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DOT HS 808 470 August 1996

NHTSA Technical Report

Fatality Reduction by Air Bags

Analyses of Accident Data through Early 1996

This document is available to the public from the National Technical Information Service, Springfield, Virginia 22161.
This publication is distributed by the U.S. Department of

Transportation, National Highway Traffic Safety Administration, in the interest of information exchange. The opinions,

findings and conclusions expressed in this publication are those

of the author(s) and not necessarily those of the Department

of Transportation or the National Highway Traffic Safety

Administration. The United States Government assumes no

liability for its contents or use thereof. If trade or manufacturers' name or products are mentioned, it is because they are

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Technical Report Documentation Page

1 - Report No.

DOT HS 808 470

2. Govemmenr Accession No. 3. Recipient's Catalog No.

4. Title and Subtitle

FATALITY REDUCTION BY AIR BAGS

ANALYSES OF ACCIDENT DATA THROUGH EARLY 1996

7. Author' s)

Charles J. Kahane, Ph.D.

5. Report Data

August 1996

6. Performing Organization Code

8. Performing Organization Report Nc

9. Performing Organization Name and Address 10. Work Unit No. !TRAIS)

Evaluation Division, Plans and Policy

National Highway Traffic Safety Administration

Washington, D.C. 20590

11. Conrroct or Gran' No.

12. Sponsoring Agency Nome and Address

Department of Transportation

National Highway Traffic Safety Administration

Washington, DC. 20590

13. Type of Report ond PenoO Covered

NHTSA Technical Report

Sponsoring Agency Cade

15. Supplementary. Notes

1 6. Abstract

The fatality risk of front-seat occupants of passenger cars and light trucks equipped with air

bags is compared to the corresponding risk in similar vehicles without air bags, based on statistical analyses

of Fatal Accident Reporting System (FARS) data from 1986 through early 1996. The principal conclusion

is that driver air bags save lives. The fatality reduction benefit of air bags for all drivers is an estimated 11

percent; this percentage is essentially unchanged from 1992 and 1994 analyses by NHTSA staff. New,

positive findings are that driver air bags save lives in light trucks and in small cars, that passenger air bags

save lives of right-front passengers age 13 or older, and that driver air bags provide a significant

supplemental life-saving benefit for the driver who buckles up (as well as saving lives of unbelted drivers).

On the other hand, preliminary analyses of limited accident data show a higher fatality risk for child

passengers age 0-12 in cars with current dual air bags than in cars without a passenger air bag. Also,

current air bags may have diminished, or even negligible benefits for drivers age 70 or older, and they do

not have a statistically significant effect for drivers of any age group in oblique-frontal crashes.

17. Kay Words

air bag; occupant protection; fatal crash;

crashworthiness; FARS; fatality reduction;

accident analysis; statistical analysis;

evaluation; frontal impact; frontal crash;

18. Distribution Statement

Document is available to the public through

the National Technical Information Service,

Springfield, Virginia 22161

1 9 . Securit y Clolsif . (of thi s report )

Unclassified

20. Security Closuf. (of this poge)

Unclassified

21. No. of Pogei

142

22. Pnce

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

TABLE OF CONTENTS

Executive summary v

1. Overall fatality reduction for air bags 1

1.1 Overview of the automatic protection requirement 1

1.2 Fatalities, as of early 1996, at seating positions equipped with air bags 2

1.3 FARS data preparation 4

1.4 Definitions of "fatality reduction" 6

1.5 Fatality reduction for driver air bags - passenger cars 7

1.6 Fatality reduction for driver air bags - light trucks 12

1.7 Fatality reduction for passenger air bags - car passengers age 13 or older 14

1.8 Estimated increase of fatalities, through 1995, if there had been no air bags ... . 19

1.9 Summary of fatality reduction estimates 19

2. Fatality reduction by type of crash, vehicle or occupant 23

2.1 By impact location 23

2.2 By car weight 33

2.3 By vehicle manufacturer 35

2.4 Single vs. multivehicle crashes 36

2.5 By occupant age and sex 38

2.6 Passenger air bags and children 44

3. Air bag effectiveness for belted vs. unrestrained car drivers 51

3.1 What does it matter? 51

3.2 Estimates based on FARS-reported belt use 52

3.3 Analyses that do not rely on FARS belt use reporting 63

3.4 Summary 70

References 73

Appendix A Passenger cars: types of occupant protection by make-model and year 77

Appendix B Light trucks: types of occupant protection by make-model and year 97

Appendix C Supplementary tables: detailed analyses of fatality reduction 103

Appendix D Belt use observed in State surveys, 1990-94 139

EXECUTIVE SUMMARY

Driver air bags first appeared as standard equipment on a few 1985 make-models. When automatic

occupant protection was phased into passenger cars during model years 1987-90, the National

Highway Traffic Safety Administration (NHTS A) did not mandate air bags, but allowed any system

meeting the agency's test requirements, such as air bags or automatic belts. Nevertheless, the agency

explained that the combination of a 3-point safety belt, correctly buckled, plus an air bag provides the

best occupant protection. The public agreed, expressing an almost immediate preference for air bags

over automatic belts. In 1990, more than a million cars with driver air bags were sold. By 1993, the

majority of new cars had driver air bags, and by 1994, dual air bags. By 1995, the majority of new

light trucks had driver or dual air bags. All new cars will be required to have dual air bags and

manual 3-point belts in model year 1998, and all new light trucks in 1999.

Pursuant to Executive Order 12286, NHTSA evaluates the actual safety benefits of its existing

regulations, based on statistical analyses of accident data, to see if the standards are indeed effective

and meeting their regulatory goals. The fatality-reducing effectiveness of air bags is a matter of

continuing interest to NHTSA. Statistical analyses of the available accident data were published in

1992 and 1994. The 1992 analysis found that air bags for drivers of passenger cars were reducing

fatality risk by 11 percent; the 1994 analysis found a 10 percent reduction. NHTSA now has records

of 7933 driver fatalities in cars equipped with air bags, as compared to 777 at the time of the 1992

study and 2069 in 1994. A more detailed analysis of fatality reduction can be performed for car

drivers. Also, since there have been 855 driver fatalities in light trucks and vans equipped with air

bags and 782 right-front passenger fatalities in cars equipped with dual air bags, it is possible to take

a first look at the effect of air bags for drivers of light trucks and for car passengers.

Analyses are based on Fatal Accident Reporting System (FARS) data from 1986 to early 1996.

FARS is a census of fatal crashes in the United States. Two statistical methods are used to assess

fatality reduction. The first hinges on the fact that millions of cars and light trucks have an air bag

for the driver, but not the right-front passenger; the ratio of driver to passenger fatalities in these

vehicles is compared to corresponding ratios in similar vehicles with air bags at neither position, or

at both. The second method hinges on the fact that air bags are primarily designed to deploy and

have potential benefits in frontal crashes; the ratio of frontal to nonfrontal fatalities in vehicles

equipped with air bags is compared to the corresponding ratio in similar vehicles without air bags.

Results by the two methods are averaged. Fatality reductions are described as "statistically

significant" if one or (in most cases) both methods show a significant reduction. The report describes

how statistical significance is tested and how confidence bounds are calculated.

