bags be engineered and calibrated to be able to "save" the life of an ''unbelted'' 50th-percentile size and weight "male"
crash test dummy A crash test dummy, or simply dummy, is a full-scale anthropomorphic test device (ATD) that simulates the dimensions, weight proportions and articulation of the human body during a traffic collision. Dummies are used by researchers, automobi ...
. The technical performance and validation requirements for the inflator assembly used in airbag modules are specified in
SAE SAE or Sae may refer to: Science and technology : * Selective area epitaxy, local growth of epitaxial layer through a patterned dielectric mask deposited on a semiconductor substrate * Serious adverse event, in a clinical trial * Simultaneous Auth ...
USCAR 24–2.


Outside the United States

Some countries outside North America adhere to internationalized European ECE vehicle and equipment regulations rather than the United States Federal Motor Vehicle Safety Standards. ECE airbags are generally smaller and inflate less forcefully than United States airbags because the ECE specifications are based on ''belted'' crash test dummies. The
Euro NCAP The European New Car Assessment Programme (Euro NCAP) is a European voluntary car safety performance assessment programme (i.e. a New Car Assessment Program) based in Leuven (Belgium) formed in 1996, with the first results released in February ...
vehicle safety rating encourages manufacturers to take a comprehensive approach to occupant safety; a good rating can only be achieved by combining airbags with other safety features.Frontal impact test description
Euro NCAP website
Almost every new car sold in Europe is equipped with front and side airbags, but in the European Union in 2020 and in the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
, and most other developed countries there is no direct legal requirement for new cars to feature airbags. Ecuador requires dual front airbags in new car models since 2013. Since January 2014, with the exception of micro vehicles, all new cars made or imported in Argentina must have front airbags. Since 1 January 2014, all new cars sold in Brazil must have dual front airbags. Since July 2014, all new cars sold in Uruguay must have dual front airbags. Since December 2016, all new cars sold in Chile must have dual front airbags. Since 1 January 2017, all cars made or imported in Colombia must have dual front airbags. Since 1 January 2020, all new cars sold in Mexico must have dual front airbags. On 5 March 2021, the Indian
Ministry of Road Transport and Highways The Ministry of Road Transport and Highways (MoRTH) is a ministry of the Government of India, that is the apex body for formulation and administration of the rules, regulations and laws relating to road transport, transport research and in also ...
mandated that all new vehicle models introduced in India after 1 April 2021 have dual front airbags; the regulation also requires that all existing models be equipped with dual front airbags by 31 August 2021. India also mandated that all passenger vehicles sold after October 2023 must have a minimum of 6 airbags.


Maintenance

Inadvertent airbag deployment while the vehicle is being serviced can result in severe injury, and an improperly installed or defective airbag unit may not operate or perform as intended. Those servicing a vehicle, as well as first responders, must exercise extreme awareness, as many airbag control systems may remain powered for roughly 30 minutes after disconnecting the vehicle's battery. Some countries impose restrictions on the sale, transport, handling, and service of airbags and system components. In
Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
, airbags are regulated as harmful explosives; only
mechanics Mechanics (from Ancient Greek: μηχανική, ''mēkhanikḗ'', "of machines") is the area of mathematics and physics concerned with the relationships between force, matter, and motion among physical objects. Forces applied to objects r ...
with special training are allowed to service airbag systems. Some automakers (such as
Mercedes-Benz Mercedes-Benz (), commonly referred to as Mercedes and sometimes as Benz, is a German luxury and commercial vehicle automotive brand established in 1926. Mercedes-Benz AG (a Mercedes-Benz Group subsidiary established in 2019) is headquartere ...
) call for the replacement of undeployed airbags after a certain period of time to ensure their reliability in a collision. One example is the 1992 S500, which has an expiry date sticker attached to the door pillar. Some
Škoda Škoda means ''pity'' in the Czech and Slovak languages. It may also refer to: Czech brands and enterprises * Škoda Auto, automobile and previously bicycle manufacturer in Mladá Boleslav ** Škoda Motorsport, the division of Škoda Auto respons ...
vehicles indicate an expiry date of 14 years from the date of manufacture. In this case, replacement would be uneconomic as the car would have negligible value at 14 years old, far less than the cost of fitting new airbags.
Volvo The Volvo Group ( sv, Volvokoncernen; legally Aktiebolaget Volvo, shortened to AB Volvo, stylized as VOLVO) is a Swedish multinational manufacturing corporation headquartered in Gothenburg. While its core activity is the production, distributio ...
has stated that "airbags do not require replacement during the lifetime of the vehicle," though this cannot be taken as a guarantee on the device.


