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Road Injury Prevention & Litigation Journal
Copyright © 1997 by TranSafety, Inc.
September 2, 1997
TranSafety, Inc.
(360) 683-6276
Fax: (360) 335-6402

Status of Injury and Crashworthiness Consumer Information
How Effective in Preventing Death and Injury Are Safety Belts and Air Bags?
Nissan Liable When Defective Restraint System Contributed to Severity of Plaintiff's Injuries
Compliance with Federal Standards Did Not Relieve Child Restraint Manufacturer from Liability under Common Law

Highway Safety Publications Catalog. Articles on Road Engineering, Road Maintenance & Management, and Injury Litigation. Information and consulting for the Automobile and Road User, as well as for law professionals in accident investigations.
TranSafety's free consumer journal for automobile and road users, three subscription journals on road maintenance, engineering, and injury litigation, and highway safety publications catalog. See our free consumer journal for automobile and road users, three subscription journals on road maintenance, engineering, and injury litigation, and a highway safety publications catalog.

How Effective in Preventing Death and Injury Are Safety Belts and Air Bags?

Motorists rely on "occupant protection systems" such as safety belts and air bags to save lives and prevent injuries in the event of a crash. Overall, American drivers and passengers have markedly increased their use of safety belts during the last ten years. As of December 1996, the national safety belt use rate was estimated at 68 percent. Since their introduction, air bags have been popular with motorists; and used in combination with safety belts, they provide "significant life-saving results." In 1995, more than 98 percent of all new cars sold were equipped with driver or dual (driver and passenger) air bag systems. From 1987 through September 1, 1995, more than 31 million cars with both driver and dual air bags had been registered. By September 1998, all new passenger cars and light trucks will require the installation of air bags and manual lap/shoulder belts.

In its third of five biennial reports to Congress, the National Highway Traffic Safety Administration (NHTSA) examined data on occupant protection systems. "Effectiveness of Occupant Protection Systems and Their Use" was published in December of 1996 and analyzed the fatality-and-injury-reducing effectiveness of air bags and safety belts in relation to different types of crashes and various driver-related issues. The report also examined safety concerns related to air bags and children.

To assess the fatality-reducing effectiveness of air bags, NHTSA's Fatal Accident Reporting System (FARS) was used. As of July 1996, FARS registered nearly 10,000 fatalities of front-seat occupants of cars and light trucks who were sitting in positions equipped with air bags. To analyze the injury-reducing effectiveness of both automatic and manual safety belts, researchers used NHTSA's National Accident Sampling System's (NASS) Crashworthiness Data System (CDS). It provides the most accurate and comprehensive measure of safety belt effectiveness. Unlike police accident reports, CDS does not rely solely on the crash victim's self-reporting of safety belt use.


Air bags were designed primarily to provide protection in frontal crashes, in which they "are now associated with a statistically significant fatality-reducing effectiveness of 34 percent." Commenting on the effectiveness of air bags in other types of crashes, the authors observed:

The life-saving benefits of air bags derive almost entirely from purely frontal crashes; . . . their benefit in partially frontal crashes, if any, is quite limited; and . . . the fatality reduction in all types of crashes is slightly more than one-third of the reduction in purely frontal crashes.

The estimated effectiveness of various occupant protection systems in reducing fatality risk for passenger car drivers in crashes of all types is as follows:

System Used Fatality Risk Reduction
Air bag plus lap-shoulder belt 50%
Air bag alone 13%
Manual lap-shoulder belt 45%

For vehicles involved in frontal collisions, air bags plus manual lap-shoulder belts provided the greatest protection against moderate injury, with an injury-reducing effectiveness of 61 percent. Exhibit 1 below graphs the estimated effectiveness of various types of occupant protection systems in reducing the chance of moderate injury. The figures represent the "percentage reduction in the chance of injury given that a crash has occurred, compared to an unrestrained occupant" at any position in the vehicle.

Estimated Effectiveness of Occupant Protection Systems in Reducing the Likelihood of Moderate Injury (MAIS 2+)

For serious-injury crashes, the table below shows the estimated effectiveness of occupant protection systems in reducing the likelihood of serious and greater injury by comparing the chance of injury to an unrestrained occupant to the chance of injury to a occupant using a specific type of restraint system.