The primary objective is to find the overall, average fatality reduction by air bags for the entire

population of occupants, including those who use their safety belts and those who do not. However,

to the extent that the data allow, it is also important to estimate separately the effect of an air bag for

an unbelted occupant, and the supplemental fatality reduction by air bags for an occupant who wears

safety belts.
The principal conclusion of the study is that driver air bags save lives. The fatality reduction benefit

of air bags for all drivers is an estimated 11 percent; this percentage is essentially unchanged from the

1992 and 1994 analyses. New, positive findings are that driver air bags save lives in light trucks and

in small cars, that passenger air bags save lives of right-front passengers age 13 or older, and that

driver air bags provide a significant supplemental life-saving benefit for the driver who buckles up (as

well as saving lives of unbelted drivers).

On the other hand, in-depth crash investigations have revealed 22 cases, as of July 1996, where

children may have sustained fatal lesions from interactions with passenger air bags. The accident data

now in the FARS are insufficient to determine a specific numerical value for the effect of air bags for

child passengers. However, to the extent that preliminary analyses show a higher fatality risk for child

passengers age 0-12 in cars with dual air bags than in cars without a passenger air bag, the current

data sustain the concerns raised by the in-depth investigations. Statistical analyses also suggest two

other possible problems with current air bags: they may have diminished, or even negligible benefits

for drivers age 70 or older, and they do not have a statistically significant effect for drivers of any age

group in oblique-frontal crashes.

The main findings and conclusions of the evaluation are the following:

AIR BAGS SAVE LIVES

• If no passenger cars or light trucks had been equipped with driver or passenger air bags, it is

estimated that a total of 1136 additional fatalities would have occurred during 1986-95

(approximate confidence bounds: 692 to 1622).

OVERALL FATALITY REDUCTION - DRIVER AIR BAGS - PASSENGER CARS

• Air bags reduce the overall fatality risk of car drivers by a statistically significant 11 percent

(confidence bounds: 7 to 15 percent). In other words, a fleet of cars equipped with air bags

will have 11 percent fewer driver fatalities, total, than the same cars would have had if they

did not have air bags.

• Driver air bag effectiveness is holding steady. The estimate of fatality reduction is essentially

unchanged from the 1992 and 1994 analyses by NHTSA staff.

PURE FRONTALS VS. PARTIAL FRONTALS - DRIVER ATR BAGS - PASSENGER CARS

• Driver air bags for passenger cars are effective in purely frontal impacts (12:00 damage and

no subsequent rollover). The estimated fatality reduction is a statistically significant 3014

percent (confidence bounds: 24 to 37 percent).
Air bags are significantly less effective for car drivers in partially frontal impacts (11, 1, 10

or 2:00 damage; or 12:00 damage with subsequent rollover) than in purely frontal impacts.

FATALITY REDUCTION - DRIVER AIR BAGS - LIGHT TRUCKS AND VANS

• Driver air bags in light trucks - pickup trucks, vans and sport utility vehicles - are effective

in purely frontal crashes. The fatality reduction is a statistically significant 27 percent

(confidence bounds: 14 to 40 percent).

• Air bags reduce the overall fatality risk of light truck drivers by a statistically significant 10

percent.

• The preliminary conclusion is that driver air bags are about as effective in light trucks and

vans as they are in cars. However, many of the vehicles that first got air bags were minivans.

The conclusion will need to be reassessed as more data become available, especially for

pickup trucks and sport utility vehicles.

FATALITY REDUCTION - PASSENGER AIR BAGS - CAR PASSENGERS AGE 13 OR OLDER

• Passenger air bags in cars are effective for right-front occupants age 13 or older in purely

frontal crashes. The fatality reduction is a statistically significant 27 percent (confidence

bounds: 9 to 45 percent).

• Air bags reduce the overall fatality risk of car passengers age 13 or older by a statistically

significant 13V4 percent.

• The preliminary conclusion is that air bags are about as effective for passengers age 13 or

older as for drivers. If so, it is estimated that an additional 88 right front passengers age 13

or older would have died during 1986-95 if no passenger cars or light trucks had been

equipped with passenger air bags.

PASSENGER AIR BAGS AND CHILDREN AGE 0-12

• The agency's Special Crash Investigation teams, as of July 1996, have identified 22 fatalities

of child passengers in low-severity frontal crashes of vehicles equipped with dual air bags (14

before the end of 1995 and 8 during January-July 1996). Infants in rear-facing safety seats,

and unrestrained or improperly restrained children who were out of position prior to the main

impact, appear to have contacted the air bag during the forceful early phase of its deployment.

v n
• Preliminary analyses of the limited available accident data show increases in fatality risk with

passenger air bags for right-front passengers age 0-12 in frontal crashes. The observed effects

vary widely, depending on the analysis method, and they are only statistically significant in

some of the analyses. In other words, although a specific numerical value on the effect of air

bags cannot yet be determined, the results are consistent with the conclusion, from special

crash investigations, that child passengers are experiencing problems with air bags.

• The Department of Transportation has formed a coalition with manufacturers, insurance

companies and other organizations to prevent injuries and fatalities which may be

inadvertently caused by air bags, especially to children. The May 21, 1996 press release

announcing the coalition offers the following safety guidelines for child passengers:

"Infants in rear-facing child safety seats should never be placed in the

front seat if the vehicle has a passenger-side air bag. The safest place for

children of all ages is the back seat. If riding in the back seat is not an

option, toddlers and older children may ride in the front seat of a vehicle

with a passenger-side air bag, but only if buckled up properly and with

the seat moved as far back as possible."

• On August 1, 1996, NHTSA proposed changes to the air bag requirement with a goal of

reducing the risks of air bags to children:

The motor vehicle industry is encouraged to begin installing, at the earliest possible

date, a 'smart' passenger air bag system that will detect when a child is present and

automatically deactivate the air bag or enable it to deploy safely.

One kind of 'smart' system that appears to be available now is a weight sensor in the

seat that prevents the air bag from deploying when a child is in the seat.

Manufacturers who do not provide a qualifying 'smart' system would be required to

have new and more prominent air bag warning labels inside the vehicle. They would

also be permitted to install cutoff switches so parents can deactivate the passengerside air bag when a child is seated in front of it.

The press release announcing these proposals emphasized that parents can generally

eliminate the air bag risk immediately by insisting that their children ride

buckled up in the rear seat.

• During 1986-95, as stated above, 14 child passengers apparently received fatal injuries from

interactions with passenger air bags in low-severity frontal crashes. During that time, it is

estimated that passenger air bags saved the lives of 88 passengers age 13 or older.

vm
OLDER DRIVERS AND AIR BAGS

• The data lead to a preliminary conclusion that air bags are less effective for the driver age 70

or older than for the young or middle-aged driver.

AIR BAG EFFECTIVENESS FOR UNBELTED VS. BELTED CAR DRIVERS

• For drivers reported as unbelted in FARS, air bags reduced fatality risk by a statistically

significant 34 percent in purely frontal impacts (confidence bounds. 25 to 42 percent).

• For drivers reported as belted in FARS, air bags reduced fatality risk by a statistically

significant 21 percent in purely frontal impacts (confidence bounds: 9 to 33 percent). In other

words, in a purely frontal impact, a belted driver has 21 percent lower fatality risk in a car

equipped with an air bag than in a similar car without an air bag.

