Q&As: Airbags

May 2010

1 What are airbags?

Airbags are cushions built into a vehicle that protect occupants from hitting the vehicle interior or objects outside the vehicle (for example, other vehicles or trees) during a collision. The instant a crash begins, sensors start to measure impact severity. If the crash is severe enough (at or above the airbag deployment threshold), the sensors signal inflators to fill the bags with gas. The bags fill in a fraction of a second to cushion occupants. Occupant protection is maximized when safety belts are used in conjunction with airbags.

Video: frontal driver airbag deploying from the steering wheel

Frontal airbags: Most vehicles have airbags that deploy in frontal crashes to protect front-seat occupants. The frontal airbag for the driver is stowed in the steering wheel. The frontal airbag for the front passenger is stored in the instrument panel.

Some manufacturers provide knee airbags, mounted in the lower instrument panel. Knee airbags distribute impact forces to reduce leg injuries. They also help reduce forces on an occupant's chest and abdomen by controlling movement of the occupant's lower body.

Side airbags: Increasing numbers of vehicles also have airbags that deploy in side impact crashes. Side airbags are usually smaller than frontal airbags and deploy from the vehicle seatback, door, or roof to protect front- and sometimes rear-seat occupants.

Some side airbag systems protect only the torso (chest, abdomen, and pelvis) and some protect only the head. Those that protect both head and torso are optimal.

Head-protecting airbags may extend into the rear seating area. Rear seats may also have head-protecting side airbags separate from those in the front seat or airbags that provide torso protection.

Frontal dual airbag system	Side airbags to protect the head or head and torso
Side airbags to protect the head and torso

Video: full frontal test with and without airbag/safety belt, 95th percentile male dummy

2 Why do we need airbags?

Frontal airbags: In serious frontal crashes, the occupants inside the vehicle do not stop immediately, but continue moving forward. Frontal airbags are designed to work with lap/shoulder belts to protect the heads and chests of occupants from hitting the steering wheel, instrument panel, or windshield. If occupants strike these surfaces hard, they can sustain serious or fatal injuries.

Side airbags: In side impact crashes, the side structure of the struck vehicle or the structure of the striking vehicle can injure properly belted occupants. In some cases, occupants collide with nearby objects (like utility poles). Side airbags cushion and spread the load of these impacts to prevent any part of the body from sustaining concentrated impact forces. Side airbags that offer head protection are particularly important because they may be the only thing between an occupant's head and the front of a vehicle, a tree or other object, or the ground in the event of a rollover.

3 Are airbags required in all vehicles?

Frontal airbags: Since the 1999 model year, the federal government has required automakers to install driver and passenger airbags for frontal impact protection in all cars, light trucks, and vans. Most new vehicles had dual frontal airbags even before they were required safety equipment. Airbags grew in popularity starting in the early 1990s, and by the 1995 model year, virtually all cars and many light trucks had driver airbags. By the 1997 model year, most also had passenger airbags

Side airbags: Side airbags are not required by the government, but they are available on many vehicles. Ninety-one percent of all 2010 passenger vehicle models offer side airbags as either standard (88 percent) or optional (3 percent) equipment. Side airbags are provided as standard or optional equipment in all SUVs, 96 percent of cars, and 70 percent of pickups.

In September 2007, the National Highway Traffic Safety Administration (NHTSA) issued a side-impact safety standard that likely has resulted in more manufacturers voluntarily equipping their vehicles with side airbags. The standard requires automakers to provide increased head and torso protection for front seat and rear seat occupants in side-impact crashes but doesn't mandate side airbags specifically. In December 2009, NHTSA proposed a new safety standard intended to prevent occupant ejection through side windows during a crash, especially a rollover crash. The agency anticipated that automakers would meet the standard by modifying side airbags to make them larger to cover more of the window, stay inflated longer, and deploy during a side-impact or rollover crash.

Models with side airbag head protection systems

4 When do airbags deploy?

Airbags are designed to deploy only when they might be needed to prevent serious injury. In order for airbags to be effective they must deploy early in a crash; in a frontal crash this typically occurs within the first 50 milliseconds (0.05 seconds). A vehicle's airbag control module relies on feedback from crash sensors to predict whether an event is severe enough to warrant an airbag deployment.