Limitations

Although the millions of installed airbags in use have an excellent safety record, some limitations on their ability to protect car occupants exist. The original implementation of front airbags did little to protect against
side collision A side collision is a vehicle crash where the side of one or more vehicles is impacted. These crashes typically occur at intersections, in parking lots, and when two vehicles pass on a multi-lane roadway. Occurrences and effects For fatali ...
s, which can be more dangerous than frontal collisions because the protective
crumple zone Crumple zones, crush zones, or crash zones are a structural safety feature used in vehicles, mainly in automobiles, to increase the time over which a change in velocity (and consequently momentum) occurs from the impact during a collision by a ...
in front of the passenger compartment is completely bypassed. Side airbags and protective airbag curtains are increasingly being required in modern vehicles to protect against this very common category of collisions. Airbags are designed to deploy once only, so are ineffective if any further collisions occur after an initial impact. Multiple impacts may occur during certain rollover or other incidents involving multiple collisions, such as many multivehicle collisions. An extremely dangerous situation occurs during "
underride collision A semi-trailer truck, also known as a semitruck, (or semi, eighteen-wheeler, big rig, tractor-trailer or, by synecdoche, a semitrailer) is the combination of a tractor unit and one or more semi-trailers to carry freight. A semi-trailer ...
s", in which a passenger vehicle collides with the rear of a
tractor-trailer A semi-trailer truck, also known as a semitruck, (or semi, eighteen-wheeler, big rig, tractor-trailer or, by synecdoche, a semitrailer) is the combination of a tractor unit and one or more semi-trailers to carry freight. A semi-trailer a ...
lacking a rear underride guard, or hits the side of such a trailer not equipped with a side underride guard. The platform bed of a typical trailer is roughly at the head height of a seated adult occupant of a typical passenger car. This means not much of a barrier exists between a head and the edge of the trailer platform, except a glass
windshield The windshield (North American English) or windscreen (Commonwealth English) of an aircraft, car, bus, motorbike, truck, train, boat or streetcar is the front window, which provides visibility while protecting occupants from the elements. Mo ...
. In an underride collision, the car's
crush zone Crumple zones, crush zones, or crash zones are a structural safety feature used in vehicles, mainly in automobiles, to increase the time over which a change in velocity (and consequently momentum) occurs from the impact during a collision by ...
s designed to absorb collision energy are completely bypassed, and the airbags may not deploy in time because the car does not decelerate appreciably until the windshield and roof pillars have already impacted the trailer bed. Even delayed inflation of airbags may be useless because of major intrusion into the passenger space, leaving occupants at high risk of major
head trauma A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inju ...
or
decapitation Decapitation or beheading is the total separation of the head from the body. Such an injury is invariably fatal to humans and most other animals, since it deprives the brain of oxygenated blood, while all other organs are deprived of the i ...
in even low-speed collisions. Western European standards for underride guards have been stricter than North American standards, which typically have allowed
grandfathering A grandfather clause, also known as grandfather policy, grandfathering, or grandfathered in, is a provision in which an old rule continues to apply to some existing situations while a new rule will apply to all future cases. Those exempt from t ...
of older equipment that may still be on the road for decades. Typical airbag systems are completely disabled by turning off the
ignition key A car key or an automobile key is a key used to open and/or start an automobile. Modern key designs are usually symmetrical, and some use grooves on both sides, rather than a cut edge, to actuate the lock. It has multiple uses for the automobile w ...
. Unexpected turnoffs usually also disable the engine,
power steering A power steering is a mechanical device equipped on a motor vehicle that helps drivers steer the vehicle by reducing steering effort needed to turn the steering wheel, making it easier for the vehicle to turn or maneuver at lower speeds. Hydraul ...
, and
power brakes Power brakes are a system of hydraulics used to slow down or stop most motor vehicles. It uses a combination of mechanical components to multiply the force applied to the brake pedal by the driver into enough force to actuate the brakes and stop ...
, and may be the direct cause of a collision. If a violent collision occurs, the disabled airbags will not deploy to protect vehicle occupants. In 2014, General Motors admitted to concealing information about fatal collisions caused by defective ignition switches that would abruptly shut down a car (including its airbags). Between 13 and 74 deaths have been directly attributed to this defect, depending on how the fatalities are classified.