• In States with low belt use, the overall fatality reduction for driver air bags was statistically

significant in purely frontal crashes. In States with high belt use, the reduction was also

significant, but not quite as large as in the States with low belt use.

• Based on the preceding analyses, it is concluded that air bags save lives for unbelted drivers,

and that they save lives for belted drivers.

• It is also concluded that air bags are probably somewhat more effective, in relative terms, for

the unbelted driver than for the belted driver.

• The overall fatality reduction by air bags for unbelted drivers in all crashes (not just purely

frontal impacts) is estimated to be 13 percent (confidence bounds: 6 to 19 percent).

• The supplemental fatality reduction by air bags for belted drivers in all crashes is estimated

to be 9 percent (confidence bounds: 3 to 15 percent).

SMALL VS. LARGE CARS

• The observed overall fatality reduction by air bags is about the same in light-weight, mediumweight and heavy cars. It is concluded that air bags are effective in small cars, and quite

possibly no less effective, in relative terms, than in large cars.

I X
CHAPTER 1

OVERALL FATALITY REDUCTION FOR AIR BAGS

1.1 Overview of the automatic protection requirement

Federal Motor Vehicle Safety Standard 208 ("Occupant Crash Protection"), as amended on July 17,

1984, required that automatic occupant protection, such as air bags or automatic belts, be phased into

passenger cars during 1987-90 [2], Part 571.208; [10]. When the National Highway Traffic Safety

Administration (NHTSA) issued FMVSS 208, it also began a continuing, nationwide effort to

increase belt use through encouragement of State buckle-up laws, enforcement and public education.

Use of manual lap and shoulder belts reduces the risk of fatal injury to front-seat occupants by 45

percent, but in 1983, only 14 percent of the general driver population buckled up [13], pp. IV-11 -

IV-16; [26]. Initially, automatic belts installed in response to FMVSS 208 helped increase belt use.

In the long run, however, NHTSA believed that the best protection would come from air bags in

combination with buckle-up laws in most of the States to ensure high rates of belt use.

The actual course of events after 1984 was even better than what the agency had hoped for. Public

consciousness of health and safety issues generally, and road safety in particular, increased during

the 1980's. The FMVSS 208 regulation broke the logjam on belt laws. Many States passed buckleup laws, and belt use tripled between 1984 and 1987 [6], p. 12. By 1995, all of the States plus the

District of Columbia and Puerto Rico had enacted them. The public expressed an almost immediate

preference for air bags over automatic belts, and the manufacturers moved quickly to meet the

demand for air bags. By the early 1990's it was clear that the United States was heading for an all-air

bag fleet and nearly universal belt laws that have a high level of public support. Automatic belts have

become essentially irrelevant, since belt laws have greatly increased use of manual belts. As of model

year 1995, automatic belts have been largely phased out of cars and light trucks. Two past

evaluations of fatality reduction consistently showed that most types of automatic belts have about

the same net effect as manual belts; one type (motorized belts without disconnect) perhaps offers a

slight additional benefit over manual belts, because the use rate of the shoulder belt is very high,

although the use of the manual lap belt is low [6], [19]. Since the effectiveness estimates in those

studies were based on large samples of accident data, no further evaluation of automatic belt

effectiveness is performed in this report.

Air bags evolved first for drivers and only later for right-front passengers. To encourage the early

installation of air bags, even if only for drivers, FMVSS 208 excluded the right-front passenger

position from the automatic protection requirement in cars with driver air bags produced before

September 1,1993. Since model year 1994, automatic protection (but not necessarily air bags) has

been required at both positions in all new cars. This feature of FMVSS 208 has resulted in a large

fleet of cars with an air bag and manual belts for the driver, and manual belts only for the right-front

passenger. This feature, and the strong consumer demand for air bags have also resulted in a wide

variety of combinations of belts and bags in cars. Up to model year 1991, with few exceptions, only

six types of automatic protection were installed in cars:
(1) Driver air bag plus manual 3-point belts for the driver and the right-front passenger

(2) Driver and right-front passenger air bags with manual 3-point belts

(3) Motorized 2-point belts without disconnect, plus manual lap belts

(4) Motorized 2 point belts with disconnect, plus manual lap belts

(5) Nonmotorized, door-mounted 3-point belts

(6) Nonmotorized, door-mounted 2 point belts, usually with manual lap belts

In 1992-93, however, combinations of an air bag(s) and automatic belts became fairly common as

manufacturers endeavored to install air bags as soon as possible but left unchanged the automatic belt

systems that were already installed in that make-model in a previous year. In 1994, when all cars had

to have automatic protection at both positions, but not all cars were ready for dual air bags, about

30 percent of the fleet had an air bag for the driver and an automatic belt at the right-front seat only,

or at both positions.

In 1991, NHTSA extended the automatic occupant protection requirements to light trucks - pickup

trucks, vans and sport utility vehicles (SUV) - to be phased in during model years 1995-98 [2],

Manufacturers are almost always using air bags, not automatic belts, to meet the requirement. They

also installed a large number of driver-only air bags, in advance of the FMVSS.

In accordance with the Intermodal Surface Transportation Efficiency Act of 1991, FMVSS 208 was

again amended to require all passenger cars manufactured after September 1, 1997 and all light trucks

manufactured after September 1, 1998 to have dual air bags, plus lap and shoulder belts [2].

Automatic belts, and the combinations of air bags with automatic belts, will be phased out. Already,

in model year 1995, the overwhelming majority of new cars have dual air bags and manual belts.

1.2 Fatalities, as of early 1996, at seating positions equipped with air bags

NHTSA periodically evaluates the effectiveness of the occupant protection program in accordance

with a plan published in 1990 [11] and in response to Executive Order 12866 [12] and the Intermodal

Surface Transportation Efficiency Act of 1991. Agency staff have published two analyses of fatality

reduction by air bags. The agency's June 1992 Interim Report on the Evaluation of the Effectiveness

of Occupant Protection was based on Fatal Accident Reporting System (FARS) data through mid1991 [6]. At that time there were records of 790 occupant fatalities in passenger cars at seating

positions equipped with air bags: 777 drivers and 13 right-front passengers. There were enough data

to show a statistically significant reduction of driver fatalities in frontal crashes, and to support a

conclusion that driver air bags save lives in passenger cars. They were not enough data for analyses

of subgroups of drivers, vehicles or crashes. Fatality Reduction by Automatic Occupant Protection

in the United States, Kahane's 1994 paper at the conference on the Enhancement of Safety in

Vehicles (ESV), was based on FARS data through mid-1993, including records of 2107 occupant

fatalities in passenger cars at seating positions equipped with air bags (2069 drivers and 38 right-front

passengers) [19]. That is almost three times as many fatal cases as in the Interim Report, enough to

show statistically significant fatality reductions for driver air bags by several analysis methods, and

to reveal that air bags were quite effective in straight-ahead (12:00) frontal impacts, but not in oblique

frontal impacts.
The current analysis includes FARS data through early 1996. There are 9609 records of fatalities at

seating positions equipped with air bags, more than four times the data in the ESV paper. They

include 7933 car drivers, enough for fairly detailed analyses of fatality reduction by vehicle size,

occupant age, etc. They also include 782 car passengers and 855 light-truck drivers: large enough

numbers for initial analyses of overall fatality reduction with good prospects of obtaining statistically

significant results (i.e., about the same number of cases as existed for car drivers in the 1992 Interim

Report). Only the 39 light-truck passengers are too few for any analysis.