Frontal airbags: Frontal airbags are designed to inflate in moderate to severe frontal crashes. Among airbags with advanced features that include a safety belt sensor, there are different inflation thresholds depending on whether people are using their safety belts. One threshold used by airbag designers is "must deploy" which includes a situation such as an impact into a rigid wall of 10-12 mph for unbelted occupants. The "must deploy" threshold is slightly higher — about 16 mph — for belted occupants because the belts alone are likely to provide adequate protection up to these moderate speeds. Frontal airbags may deploy to help protect occupants in side impacts if there is sufficient forward deceleration during the crash. For example, if a vehicle is moving forward at the time of a side impact, frontal airbags can help prevent serious injuries.

Advanced airbags compliant with government crash performance standards have been required in all passenger vehicles since model year 2007. Advanced airbags are designed to suppress deployment or alter deployment characteristics to reduce the risk of injury by the airbag if weight sensors in the seat detect that a front-seat passenger is small or in a child safety seat. Advanced airbags also can deploy at a lower energy level or pressure when passengers are small or out of position, or if the crash is of very low severity.

Side airbags: Because of the small space between an occupant and the side of the vehicle, side airbags must deploy very quickly to cushion occupants from intruding vehicles or objects. Some airbags typically deploy within the first 10-20 milliseconds of a side crash. "Must deploy" thresholds can be as low as 8 mph for narrow object crashes (e.g., trees and poles) and 18 mph for the more distributed side crashes (vehicle-to-vehicle crashes). Several auto manufacturers deploy the side airbags in frontal crashes to help control occupant movement during the rebound phase of a crash. Some curtain side airbags may stay inflated longer to protect occupants in rollover crashes. Allowing the airbags to remain inflated or triggering their deployment during a rollover can help prevent full or partial ejection of occupants.

Rollover airbags: Some types of side airbags also deploy in a rollover crash in response to sensors that measure a vehicle's sideways moving and tilting. Like curtain-style side airbags, these airbags deploy from the roof downward to cover side windows. Compared to curtain-style side airbags, rollover airbags typically are tauter, cover more of the side window to help prevent ejection, and stay inflated longer.

5 Is there a problem with nondeploying front airbags?

An article in The Kansas City Star in 2007 raised the possibility that nondeploying frontal airbags may be a major problem in fatal crashes.1 The article relied upon data from the Fatality Analysis Reporting System (FARS), a census of fatal crashes in the United States that primarily relies upon police reports.

An Institute study reviewed airbag deployment status for fatal frontal crashes contained in both FARS and the National Automotive Sampling System/Crashworthiness Data System, a sample of tow-away crashes with detailed data from crash investigators. Based on the more detailed crash data, failures of frontal airbags to deploy in fatal crashes were less frequent than suggested by FARS data, which had a substantial number of coding errors. Institute researchers estimated that 1-2 percent of frontal occupant deaths represented potential airbag system failures where deployments would have been expected. However, there are inherent uncertainties in judgments about whether or not airbags would be expected to deploy in some crashes.2

6 Are airbags effective? Do they save lives and reduce injuries?

Frontal airbags: NHTSA estimates that as of Jan. 1, 2009, more than 28,000 people are alive because of frontal airbags. Eighty-two percent were drivers and 18 percent were front-seat passengers. Forty percent were belted and 60 percent were unbelted.3

In frontal crashes, frontal airbags reduce driver fatalities by 29 percent and fatalities of right front passengers age 13 and older by 32 percent. The fatality reduction in frontal crashes is larger for unbelted drivers (34 percent), compared to belted drivers (21 percent). NHTSA estimates that the combination of an airbag plus a lap and shoulder belt reduces the risk of death by 61 percent, compared with a 50 percent reduction for belts alone in frontal crashes.4

Side airbags: Side airbags with head protection reduce a car driver's risk of death in driver-side crashes by 37 percent and an SUV driver's risk by 52 percent, an Institute analysis shows. Side airbags designed to protect only the torso reduce fatality risk by 26 percent for car drivers and by 30 percent for SUV drivers. Head-protecting side airbags reduce fatality risk for SUV drivers by 52 percent.5

7 Can airbags injure people?

Frontal airbags: Yes. Occasionally, the energy required to quickly inflate frontal airbags can cause injury. Fortunately, most of these injuries are minor scrapes and abrasions. Serious injuries and deaths are relatively rare.

In 1997, the federal government modified safety rules to encourage automakers to take energy out of airbags. Depowering began with 1998 models. Manufacturers were given the option to use sled tests with unbelted dummies to certify that their vehicles met crash performance rules. The maximum sled accelerations NHTSA prescribed under this option were lower than typically occur in crash tests so airbags didn't need to deploy as quickly or forcefully to catch and cushion unbelted dummies. Airbags meeting this standard are called sled-certified.