Injuries and fatalities

Under some rare conditions, airbags can injure and in some very rare instances kill vehicle occupants. To provide crash protection for occupants not wearing seat belts, United States airbag designs trigger much more forcefully than airbags designed to the international ECE standards used in most other countries. Recent "smart" airbag controllers can recognize if a seatbelt is used, and alter the airbag cushion deployment parameters accordingly. In 1990, the first automotive fatality attributed to an airbag was reported. TRW produced the first gas-inflated airbag in 1994, with sensors and low inflation-force bags becoming common soon afterwards. Dual-depth (also known as dual-stage) airbags appeared on passenger cars in 1998. By 2005, deaths related to airbags had declined, with no adult deaths and two child deaths attributed to airbags that year. However, injuries remain fairly common in collisions with airbag deployment. Serious injuries are less common, but severe or fatal injuries can occur to vehicle occupants very near an airbag or in direct contact when it deploys. Such injuries may be sustained by unconscious drivers slumped over the steering wheel, unrestrained or improperly restrained occupants who slide forward in the seat during precrash braking, and properly belted drivers sitting very close to the steering wheel. A good reason for the driver not to cross hands over the steering wheel, a rule taught to most learner drivers, but quickly forgotten by most, is that an airbag deployment while negotiating a turn may result in the driver's hand(s) being driven forcefully into his or her face, exacerbating any injuries from the airbag alone. Improvements in sensing and gas-generator technology have allowed the development of third-generation airbag systems that can adjust their deployment parameters to the size, weight, position, and restraint status of the occupant. These improvements have demonstrated a reduced injury risk factor for small adults and children, who had an increased risk of injury with first-generation airbag systems. One model of airbags made by the
Takata Corporation was a Japanese automotive parts company. The company had production facilities on four continents, with its European headquarters located in Germany.Anghel, Alexandru (December 10, 2009)."Takata Petri hires 1,000 people in half a year in Arad and ...
used
ammonium nitrate Ammonium nitrate is a chemical compound with the chemical formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is ...
–based gas-generating compositions in airbag inflators instead of the more stable, but more expensive compound
tetrazole Tetrazoles are a class of synthetic organic heterocyclic compound, consisting of a 5-member ring of four nitrogen atoms and one carbon atom. The name tetrazole also refers to the parent compound with formula CH2N4, of which three isomers can be f ...
. The ammonium nitrate-based inflators have a flaw where old inflators with long-term exposure to hot and humid climate conditions could rupture during deployment, projecting metal shards through the airbag and into the driver. As of 2020, the defect has caused sixteen deaths and over 250 injuries in the U.S., and one death in Malaysia. The
National Highway Traffic Safety Administration The National Highway Traffic Safety Administration (NHTSA ) is an agency of the U.S. federal government, part of the Department of Transportation. It describes its mission as "Save lives, prevent injuries, reduce vehicle-related crashes" rela ...
(NHTSA) recalled over 33 million vehicles in May 2015, and fined Takata $70 million in November 2015. Toyota, Mazda, and Honda have said that they will not use ammonium-nitrate inflators.