The current study, as well as the two earlier ones, are statistical analyses. They look at large

numbers of crashes, in the aggregate, to compare the fatality rate in vehicles equipped with air bags

to the rate in comparable vehicles without air bags. They do not inspect the crashes one-by-one to

find out the mechanism of fatal injury, or how the air bag performed, or even if it deployed. We may

presume that a large proportion of the 9609 "fatalities at seating positions equipped with air bags"

involved injury mechanisms entirely unrelated to the air bag (the nonfrontal impacts, for example).

Conversely, when a person survives a crash at a seating position equipped with an air bag, the FARS

data do not tell us if the air bag was responsible for that individual's survival. All the data tell us is

whether vehicles equipped with air bags have lower fatality rates than comparable vehicles without

air bags and, all else being equal, the difference in the fatality rates can be attributed to the air bag.

The current population of vehicles equipped with driver air bags is not only much larger than it was

a few years ago; it is also far more representative. In model years 1985-88, air bags were primarily

installed in luxury cars such as Mercedes and BMW. By contrast, during 1989-90 manufacturers

concentrated on introducing air bags into sporty cars with a high proportion of young drivers (where

they were needed most), such as Dodge Daytona, Ford Mustang, Pontiac Firebird, Mazda Miata and

Toyota Celica. The first large company to install driver air bags in all of their new cars was Chrysler,

during 1988-90. Increasingly, they became standard on typical "family" cars such as Ford Taurus

(1990), Chevrolet Corsica (1991), Honda Accord and Toyota Camry (1992). By the end of model

year 1993, air bags were common in all market classes of cars. Over 80 percent of MY 94 cars and

over 95 percent of MY 95 cars had driver air bags. In early 1996, the cumulative roll, by

manufacturer, of occupant fatalities at seat positions equipped with air bags did not look too different

from the overall distribution of cars on the road in the United States:

General Motors

Honda/Acura

Mercedes

Mitsubishi

Subaru

Saab

Suzuki

2615

627

218

112

42

22

2

Ford

Toyota/Lexus

Mazda

Volvo

VW/Audi

Isuzu

2164

570

191

51

36

14

Chrysler

Nissan/Infiniti

BMW

Hyundai

Porsche

Jaguar

1602

256

112

48

25

8

Dual air bags were also initially installed in luxury cars, such as Porsche, Lincoln and Mercedes,

during 1987-91. These early installations, however, were few in number, and they account for only

about 20 percent of the passenger fatalities to date. Most of the data come from 1993-95 model cars.

When the shift from single to dual air bags began in 1993, it was rapid, and it tended to involve all

car lines at about the same time. That makes the dual air-bag cars with right-front passenger fatalities
quite representative of the late-model (1993-95) passenger car fleet.

Chrysler Corporation minivans, such as Dodge Caravan and Plymouth Voyager, were the first light

trucks equipped with driver air bags, on a partial basis in model year 1991 and as standard equipment

in 1992. That was four years in advance of the phase-in required by FMVSS 208. People who buy

minivans tend to be safety-conscious, since the vehicles are typically used for transporting families

and children. Thus, probably in response to consumer demand, other minivans also offered driver air

bags early: Ford Aerostar and Toyota Previa (1992), Mazda MPV (1993), GM Astro/Safari and

Nissan Quest (1994). Air bags did not appear in pickup trucks until 1994, and they were not installed

on the majority of pickup trucks and SUV until 1995. As a result, the 855 driver fatality cases are

not representative of the light-truck fleet, but include an overrepresentation of minivans. In 1994,

Chrysler Corporation minivans and Toyota Previa also became the first light trucks with standard dual

air bags; Ford Windstar and Isuzu Trooper followed in 1995.

Appendices A and B list the types of occupant protection installed in each make-model of passenger

cars and light trucks, by model year.

1.3 FARS data preparation

The Fatal Accident Reporting System (FARS) provides a census of fatalities in motor vehicle crashes

in the United States since 1975, including drivers and right-front passengers of passenger cars and

light trucks [9]. As of August 1996, the FARS file is essentially complete through 1995 and it

includes a substantial number of cases from the first quarter of 1996. The study is based on FARS

records of model year 1985-95 passenger cars involved in fatal crashes during calendar years 1986-

96, and model year 1989-95 light trucks in fatal crashes during calendar years 1988-96.

The first 10 characters of the Vehicle Identification Number (VIN) are listed for most of the vehicle

records on FARS. As in both previous evaluations of occupant protection, all information in this

study about the make, model, model year and type of occupant protection in a particular vehicle was

derived from analysis of the VTN, based on various sources in the literature [1], [3], [22], [23], [25].

A series of programs, written or updated by NHTS A staff for this evaluation, selects model year

1985-95 vehicles based on the 10th character of the VIN, identifies the manufacturer and make from

the first 3 characters and the specific model from characters 4-8 (and excludes trucks over 10,000

pounds Gross Vehicle Weight, motorcycles and other vehicles that are not cars or light trucks), and

classifies the type of occupant protection for the driver and the right-front passenger, based on

specific VIN characters and/or manufacturer-supplied information on what is standard equipment in

a given make-model-year (see Appendices A and B).

Vehicle records where the VIN was unreported were excluded from the study. VINs that could not

be deciphered to indicate the make-model and the type of occupant protection, either because of an

error in the reporting of the VEST or because the type of occupant protection is not decipherable from

the VIN, were also excluded. As an additional precaution, records were excluded if the FARSreported model year was inconsistent with the model year decoded from the 10th character of the

VIN. As a result, approximately 5J/2 percent of FARS records are excluded from the analysis:
0.9% Model year not reported on FARS

2.5% VIN not reported on FARS

1.0% FARS and VIN model years inconsistent

0.9% Error in VIN: could not determine manufacturer/make/model

0.3% Unknown occupant protection: error in VIN (cars), or not known from VTN (light trucks)

Each vehicle included in the analysis is classified by two four-digit codes derived from NHTSA's VTN

analysis: the fundamental car [or light truck] group (CG) and specific make-model (MM2). These

codes replace any make-model information already on FARS. Each car or light truck group

comprises one or more make-models sharing a body platform. For example, all GM N-body cars

(Buick Skylark, Oldsmobile Calais and Achieva, Pontiac Grand Am) belong to the same car group.

When a car or truck gets a major redesign, a new group is defined - e.g. Honda Accord in 1990, or

GM C/K pickups in 1988. Vehicles with a "shared body platform" belong to the same functional class

(car, pickup, SUV or van) and usually have the same wheelbase, track width and primary drive system

(front-wheel or rear-wheel). Different make-models in the same car group are sometimes nearly

identical "corporate cousins" (Ford Tempo and Mercury Topaz, Dodge Caravan and Plymouth

Voyager), or they may be recognizably different vehicles on the same platform (1985 Cadillac Seville

and Eldorado). It should be noted that the same make-model code may be used for two quite

different vehicles in two separate car groups, even in the same year, e.g., 1988 Buick LeSabre H-body

sedan or a B-body station wagon. (The specific make-model codes for passenger cars, but not trucks,

as shown in Appendix A, are usually, but not always identical to the codes of the pre-1991 FARS

variable MAK_M0D.)

