Q&A: Airbags

September 2011

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, the sensors signal inflators to fill the bags with gas in a fraction of a second. Airbags offer the most protection when occupants are buckled up.

Video: frontal driver airbag deploying from the steering wheel

Frontal airbags: Most vehicles on the road today have airbags that deploy in frontal crashes to protect the heads and chests of front-seat occupants. The driver airbag is stowed in the steering wheel. The passenger airbag 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 and some protect only the head. Ideally, vehicles should have protection for both.

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

2 Why do we need airbags?

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

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

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 effective? Do they save lives and reduce injuries?

Frontal airbags: NHTSA estimates that as of Jan. 1, 2009, more than 28,000 people were alive because of frontal airbags, which became common in the 1990s and have been required in new passenger vehicles since the 1999 model year. Eighty-two percent of the people whose lives were saved by airbags were drivers and 18 percent were front-seat passengers. Forty percent were belted and 60 percent were unbelted.1

In frontal crashes, frontal airbags reduce driver fatalities by 29 percent and fatalities of front-seat passengers age 13 and older by 32 percent. The fatality reduction in frontal crashes is larger for unbelted drivers (34 percent), compared with 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.2

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.3

The crucial role played by head-protecting side airbags is illustrated by the results of the Institute's side impact crash tests, which measure how well passenger vehicles would protect occupants in a side crash. Since the program began in 2003, all the vehicles earning good ratings have been equipped with side airbags that protect the head. However, airbags alone aren't enough. Vehicles also need side structures that resist major intrusion into the occupant compartment.

4 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.

Side airbags: The government doesn't mandate side airbags specifically but does require a certain level of head and torso protection for all occupants in side impact crashes. The vast majority of new passenger vehicles come with side airbags as standard equipment.

Models with side airbag head protection systems

5 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; this typically occurs within the first 50 milliseconds (0.05 seconds) in a frontal crash and within the first 20 milliseconds (0.02 seconds) in a side crash. A vehicle's airbag control module relies on feedback from sensors to predict whether a crash is severe enough to warrant airbag deployment.

More information on when frontal, side, and rollover airbags deploy

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 safety belts. One threshold used by airbag designers is "must deploy," which includes a situation such as an impact into a rigid wall at 10-12 mph if occupants are unbelted. 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. 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.

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.

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 rollover, as well as side-impact, crashes.

6 Do frontal airbags ever fail to deploy when they're needed?

An Institute study reviewed airbag deployment status for fatal frontal crashes contained in the National Automotive Sampling System/Crashworthiness Data System, a sample of tow-away crashes with detailed data from crash investigators. 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 about whether or not airbags would be expected to deploy in some crashes.4

7 Can airbags injure people?

Occasionally, the energy required to quickly inflate airbags can cause injury. This used to be a serious concern with frontal airbags, but, thanks to new government requirements, airbag injuries are becoming a thing of the past. Fortunately, even with older airbags, most of the injuries that occur are minor scrapes and abrasions, and serious injuries and deaths are relatively rare.

NHTSA estimates that during 1990-2008, more than 290 deaths were caused by 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. More than 80 percent of people killed were unbelted or improperly restrained.1

Unbelted occupants are likely to move forward if, for example, there is hard braking or swerving 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.

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

Three people were seriously injured by inflating side airbags during 1995-2008, according to NHTSA's Special Crash Investigations. No children are known to have been seriously or fatally injured by a side airbag.

A recent field 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.5

8 What can drivers do to prevent injuries to themselves and their passengers from frontal airbags?

Drivers: Drivers should 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. 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. The government is allowing installation of switches until Sept. 1, 2012.

Information about obtaining an on/off switch

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.

Infants and children: How and where infants and children are restrained in a vehicle are critical factors in avoiding airbag-related injuries. 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. Seventeen 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, the youngest children should ride in the back. When a child does need to ride 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 against the seatback. If a driver routinely has to put a child in the front seat of an older vehicle, an airbag on/off switch may be considered.

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

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: Rear-facing infant seat with deploying airbag

9 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 seated and restrained adults or children. Children should not lean against the door area where the airbag is stored because the initial deployment force may be harmful. With or without an airbag, children who lean against doors or lie down with their heads near the doors or sides of vehicles are at higher risk of injury in the event of a side impact.

All vehicle manufacturers have committed to follow a test protocol for designing new side airbag systems that assures that the inflation injury risk is low even for small children who might lie down or assume other positions against a deploying side airbag. According to NHTSA's online resource, safercar.gov, 94 percent of vehicles with side airbags conform to these voluntary guidelines.

10 What steps has the government taken to minimize the risk of injury from airbags?

In 1997, the federal government modified safety rules to encourage automakers to take energy out of frontal airbags. Depowering began with 1998 models. Manufacturers were allowed 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

Institute researchers 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

In 2001, NHTSA issued a certified-advanced airbag rule that required more sophisticated airbags in all passenger vehicles by the 2007 model year. 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 and 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.

11 How is the latest generation of advanced airbags performing?

Airbags continue to save lives, but the newest ones aren't working as well as the ones they replaced.

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 compared with sled-certified airbags without advanced features; the benefit was 17 percent for adults riding in front passenger seats.

Results for the newest airbags – certified-advanced – didn't follow the same pattern. 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 didn't strike the right balance in protecting belted and unbelted occupants.9

12 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 offer it as an option on the 2011 Explorer. Toyota's iQ microcar 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 iQ is available in Europe and Japan and is scheduled to go on sale in the US in early 2011 as the Scion iQ. 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 this airbag in a new 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.

13 Is it OK to use airbags from salvaged vehicles to repair other vehicles?

A new replacement airbag module from the original manufacturer of the vehicle should be used for vehicles that require an airbag replacement. However, when the option to purchase a new airbag module is not possible, the Institute recommends that care be taken to identify a salvaged airbag module that has been inspected and certified. Certification documentation should include the vehicle identification number of the vehicle from which the airbag was removed, the airbag salvage date, storage location, and shipment details. Buyers should check if recalls apply to the airbag by checking the NHTSA recall database.

14 What are the risks associated with using salvaged airbag modules to repair other vehicles?

Processing salvaged airbag modules can present a number of difficulties.

The designs of the airbag systems in most cars have been improved in recent years (sometimes several times). Therefore, there's a significant possibility of a mismatch between the salvaged airbag module and the vehicle being repaired.

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, or that the airbag module was exposed to precipitation while at the salvage facility. Water damage can adversely affect the way an airbag inflates. 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.

Using salvaged airbags could also encourage airbag theft, which is already a significant problem. In recent years thieves 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.

15 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. No studies have been conducted into the real-world effectiveness of motorcycle airbags.

Honda Gold Wing touring motorcycle with frontal airbag

 

References

¹National 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.

²Kahane, 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.

³McCartt, 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.

⁴Braver, 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.

⁵Arbogast, 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.

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.

⁹Braver, 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.