Airbag fatality statistics

From 1990 to 2000, the United States NHTSA identified 175 fatalities caused by air bags. Most of these (104) have been children. About 3.3 million air-bag deployments have occurred during that interval, and the agency estimates more than 6,377 lives were saved and countless injuries were prevented.The statement "they've saved some 26,000 lives, according to estimates from the ... (NHTSA)" has been published. A rear-facing infant restraint put in the front seat of a vehicle places an infant's head close to the airbag, which can cause severe
head injuries A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inju ...
or death if the airbag deploys. Some modern cars include a switch to disable the front-passenger airbag, in case a child-supporting seat is used there (although not in Australia, where rear-facing child seats are prohibited in the front where an airbag is fitted). In vehicles with side airbags, it is dangerous for occupants to lean against the windows, doors, and pillars, or to place objects between themselves and the side of the vehicle. Articles hung from a vehicle's clothes hanger hooks can be hazardous if the vehicle's side-curtain airbags deploy. A seat-mounted airbag may also cause internal injury if the occupant leans against the door.


Aerospace and military applications

The
aerospace Aerospace is a term used to collectively refer to the atmosphere and outer space. Aerospace activity is very diverse, with a multitude of commercial, industrial and military applications. Aerospace engineering consists of aeronautics and astrona ...
industry and the
United States government The federal government of the United States (U.S. federal government or U.S. government) is the national government of the United States, a federal republic located primarily in North America, composed of 50 states, a city within a fede ...
have applied airbag technologies for many years.
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...
and
United States Department of Defense The United States Department of Defense (DoD, USDOD or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national secu ...
have incorporated airbag systems in various aircraft and spacecraft applications as early as the 1960s.


Spacecraft airbag landing systems

The first use of airbags for
landing Landing is the last part of a flight, where a flying animal, aircraft, or spacecraft returns to the ground. When the flying object returns to water, the process is called alighting, although it is commonly called "landing", "touchdown" or ...
were
Luna 9 Luna 9 (Луна-9), internal designation Ye-6 No.13, was an uncrewed space mission of the Soviet Union's Luna programme. On 3 February 1966, the Luna 9 spacecraft became the first spacecraft to achieve a survivable landing on a celestial bod ...
and
Luna 13 Luna 13 (E-6M series) was an unmanned space mission of the Luna program. Overview The Luna 13 spacecraft was launched toward the Moon from an Earth-orbiting platform and accomplished a soft landing on 24 December 1966, in the region of Oceanus P ...
, which landed on the Moon in 1966 and returned panoramic images. As with later missions, these would use the airbags to bounce along the surface, absorbing landing energy. The
Mars Pathfinder ''Mars Pathfinder'' (''MESUR Pathfinder'') is an American robotic spacecraft that landed a base station with a roving probe on Mars in 1997. It consisted of a lander, renamed the Carl Sagan Memorial Station, and a lightweight, wheeled robot ...
lander employed an innovative airbag landing system, supplemented with
aerobraking Aerobraking is a spaceflight maneuver that reduces the high point of an elliptical orbit (apoapsis) by flying the vehicle through the atmosphere at the low point of the orbit (periapsis). The resulting drag slows the spacecraft. Aerobraking is ...
,
parachute A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, who ...
, and
solid rocket A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine ...
landing thrusters. This prototype successfully tested the concept, and the two
Mars Exploration Rover Mission Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin atmosphe ...
landers employed similar landing systems. The
Beagle 2 The ''Beagle 2'' is an inoperative British Mars lander that was transported by the European Space Agency's 2003 ''Mars Express'' mission. It was intended to conduct an astrobiology mission that would have looked for evidence of past life on Mar ...
Mars lander also tried to use airbags for landing; the landing was successful, and the lander touched down safely, but several of the spacecraft's solar panels failed to deploy, thereby disabling the spacecraft.


Aircraft airbag landing systems

Airbags have also been used on military fixed-wing aircraft, such as the
escape crew capsule An escape crew capsule is an escape capsule that allows one or more occupants of an aircraft or spacecraft to escape from the craft while it is subjected to extreme conditions, such as high speed or altitude. The occupant remains encapsulated a ...
of the
F-111 Aardvark The General Dynamics F-111 Aardvark is a retired supersonic, medium-range, multirole combat aircraft. Production variants of the F-111 had roles that included ground attack (e.g. interdiction), strategic bombing (including nuclear weapons ca ...
.