The type of occupant protection is indicated by yet another 4-digit code. The first digit indicates if

an air bag was installed for the driver, the third digit, for the right-front passenger:

0 No air bag at that seat position

1 Air-bag equipped at that position

The second digit indicates the type of belt system for the driver, the fourth for the right-front

passenger:

0 Manual 3-point belt

3 Motorized 2-point belt without disconnect, plus manual lap belt

4 Motorized 2 point belt with disconnect, plus manual lap belt

5 Nonmotorized, door-mounted 3-point belt

6 Nonmotorized, door-mounted 2 point belt, plus manual lap belt

7 Nonmotorized, door-mounted 2 point belt, plus knee bolster (no lap belt)

Thus, for example, a code of 1004 indicates that a car is equipped with an air bag and manual 3-point

belt for the driver; no air bag, a motorized 2 point belt with disconnect, and a manual lap belt for the

right-front passenger. A code of "9" indicates unknown occupant protection system: those vehicles

are not included in any of the analyses.

Other variables are taken directly from the FARS records, such as the first harmful event and the
number of vehicles involved in the accident; the initial and principal damage location on the subject

vehicle (IMPACT1 and LMPACT2), and its most harmful event; and the injury severity, age, sex and

FARS-reported belt use of the driver and the right-front passenger. Even though the F ARS variables

IMPACT 1 and IMPACT2 use an "o'clock" reporting scheme, they indicate damage location, not

necessarily direction of force. Thus, IMP ACT2 = 1 indicates primary damage on the right-front

corner, but not necessarily with a 1:00 principal direction of force. Except for certain statistics in

Chapter 3, none of the analyses of this report rely on the FARS-reported belt use variable.

1.4 Definitions of "fatality reduction"

There are two separate ways to measure fatality reduction by air bags. The measure used in this

chapter and the next one is the net, overall "as used" fatality reduction. This is the average effect

of air bags for the entire population of occupants, including those who use their belts and those who

don't. For example, the fatality risk for all drivers of cars with driver air bags (some of whom

currently use the belts provided in those cars, some of whom do not) is compared to the risk for all

drivers of similar cars without air bags, but with the same belt systems at the same use rates. The

fatality reduction, or effectiveness, is the relative difference of the two risks. The effectiveness

estimate comprises all crashes: those where the bag deployed and those where it didn't.

NHTSA is also interested in obtaining two estimates of "when used" fatality reduction by air bags:

(1) Air bag effectiveness for unrestrained drivers: the relative difference between the

fatality risk of the unrestrained drivers of cars equipped with air bags and the

unrestrained drivers of similar cars without air bags.

(2) Air bag effectiveness for belted drivers: the relative difference between the fatality

risk of the belted drivers of cars equipped with air bags and the belted drivers of

similar cars without air bags - i.e., the relative incremental effect of belts plus bags

over belts alone.

The "as used" fatality reduction is essentially a weighted average of these two "when used" estimates.

The terms "as used" and "when used" pertain to the belt use of the occupants, not their "use" of the

air bags: in all cases, nondeployment as well as deployment crashes are included in the estimates.

The principal advantage of "as used" fatality reduction is that it is much easier to estimate accurately

from FARS data. All FARS cases are included in the analysis, regardless of whether the occupants

were belted or unrestrained. If we knew which of these occupants were actually belted and which

were unrestrained, we could split them into two groups according to their belt use, and compute the

two "when used" estimates. However, the consensus is that FARS does not necessarily contain

accurate information about the belt use of crash survivors, especially in recent years [24]. Chapter

3 describes several attempts to obtain approximate estimates of "when used" fatality reduction

without relying on FARS belt-use reporting for crash survivors or, preferably, for any of the

occupants.

The measure of fatality reduction in this report is, at first glance, quite different from NHTSA's two
previous evaluations. Those studies estimated the effect of the total occupant protection program:

lives saved by air bags plus lives saved by increases in belt use after 1983. The effectiveness

estimates, superficially, looked much higher in the earlier reports because the benefits of increased

belt use were added to the benefits of the air bags. On closer examination, however, the analytic

techniques of this report are nearly the same as in the two previous ones. In all cases, the primary

analysis estimated the incremental benefit of air bags plus belts, at current belt use rates, over belts

alone, at current use rates (and this reduction was 14 percent in the 1992 evaluation and 10 percent

in the 1994 paper). Subsequently, in the two earlier studies, an additional savings for the increase in

belt use from 1983 to the time of the study was merely "tacked on" to the primary estimate to obtain

the effect of the total occupant protection program since 1983 (which was a 23 percent reduction in

both studies). This study focuses exclusively on the benefits of air bags, not belts.

1.5 Fatality reduction for driver air bags - passenger cars

To compute fatality reduction, it says in the preceding section, the fatality risk for all drivers of cars

with driver air bags should be compared to the corresponding risk for all drivers of similar cars

without air bags. The key words that need more explanation are "risk" and "similar." Fatality "risk"

with air bags, throughout this report, is a ratio of fatalities: the number of deaths for a specific group

of occupants or crashes that could be affected by air bags divided by the number of fatalities of some

control group of occupants or crashes who will not likely be affected by the air bags. "Similar" cars

are the same makes and models as the air bag cars, in adjacent model years, and excluding makemodels that were substantially redesigned at the time they got air bags.

A principal task is to identify groups of crashes or occupants that will be helped by air bags as well

as control groups that are unlikely to be helped by air bags. One factor in the phase-in process for

FMVSS 208 aided the analysis. The regulation excluded the right-front passenger position from

automatic protection until September 1, 1993 in cars with driver air bags. Through model year 1993,

over 90 percent of the cars equipped with air bags had them only for the driver. In cars with driveronly air bags, the right-front passengers are a "control group": they are unlikely to be helped by the

[driver] bags.

The ratio of driver to right-front passenger fatalities in cars with driver air bags (in crash-involved

cars where both seats were occupied) is compared to the corresponding ratio in earlier cars of the

same makes and models, equipped only with belts at both positions. Cars in which the passenger was

less than 5 years old are not included in this analysis. The effectiveness of air bags is estimated by

the relative difference in the ratios. This procedure is called "double pair comparison analysis" [7].

The only real disadvantage of this method is that the analysis has to be limited to cars where both

seats are occupied (about 1/3 of the fatality data sample).