At the same time, a large-scale public education campaign encouraged parents to restrain children, especially infants in rear-facing restraints, in the back seat, where they're safest. Legislators in many states enacted laws requiring children to sit in the rear. Today most children ride restrained in back seats.6

The Institute examined the impact of depowering airbags and found an overall reduction in fatal crash risk associated with sled-certified, depowered airbags compared with earlier designs.7 A 2006 NHTSA study reported that redesigned airbags reduced fatality risk to child passengers by 45 percent as compared with pre-1998 airbags — without changing the beneficial effects for adults.8

The Blue Ribbon Panel for the Evaluation of Advanced Technology Airbag website

In 2001, NHTSA issued a certified-advanced airbag rule, with phase-in beginning with 2003 models. Anticipating the design changes that an advanced airbag standard would require, some automakers added new features ahead of the rule. Advanced airbags modify deployment patterns if weight sensors detect a small driver or front-seat passenger or a child safety seat. These airbags can be suppressed altogether or deploy with less force when passengers are small or out of position, or if a crash isn't severe. They also can determine if occupants' safety belts are buckled. Certified-advanced airbags generally deploy at lower thresholds for people who aren't using belts. The new rule changed the way auto manufacturers test vehicles for compliance. It introduced a range of crash tests using different-size dummies and different crash test speeds. Different tests still are performed for unbelted and belted dummies

According to a NHTSA investigation, another problem is that aftermarket equipment (e.g., laptop computer) mounted to the panel in front of the airbag deployment site can cause moderate or serious injury. If the airbag deploys, the aftermarket equipment may become a projectile or interfere with deployment. Consumers should check with their vehicle's manufacturer to find out the best place to safely install devices.9

Side airbags: Like frontal airbags, side airbags have the potential to cause injury. However, side airbags typically are smaller and deploy with less energy than frontal airbags.

8 How is the latest generation of advanced airbags performing?

A 2010 Institute study examined mortality rates in frontal crashes among front-seat occupants in vehicles with sled-certified airbags with and without advanced features and in vehicles with certified-advanced airbags. Mortality rates were 16 percent lower for drivers of vehicles with sled-certified airbags with advanced features; the benefit was 17 percent for adults riding in front passenger seats. Children benefited from both sled-certified airbags with advanced features and certified-advanced airbags, but adult drivers didn't. People who drove vehicles with certified-advanced airbags had a higher mortality rate than drivers of vehicles equipped with sled-certified airbags with advanced features. Belted drivers had the biggest increased risk of death — 21 percent. Mortality rates for right-front adult passengers and for unbelted drivers were similar for vehicles having certified-advanced airbags and sled-certified airbags with advanced features. The findings suggest potential problems with the way manufacturers are required to certify airbags as advanced. It may be that the new rule did not strike the right balance between protecting belted occupants and unbelted occupants.10

9 Who has been injured or killed by airbags?

Frontal airbags: NHTSA estimates that during 1990-2008, more than 290 deaths were attributable to frontal airbag inflation in low-speed crashes. Nearly 90 percent of the deaths occurred in vehicles manufactured before 1998, and approximately 68 percent were passengers. More than 90 percent of the passenger deaths were children and infants, most of whom were unbelted or in rear-facing child safety seats that placed their heads close to the deploying airbag.3 More than 80 percent of people killed were unbelted or improperly restrained. Unbelted occupants are likely to move forward if there is hard braking or other violent maneuvers before a frontal crash. These occupants can end up on top of, or extremely close to, the airbags as they begin to inflate. Short and elderly drivers can be vulnerable to inflation injuries from frontal airbags because they tend to sit close to the steering wheel.

Frontal airbags have changed considerably since the early 1990s, when the majority of airbag-related deaths occurred. The chief difference is a reduction in the energy (or power levels) with which airbags deploy. In addition, because of public education that children are safer in rear seats and state laws requiring children to sit in the rear, children increasingly are sitting in rear-seat positions. These and other changes have contributed to the drastic decline in frontal airbag-related deaths.

Side airbags: Three people were seriously injured by inflating side airbags during 1995-2008, according to NHTSA's Special Crash Investigations. One was an elderly male driver who suffered multiple rib fractures, and 2 were middle-age female drivers who suffered injuries to the spleen and ribs. NHTSA has identified only one child who has been injured by a side airbag — an unrestrained 3-year old sitting in the front seat who sustained minor facial skin lacerations from the side airbag cover. No children are known to have been seriously or fatally injured by a side airbag. A recent study of children in side crashes found no increased risk of injury to children age 15 and younger associated with side airbag deployment. This study did not assess the effects separately for head and torso airbags.11

10 What can be done to prevent injuries from frontal airbags?

Drivers: It is recommended that drivers sit with their chests at least 10 inches away from the center of the steering wheel. Many newer airbags take into account seating position and deploy with less force if an occupant is sitting close. However, for drivers of older vehicles who cannot get far enough away from the steering wheel, pedal extenders or an airbag on/off switch may be an option.