Occupant protection

The
United States Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...
has incorporated airbags in its UH-60A/L Black Hawk and
OH-58D The Bell OH-58 Kiowa is a family of single-engine single-rotor military helicopters used for observation, utility, and direct fire support. It was produced by the American manufacturer Bell Helicopter and is closely related to the Model 206A ...
Kiowa Warrior helicopter fleets. The Cockpit Air Bag System (CABS) consists of forward and lateral airbags, and an inflatable tubular structure (on the OH-58D only) with an Electronic Crash Sensor Unit (ECSU). The CABS system was developed by the United States Army
Aviation Applied Technology Directorate The United States Army Aviation Applied Technology Directorate (AATD) is a tenant activity located at Fort Eustis, Virginia. It is a directorate of the Aviation Development Directorate under the Aviation and Missile Research, Development, and En ...
, through a contract with Simula Safety Systems (now
BAE Systems BAE Systems plc (BAE) is a British multinational arms, security, and aerospace company based in London, England. It is the largest defence contractor in Europe, and ranked the seventh-largest in the world based on applicable 2021 revenues. ...
). It is the first conventional airbag system for occupant injury prevention (worldwide) designed and developed and placed in service for an aircraft, and the first specifically for helicopter applications.


Motorcycle airbag systems

In the mid-1970s, the UK
Transport Research Laboratory TRL Limited, trading as TRL (formerly Transport Research Laboratory) is an independent private company offering a transport consultancy and research service to the public and private sector. Originally established in 1933 by the UK Government a ...
tested several types of
motorcycle airbag The air bag vest is a personal safety device worn by some motorcyclists and horse riders. Airbag vests initially found popularity among equestrian competitors, and airbags have become mandatory in professional motorcycle racing. In 2018, it became c ...
s. In 2006
Honda is a Japanese public multinational conglomerate manufacturer of automobiles, motorcycles, and power equipment, headquartered in Minato, Tokyo, Japan. Honda has been the world's largest motorcycle manufacturer since 1959, reaching a product ...
introduced the first production
motorcycle A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...
airbag safety system on its
Gold Wing The Honda Gold Wing is a series of touring motorcycles manufactured by Honda. Gold Wings feature shaft drive and a flat engine. Mooted by press in September 1974 as "The world's biggest motor cycle manufacturer's first attack on the over-750cc ...
motorcycle. Honda claims that sensors in the front forks can detect a severe frontal collision and decide when to deploy the airbag, absorbing some of the forward energy of the rider and reducing the velocity at which the rider may be thrown from the motorcycle. More commonly,
air bag vest The air bag vest is a personal safety device worn by some motorcyclists and horse riders. Airbag vests initially found popularity among equestrian competitors, and airbags have become mandatory in professional motorcycle racing. In 2018, it became c ...
s – either integrated into the motorcyclist's jacket or worn over it – have started to become used by regular riders on the street.
MotoGP Grand Prix motorcycle racing is the premier class of motorcycle road racing events held on road circuits sanctioned by the Fédération Internationale de Motocyclisme (FIM). Independent motorcycle racing events have been held since the start ...
has made it compulsory since 2018 for riders to wear suits with integrated airbags.


See also

*
Airbag dermatitis Airbag dermatitis (also known as an "airbag burn") is caused skin irritation and trauma secondary to the deployment of airbags. See also * Airbag * Contact dermatitis Contact dermatitis is a type of acute or chronic inflammation of the ski ...
*
Airplane airbags Airplane airbags are airbags that are located in the seat belts on some airplanes. They are designed to lessen the impact of crashes with minor injuries. Dependent on an airline's choice of installation, airplane airbags are most often install ...
*
Precrash system A collision avoidance system (CAS), also known as a pre-crash system, forward collision warning system, or collision mitigation system, is an advanced driver-assistance system designed to prevent or reduce the severity of a collision. In its ...
*
Safety standards Safety standards are standards designed to ensure the safety of products, activities and processes, etc. They may be advisory or compulsory and are normally laid down by an advisory or regulatory body that may be either voluntary or statutory. In ...


References


External links


Chemistry behind airbags

Pictures and details about the 1970s GM Air Cushion Restraint System
* History of air bags and how the technology gave rise to today's "smart cars". {{Authority control 1973 introductions 20th-century inventions Aircraft emergency systems American inventions Bags Vehicle parts Vehicle safety technologies