Table 1-1 lists make-models that had manual or automatic 3-point belts only, and then, at some point

during 1986-95, added driver air bags while retaining the 3-point belts. Make-models that always

had driver air bags are excluded from the analysis, since there are no corresponding cars without

them. Cars with dual air bags are excluded since the right-front passengers are not "a control group

unaffected by air bags." Cars with any kind of 2-point automatic belts are also excluded. If these
TABLE 1-1 - CAR DRIVERS: MAKE-MODELS THAT HAD MANUAL OR AUTOMATIC 3-POINT BELTS

AND ADDED DRIVER AIR BAGS WITHOUT CHANGING THE BELT SYSTEM

MODEL YEARS INCLUDED IN THE EFFECTIVENESS ANALYSES

Model Years with

Make-Model 3-Point Belts Only

Chrysler

Dodge

Plymouth

Ford

Lincoln

Mercury

Buick

Cadillac

Chevrolet

Geo

Oldsmobile

Pontiac

LeBaron

New Yorker C

Daytona

Diplomat

Dynasty

Omni

Shadow

Spirit

Acclaim

Gran Fury

Horizon

Sundance

Crown Victoria

Mustang

Taurus

Continental

Mark 7

Town Car*

Grand Marquis

Sable

Century*

Electra*

full-size wagon*

LeSabre*

ReatU

Regal*

Riviera***

Skylark

Allante

DeVille*

Eldorado***

Seville***

Beretta***

Camaro

Caprice*

Corsica***

Corvette

Spectrum, Storm

Achieva

Custom Cruiser*

Cutlass Ciera*

Cutlass Supreme*

Delta 88*

98*

Toronado***

Bonneville*

Firebird

Grand Am

1987-88

1989

1986-88

1988

1988-89

1989

1987-89

1989

1989

1988

1989

1987-89

1987-89

1988-89

1988-89

1988

1989

1988-89

1987-89

1988-89

1991-93

1988-90

1988-90

1989-91

1988-89

1993

1987-89

1992-93

1988-89

1987-89

1987-89

1987-89

1989-90

1988-89

1988-90

1989-90

1987-89

1987-89

1992-93

1989-90

1991-93

1992-93

1990-91

1989-90

1988-89

1990-91

1988-89

1992-93

Model Years with

Driver Air Bags

1988-90

1990-92

1988-90

1988-89

1990-91

1990

1990-92

1990

1990

1988-89

1990

1990-92

1990-92"

1990-92

1990-92"

1989-90"

1990-92

1990-91**

1990-92**

1990-92"

1993-95

1991-93

1991-92

1992-93

1990-91

1994

1990-92

1994-95

1990-93

1989-92

1990-92

1990-91

1991-93

1990-92

1991-93

1991-93

1990-92

1990-92

1994-95

1991-92

1993-95

1994

1990-93

1989-93

1990-92

1992-93**

1990-92

1994-95

Make-Model

VW

Audi

BMW

Nissan

Honda

Acura

Jaguar

Mazda

Mercedes

Saab

Toyota

Volvo

Cabriolet

Model Years with

3-Point Belts Only

1989

5000/100/200* 1988-89

80/90*

300

500

600

700

300ZX

Pulsar/NX

Sentra

Accord

Civic

Prelude*

Legend*

XJ-S*

RX7

1988-89

1988-89

1987-89

1987

1985-87

1990-91

1989

1993-94

1988-89

1989-91

1989-91

1986-88

1987-89

1989

basic sedan* 1985

190

S and SEL

1985

1985

SL Roadster 1985

900*

9000

Celica

Supra

MR-2

240*

740*

760*

1988-89

1987-89

1987-89

1989

1987-89

1988-89

1987-89

1985-87

Model Years with

Driver Air Bags

1990-92

1989-91

1990-92

1990-92

1989-91

1988-89

1987-88

1991-93

1990-92

1993-94

1991-93"

1992-93

1992-93**

1987-90

1990-92

1990-91

1986

1985-86

1985

1986

1990-92

1988-92

1990-92

1990-91

1991-93

1990-92

1987-92

1987-90

* Make-model(s) switched to ABS in the same year as air bags: excluded from the analysis of frontal vs. nonfrontal fatalities

** Some of the cars have dual air bags; these cars are excluded from the analyses

••* Make-model switched to ABS 1 -2 years before or after air bags: frontal-nonfrontal analysis limited to selected model years with the same

ABS status
cars switched from 2-point to 3-point belts when they got air bags, some of the change in the fatality

risk could be due to the change in the belts, not the air bags. But even if they kept the 2-point belts

while adding air bags (as was not unusual in 1993-94), this is a configuration that will soon be phased

out and is not characteristic of the future vehicle fleet. Automatic 3-point belts, on the other hand,

were included in the analysis. Their use rates and other characteristics are close enough to manual

3-point belts that they may be considered essentially the same thing, at least for statistical analyses

of overall air-bag effectiveness [6], [19].

Table 1-1 shows the ranges of model years used in the analysis. The maximum range permitted was

6 model years - the first 3 years with air bags, vs. the last 3 years without them - but in most cases

a shorter range was selected. The purpose of limiting the model-year range is to prevent excess

disparity in vehicle ages between the air-bag equipped and the belt-only cars. As cars get substantially

older, their distribution of accident types changes, possibly biasing the analyses (but not so much in

this case, since most vehicle-age biases would have about the same effect on the driver and the rightfront passenger fatalities). If a make-model was introduced, discontinued, or substantially redesigned

less than 3 years before or after the switch to driver air bags, the range has to be cut off at that point.

A final criterion for selecting the range is to assure that each make-model has an accident sample of

belt-only cars as close as possible to double its air-bag equipped sample. A uniform ratio of belt-only

to air-bag cars, by make-model, assures that the belt-only and air-bag samples have a similar makemodel mix (thereby avoiding, for example, a bias due to an overrepresentation of sporty cars in one

group or the other). In this particular data set, a target ratio of two belt-only cars to one air-bag

equipped car is, heuristically, the best: a smaller ratio would increase sampling error because it would

reduce the sample of belt-only cars; a larger ratio cannot be achieved, in many make-models, without

using more than 3 model years of belt-only cars, increasing the possibility of vehicle-age biases.

Table 1-2 computes the fatality reduction with driver air bags in passenger cars. There were 2516

driver fatalities and 2715 right-front passenger fatalities in the cars with 3-point belts only, a risk ratio

of .927. In other words, without air bags, fatality risk for the driver is just slightly less than for the

right-front passenger. But in the matching make-models equipped with driver air bags, there were

only 1313 driver fatalities (with air bags) as opposed to 1567 right-front passenger fatalities (without

air bags), a risk ratio of .838. That is a 10 percent reduction in the fatality risk ratio associated with

driver air bags, and it is statistically significant at the .05 level: Chi-square (x2) for the 2 x 2 table is

4.69 (x2 has to be at least 3.84 for significance at the .05 level and 6.64 for significance at the .01

level. If air bags had no effect at all, we would hypothesize the same distribution of front-outboard

fatalities, by seat position, in the belt-only and air bag-equipped cars; the x

2

 test for the 2 x 2 table

of front-outboard fatalities by type of occupant protection and seat position tests the null hypothesis.)

Another distinctive characteristic of air bags, which leads to a second method for estimating

effectiveness, is that they are primarily designed to deploy in impacts with a frontal or partially frontal

direction of force. If an impact has no frontal force component, the air bag would not usually deploy

and cannot be expected to have much effect on fatality risk. The fatalities in purely nonfrontal crashes

act as a control group relative to the fatalities in frontal or partially frontal crashes. It is appropriate

to use an inclusive definition of "frontal and partially frontal" crashes, encompassing even crashes

with a modest frontal force component: crashes in which the initial and/or principal impact location

is anywhere between 10.00 and 2:00 on FARS. (The inclusive definition of frontals was originally
TABLE 1-2 - CAR DRIVERS: EFFECTIVENESS OF DRIVER AIR BAGS

BASED ON REDUCTION OF DRIVER FATALITIES

RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

(both seats occupied; make-models that had manual or automatic

3-point belts and added driver air bags without changing the belt system)

Driver Right Front Risk Percent

Fatalities Fatalities Ratio Reduction

Cars with belts only 2516 2715 .927

Cars w. driver air bags 1313 1567 .838 10

(statistically significant difference: X2 - 4.69)