System Used All Damage Areas Front Damage
Air bag plus lap-shoulder belt 59% 69%
Air bag alone 7% -8%
Automatic (2-point and 3-point) belt 37% 33%
Manual lap-shoulder belt 60% 74%

(Note: Bold denotes a statistically significant difference from the risk of unrestrained occupants.)

Exhibit 2 below is a graphical representation of the results of research on the effectiveness of occupant protection systems in reducing the chance of serious injury.

Estimated Effectiveness of Occupant Protection Systems in Reducing the Likelihood of Serious Injury (MAIS 3+)

The data showed that manual lap-shoulder belts, both with and without an air bag, provided significant protection against serious injury.


Occupant protection system effectiveness estimates were also developed for several driver-related issues, including body region of injury, gender, age, height, and weight. Patterns were revealed that may substantiate similar findings or suggest the need for further research and analysis.

Type of Injury Summarizing the relative risk of injury to different regions of the body, the authors noted:

The addition of an air bag to a lap-shoulder belt system appears to involve a beneficial trade-off: reductions in the more life-threatening moderate and serious injury to the head and chest, at the risk of increased likelihood of upper extremity injury. The air bag system alone (without the use of a safety belt) appears to be associated with increased risk of moderate injury to the chest, while providing less protection to the head and upper extremity than any of the three safety belt systems. This is further evidence of the need to always use safety belts, whether or not the vehicle is equipped with air bags. (Emphasis added.)

Gender The air bag plus lap-shoulder belt provided significant injury protection (64 percent) for male drivers, and manual lap-shoulder belts alone reduced the risk of injury by a significant 38 percent. For females, all safety belt systems provided significant injury reduction--59 percent for both the lap-shoulder belt alone and for the air bag plus lap-shoulder belt.

Age In general, drivers in the 15-49 age category reaped significant (62 percent) injury-reduction benefits from manual lap-shoulder belts alone and from these belts in tandem with air bags. Drivers age 50 and older experienced similar injury-reducing benefits (54-57 percent).

Height and Weight Researchers were puzzled by apparently contradictory and statistically insignificant results of height and weight analyses.


NHTSA has documented cases in which a deploying (inflating) passenger-side air bag seriously injured a child seated in that position. These critical-to-fatal head or neck injuries were sustained by infants in rear-facing child seats and by children facing forward in the right-front passenger seat. As a result of these findings, NHTSA issued a strong warning in a press release dated October 27, 1995. The warning urged care givers always to follow three "rules":

  • Make sure all infants and children are properly restrained in child safety seats or lap and shoulder belts for every trip.
  • The back seat is the safest place for children of any age.
  • Infants riding in rear-facing child safety seats should never be placed in the front seat of a vehicle with a passenger-side air bag.

Nearly all cases in which a deploying air bag injured drivers or passengers occurred because of the occupant's proximity to the air bag at the time of deployment. The most immediate remedy to child fatalities from deploying air bags is to ensure that all child passengers are properly belted and placed in the back seat. NHTSA uses press releases, media coverage, and other educational avenues to increase public awareness of the critical need to use all occupant protection systems properly.

On November 27, 1996, NHTSA issued a rule requiring vehicles with air bags to bear three new warning labels. The rule further required rear-facing child seats to display a new, improved warning label. Other immediate solutions to the problem of air-bag injuries have included using manual cut-off switches in vehicles lacking a rear seat to protect children and allowing dealers to deactivate air bags at an owner's request.

NHTSA believes smart air bags are the solution to a number of air bag problems, and they have been actively involved in efforts to produce them. NHTSA also solicits annual safety belt use data from each state and uses the data to continue promoting increased use of occupant protection systems at both the state and national level. With continued efforts, NHTSA believes the national safety belt use rate of 68 percent can be "increased significantly." Setting an example among public employees, NHTSA supports educational and promotional campaigns to increase safety belt use by federal, state, and local government employees and state and local police.

Copyright © 1997 by TranSafety, Inc.

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