Only if it is not possible to get at least 10 inches from the steering wheel should an on/off switch be considered. Even if a safety belt is used, sitting this close to an airbag puts a driver's face at risk.

Infants and children: How and where infants and children are restrained in a vehicle can reduce the likelihood of an airbag-related injury. Infants, particularly those in rear-facing safety seats, should never sit in the front because this puts an infant's head too close to the frontal airbag. Rear seats are always safest for infants and children. Sixteen states have provisions requiring children of various ages to be seated in the rear. Even if your state's law does not require children to sit in the rear, children 12 and younger should always sit restrained in rear seats.

Seat belt and seating requirements by state

If an adult is transporting too many children for them all to sit safely and comfortably in the back seat(s), the youngest children should ride in the back. In this situation or when there is no back seat, and a child rides in the front seat, the seat should be as far back as possible and the child should be securely buckled in a lap/shoulder belt and sitting back in the seat. If a driver routinely has to put a child in the front seat, an airbag on/off switch may be considered.

Nearly all older children killed by frontal airbags were either unbelted or improperly belted. But even a belted child can be at risk by wiggling out of position or sitting on the edge of the seat, putting the head too close to the airbag. Proper belting and positioning are essential to safety.

11 What can prevent injuries from side airbags?

The risk of injury from a side airbag in the front and rear seats is extremely low for properly restrained and positioned adults or children. Children should not lean against the door area where the airbag is stored because the initial deployment force may be harmful. It is important for parents to understand that, with or without an airbag, children leaning against a door or lying down on a seat with their heads near the door or sides of a vehicle are at higher risk of injury in the event of a side impact.

The Side Airbag Out-of-Position Injury Technical Working Group (TWG) was formed because of concerns about potential injuries, particularly to small children who might lie down or assume other positions against a deploying side airbag. The TWG has a test protocol to assure that the inflation injury risk from deploying side airbags remains low. All vehicle manufacturers have committed to follow this protocol when designing new side airbag systems. According to NHTSA's online resource, safercar.gov, 94 percent of vehicles with side airbags conform to these voluntary guidelines.

NHTSA brochure: Buying a Safer Car

Rear-facing child restraints SHOULD NOT be used in the front seat with a passenger airbag. The forces of the inflating airbag against the back of the restraint can cause serious, even fatal, head injuries. Video: clip of this test

 

Pregnant women: Women in the late stages of pregnancy may not be able to get their abdomens far away enough from the steering wheel to be safe. There can be a risk of fetal injury from a frontal airbag if it inflates. However, without the airbag, there is a risk of fetal injury from hitting the steering wheel. Women in the late stages of pregnancy should avoid driving whenever possible. If they must drive, the combination of properly positioned safety belts and airbags offers the best protection.

12 Who needs an airbag on/off switch for frontal airbags?

The federal government has procedures allowing the very few people who may be at risk of serious airbag injury to get switches, but these aren't appropriate for most people. Installation of switches is permitted until Sept. 1, 2012. Most motorists can position themselves properly to avoid being too close to an inflating airbag. Airbags are designed to be used in conjunction with safety belts. Using a belt will reduce the chances of an occupant sliding too close to a deploying airbag.

Drivers: If a driver is unable to sit at least 10 inches away from the steering wheel, an airbag on/off switch could be considered. However, most 1998 and newer vehicles have redesigned airbags with less powerful inflators that reduce serious injury risk. Without an airbag, a driver's face is likely to hit the steering wheel in a frontal crash.

Passengers: Properly restrained adult passengers sitting back in the seat are not at significant risk from an inflating airbag. If a driver does get a switch, it should be used to turn off the airbag only in the rare case that an infant or child must ride in front.

Vehicles: Vehicles without rear seats are permitted to have an on/off switch installed for the passenger airbag. This includes some pickup trucks and some small cars.

13 Has the Institute crash-tested vehicles with side airbags?

Yes. In 2003 the Institute began a program of side impact crash tests for passenger vehicles. In the results so far, all of the good performers were equipped with side airbags that protect the head. But having side airbag protection for the head does not guarantee good performance. Vehicles also need side structures that resist major intrusion into the occupant compartment.