TABLE 1-3 - CAR DRIVERS: EFFECTIVENESS OF DRIVER AIR BAGS

BASED ON REDUCTION OF FRONTAL FATALITIES

RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

Nonfrontal fatalities 1841 1121

Frontal fatalities 3422 1691 19

(statistically significant difference: x2 = 18.33)

Fatality reduction for driver air bags in all types of crashes: 12 percent

10
recommended by the Insurance Institute for Highway Safety in their October 1991 analysis of the

fatality reduction for driver air bags in passenger cars [29].) "Nonfrontal" crashes include side and

rear impacts (principal impact 3:00-9:00), rollovers and other noncollisions (as defined by their most

harmful event) without a 10:00-2:00 initial or principal impact. (Collisions with unknown impact

locations are excluded from the analysis.) The ratio of frontal to nonfrontal driver fatalities in cars

with driver air bags ought to be lower than the corresponding ratio in earlier cars of the same makes

and models, equipped only with 3-point belts. The effectiveness of air bags in frontal crashes is

estimated by the relative difference in the ratios. This analysis has the disadvantage of relying on the

assumption of zero effectiveness in nonfrontal crashes, but it allows a larger sample size than the

preceding method (since it is not limited to cases where the right-front seat was occupied); however,

with the narrow definition of "nonfrontal crashes" used here, we can be reasonably confident that

these crashes are a true control group for air bags, except to the extent (if any) that impact locations

might be grossly misreported in FARS.

Table 1-1 lists make-models that switched from 3-point belts only to driver air bags plus 3-point belts

at some time during 1986-95. However, not all of these models are appropriate for the current

analysis. Make-models that received Antilock Brake Systems (ABS) on all or most of the cars,

simultaneous with or close to the switch to air bags must be excluded. Studies have shown that ABS

is associated with a shift from frontal to nonfrontal fatal crashes [16], [20]. Drivers of cars with ABS

are experiencing some reductions in frontal collisions with other vehicles and substantial increases in

nonfrontal single-vehicle crashes such as rollovers and side impacts with fixed objects. If cars that

got air bags and ABS at the same time were included in the analysis, the effect associated with current

ABS systems (an increase in nonfrontal fatalities) would be mistakenly interpreted as a benefit for air

bags (a reduced proportion of frontal relative to nonfrontal fatalities). The analysis has to be limited

to make-models that never had ABS (e.g., Dodge Omni), or became equipped with ABS well before

air bags (e.g, BMW 300) or well after (e.g., Chevrolet Camaro). Table 1-1 shows that some models

are excluded entirely, because they got air bags and ABS at the same time. Others are included for

just a limited range of model years, before and after the shift to air bags, during which their ABS

status did not change. Quite a few models, especially General Motors and Volvo, are fully or partially

excluded.

Table 1-3 presents the data needed to calculate the fatality reduction for driver air bags in frontal

crashes, and overall. There were 3422 frontal driver fatalities and 1841 nonfrontal driver fatalities

in the cars equipped only with 3-point belts. But in cars with air bags, there were only 1691 frontal

driver fatalities as opposed to 1121 nonfrontal driver fatalities. This is evidently a substantial

reduction in the ratio of frontal to nonfrontal fatalities. The relative reduction of frontal fatalities for

driver air bags is

1 - [(1691/1121)/(3422/1841)] = 19 percent

and it is statistically significant at the .01 level (x2 = 18.83; if air bags had no effect at all, we would

hypothesize the same distribution of driver fatalities, by impact location, in the belt-only and air bagequipped cars; the x

2

 test for the 2 x 2 table of driver fatalities by type of occupant protection and

impact location tests the null hypothesis.). Given that air bags reduce fatalities by 19 percent in

frontal crashes and have little effect in nonfrontal crashes, the overall fatality reduction for driver air

bags is the weighted average of 19 and zero:

(1 - [(1691/1121) / (3422/1841)]} [3422 / (3422+1841)] = 12 percent

11
In summary, two rather different methods for computing the fatality reduction for driver air bags in

passenger cars yielded nearly identical results: 10 and 12 percent. In both analyses, the reduction was

statistically significant. Given the consistency of the two results, their simple arithmetic average is

probably the "best" estimate, at least in a heuristic sense: an 11 percent reduction of car driver

fatalities by air bags.

An approximate sense of sampling errors and confidence bounds may be developed from the entries

in Table 1-3, the table that includes the largest number of accident cases. The four numbers in the

table, an, a12, a^ and a^, are counts of fatalities in different vehicle types and crash modes, and they

can be considered independent Poisson variates. The effectiveness statistic in frontal crashes

E = 1-R = l-Kaa/a^/CajAi)]

is based on a ratio of ratios, R, with approximate variance

V(R) = R2 [l/an + 1/ ^ + l/oj, + 1/aJ

In Table 1-3, where R = .81 and the table entries are 1841, 1121, 3422 and 1691, the standard

deviation of effectiveness in frontal crashes is approximately

.81 [1/1841 + 1/1121 + 1/3422 + 1/1691]

 5

 = .0390

With the assumption that air bags have no effect in nonfrontal crashes, and with only trivial

uncertainty about the proportion of fatalities in belt-only cars that is frontal, the standard deviation

of effectiveness for all types of crashes is

.0390 [3422 / (1841 + 3422)] = .0254

Taking 1.645 standard deviations on either side of the "best" estimate of 11 percent yields

approximate confidence bounds (two-sided a = .05, i.e., 90 percent bounds):

.11 ± 1.645 x .0254 = 7 to 15 percent fatality reduction

The 11 percent fatality reduction for driver air bags in passenger cars is almost identical to what was

found in the two previous NHTSA evaluations. In the 1992 Interim Report, the analysis of driver

vs. right-front passenger fatalities found "an 11 percent fatality reduction for driver air bags relative

to manual belts at current use rates" [6], p. 22. (The analysis of frontal vs. nonfrontal fatalities found

an overall reduction of 13 percent for air bags relative to manual-belt cars at current use rates, but

this finding is biased in favor of air bags, because cars that switched to ABS at the same time as air

bags were not excluded from the analysis [6], p. 24.) In the 1994 ESV paper, the analysis of driver

vs. right-front passenger fatalities found an 8 percent reduction for air bags relative to manual belts

at current use rates, and the frontal vs. nonfrontal analysis indicated a 12 percent reduction: these two

findings average out to a 10 percent reduction [19].