14 Is there new airbag technology coming?

Yes. Airbag technology is continuously developing. For example, Ford has developed an inflatable safety belt aimed at reducing rear-seat injuries. In a crash, the torso portion of the belt softly inflates, distributing crash forces across the torso and chest. Ford plans to make it available in some 2011 models. Toyota's iQ car has a rear window curtain airbag that deploys in front of the rear windshield and around the rear seat head restraints in the event of a rear crash. The car also has knee airbags for front-seat occupants. The iQ is available in Europe and Japan but not in the United States. Toyota also has developed an airbag that deploys from a center console in the rear seat during a side crash. The airbag would prevent rear passengers from colliding with each other. Toyota is launching these airbags in a new passenger vehicle model available in Japan.

Engineers have developed airbags that deploy on the outside of a vehicle to protect pedestrians, but they're not available yet. The idea is to protect a pedestrian's head with airbags that deploy from each windshield pillar.

15 Is it advisable to use airbags from salvaged vehicles to repair other vehicles?

No. Airbag modules recovered from salvaged vehicles should not be used to repair other vehicles. The designs of the airbag systems in most cars have been improved in recent years (sometimes improved several times). Therefore, matching a correct airbag module to a car that is being repaired is not straightforward.

Another issue involves the possibility of water damage. There is a risk that salvaged airbag modules will be from vehicles that have been in floods. Water damage can adversely affect airbag inflation characteristics. This problem may also arise if a salvaged airbag is directly exposed to water after being removed from a car. There is no standard method to test the functionality of salvaged airbags.

The widespread use of salvaged airbags for repairs is likely to exacerbate the already significant problem of airbag theft. Thieves have long targeted specific car parts such as radios and wheel covers, but in recent years they have developed a black market for airbags, which they sell at a low price to unethical repair-shop owners, who then charge customers the standard price for a replacement airbag.

16 Do motorcycles have airbags?

A frontal airbag is offered as an option on 2006 and later models of Honda's Gold Wing touring motorcycle. Honda's airbag is designed to deploy in severe frontal impacts and absorb some of the forward energy of the driver.

Honda Gold Wing touring motorcycle with frontal airbag

 

References

¹Casey, M. and Montgomery, R. 2007. Front airbags don't inflate in hundreds of head-on crashes. The Kansas City Star, October 22.

²Braver, E.R.; McCartt, A.T.; Sherwood, C.P.; Zuby, D.S.; Blanar, L.; Scerbo, M. 2010. Front air bag nondeployments in frontal crashes fatal to drivers or right-front passengers. Traffic Injury Prevention 11:178-87.

³National Highway Traffic Safety Administration. 2009. Special Crash Investigations — Counts of frontal air bag related fatalities and seriously injured persons. Washington, DC: US Department of Transportation.

⁴Kahane, C.J. 2004. Lives saved by the federal motor vehicle safety standards and other vehicle safety technologies, 1960-2002: passenger and light trucks. Report no. DOT HS-809-833. Washington, DC: National Highway Traffic Safety Administration.

⁵McCartt, A.T. and Kyrychenko S.Y. 2007. Efficacy of side airbags in reducing driver deaths in driver-side car and SUV collisions. Traffic Injury Prevention 8:162-70.

⁶National Highway Traffic Safety Administration. 2009. Child Restraint use in 2008 – overall results. Report no. DOT HS-811-135. Washington, DC: US Department of Transportation.

⁷Braver, E. R.; Kyrychenko, S.Y.; and Ferguson, S.A. 2005. Driver mortality in frontal crashes: comparison of newer and older airbag designs. Traffic Injury Prevention 6:24-30

⁸Kahane, C.J. 2006. An evaluation of the 1998-1999 redesign of frontal air bags. Report no. DOT HS-810-685. Washington, DC: National Highway Traffic Safety Administration.

⁹National Highway Traffic Safety Administration. 2009. Communications equipment and air bag interaction. Report no. DOT HS-811-089. Washington, DC: National Highway Traffic Safety Administration.

¹⁰Braver, E.R.; Shardell, M.; Teoh, E.R. 2010. How have changes in air bag designs affected frontal crash mortality? Annals of Epidemiology 20:499-510.

¹¹Arbogast, K.B. and Kallan, M.J. 2007. The exposure of children to deploying side airbags: an initial field assessment. Proceedings of the 51th Annual Conference of the Association for the Advancement of Automotive Medicine, 245-59. Barrington, IL: Association for the Advancement of Automotive Medicine.