1.6 Fatality reduction for driver air bags - light trucks

The same analysis procedures - comparison of driver and right-front passenger fatalities, and

comparison of frontal and nonfrontal fatalities - can be used to estimate fatality reduction for driver

air bags in light trucks (vans, pickup trucks and SUV). Table 1-4 lists the models that switched from

manual 3-point belts only to a driver air bag plus manual belts at some point during 1991-95. Table

1-4 also shows the ranges of model years used in the analysis. In general, the range is cut off when

a make-model was substantially redesigned less than 3 years before or after the switch to driver air

bags, but some exceptions were permitted to keep up the sample size: the Dodge D/W pickup was

included even though it was significantly redesigned at the same time it got driver air bags, because

12
TABLE 1-4 - LIGHT TRUCK DRIVERS: MAKE-MODELS THAT HAD MANUAL 3-POINT BELTS

AND ADDED DRIVER AIR BAGS WITHOUT CHANGING THE BELT SYSTEM

MODEL YEARS INCLUDED IN THE EFFECTIVENESS ANALYSES

Make-Model

Chrysler

Dodge

Jeep

Plymouth

Ford

Chevy/GMC

Oldsmobile

Pontiac

Mazda

Toyota

Mitsubishi

Town & Country

Caravan/Grand Caravan

Dakota

Ram pickup

Ram van/wagon

Cherokee

Voyager/Grand Voyager

Aerostar**

Bronco*

F pickup

F supercab pickup

Full-sized van/wagon

Ranger

Astro/Safari van

10/20 cargo vans

10 Sportvan/Rally

C/K pickup*

C/KlOOxtdcab*

Lumina APV

S/T Blazer/Jimmy

S/T pickup

Suburban

Silhouette

TransSport

MPV

Previa

T-100 pickup

Montero*

Model Years with

Manual Belts Only

1990

1989-90

1992-93

1991-93

1994

1994

1989-90

1989-91

1992-93

1991-93

1994

1992

1994

1992-93

1992-93

1992-93

1994

1994

1992-93

1994

1993-94

1994

1992-93

1992-93

1991-92

1991

1993

1991-93

Model Years with

Driver Air Bags

1992-93

1992-93

1994-95

1994-95

1995

1995

1992-93

1992-94

1994-95

1994-95

1995

1995

1995

1994-95

1994-95

1994-95

1995

1995

1994-95

1995

1995

1995

1994-95

1994-95

1993-95

1992-93

1994-95

1994-95

**

Make-model(s) switching from rear-wheel to four-wheel Antilock Brake Systems at about the same time

as they were equipped with air bags: excluded from the analysis of frontal vs. nonfrontal fatalities

Switched to rear-wheel ABS in 1990. frontal-nonfrontal analysis limited to model years 1990-93

13
it provides a substantial proportion of the pickup-truck data. The range of model years was also

tailored to assure that each make-model has a belt-only accident sample as close as possible to 2.5

times its air-bag equipped sample. That target ratio is, heuristically, the best: a smaller ratio would

increase sampling error because it would reduce the sample of belt-only trucks; a larger ratio cannot

be achieved, in many make-models, without using more than 3 model years of belt-only trucks.

Table 1-4 notes that certain trucks changed their ABS status at some time during the applicable

model-year range. Those models are excluded from the frontal-nonfrontal analysis, or included for

a shorter range of model years (although there is little evidence, so far, that either two-wheel or fourwheel ABS has the same effect in trucks as in cars [15], or that inclusion of these models would have

biased the analysis).

Table 1-5 analyzes the fatality reduction with driver air bags in light trucks, based on the comparison

of driver and right-front passenger fatalities. In the selected make-models, there were 478 driver

fatalities and 512 right-front passenger fatalities in the trucks equipped only with manual belts, a risk

ratio of .934. In the trucks of the same make-models equipped with driver air bags, there were 215

driver fatalities (with air bags) as opposed to 241 right-front passenger fatalities (without air bags),

a risk ratio of .892. That is a 4 percent reduction in the fatality risk ratio associated with air bags.

The effect is not statistically significant (x2 = 0.16).

Table 1-6 calculates the fatality reduction for driver air bags in frontal relative to nonfrontal crashes,

and overall. There were 1009 frontal and 410 nonfrontal driver fatalities in the trucks equipped only

with manual belts. But in trucks with air bags, there were 394 frontal as opposed to 208 nonfrontal

driver fatalities. The relative reduction of frontal fatalities for driver air bags is

1 - [(394/208) / (1009/410)] = 23 percent

and it is statistically significant at the .05 level (x2 = 6.37). Given that air bags reduce fatalities by

23 percent in frontal crashes and have little effect in nonfrontal crashes, the overall fatality reduction

for driver air bags is:

{1 - [(394/208) / (1009/410)]} [1009 / (1009 + 410)] = 16 percent

The average of the results of the two analyses for light trucks, 10 percent, is similar to the effect

found in passenger cars (11 percent).

1.7 Fatality reduction for passenger air bags - car passengers age 13 or older

Table 1-7 lists make-models that switched from a driver air bag plus manual or automatic 3-point

belts to dual air bags plus 3-point belts at some point during 1989-95 and it shows the ranges of

model years used in the analyses of the effectiveness of passenger bags. Models that had 2-point

automatic belts before and/or after the switch to dual air bags, or that switched directly from no air

bags to dual air bags are excluded. The criteria for accepting a make-model are a bit more lenient

here than in the analyses of car driver air bags (Table 1-1), because the available number of accident

cases is small and should not be further diminished if possible. For example, Ford Mustang, Honda

Accord and Saab 900, among others, were included even though they were significantly redesigned

at the time they got dual air bags; Dodge full-sized cars are treated as a single make-model even

though the Dynasty (driver air bag) and Intrepid (dual air bag) are not identical cars. (In future

studies, as the available pool of data grows, models like these will be dropped from the analysis.) The

range of model years was also tailored to assure that each make-model has a driver-bag equipped

14
TABLE 1-5 - LIGHT TRUCK DRIVERS: EFFECTIVENESS OF DRIVER AIR BAGS

BASED ON REDUCTION OF DRIVER FATALITIES

RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

(both seats occupied; make-models that had manual 3-point belts

and added driver air bags without changing the belt system)

Driver Right Front Risk Percent

Fatalities Fatalities Ratio Reduction

Trucks with belts only 478 512 .934

Trucks w. driver air bags 215 241 .892

(not a statistically significant difference: x

2 = 0.16)

TABLE 1-6 - LIGHT TRUCK DRIVERS: EFFECTIVENESS OF DRIVER AIR BAGS

BASED ON REDUCTION OF FRONTAL FATALITIES

RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual 3-point belts and

added driver air bags without changing the belt system;

excludes make-models that changed ABS status at the time they got air bags)

Trucks with Trucks with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

Nonfrontal fatalities 410 208

Frontal fatalities 1009 394 23

(statistically significant difference: x2 *= 6.37)

Fatality reduction for driver air bags in all types of crashes: 16 percent

15
TABLE 1-7 - CAR PASSENGERS: MAKE-MODELS THAT HAD DRIVER AIR BAGS WITH

MANUAL/AUTOMATIC 3-POINT BELTS

AND SWITCHED TO DUAL AIR BAGS WITHOUT CHANGING THE BELT SYSTEM

MODEL YEARS INCLUDED IN THE EFFECTIVENESS ANALYSES

Model Years with

Make-Model Driver Air Bags

Chrysler

Dodge

Ford

Lincoln

Mercury

Buick

Cadillac

Chevrolet

Geo

Oldsmobile

Pontiac

5thAve*/LH*

LeBaron

Dynasty/Intrepid*

Stealth

Crown Victoria

Mustang

Probe

Taurus

Mark7/8

Town Car*

Grand Marquis

Sable

Electra

LeSabre***

Regal

Riviera

Roadmaster

DeVille

Eldorado***

Seville***

Camaro*

Caprice

Corvette

Prizm

Cutlass Supreme

Delta 88

98

Bormeville***

Firebird*

1990-93

1991-93

1991-93

1993

1991-93

1992-93

1993

1990-93

1990-92

1990-91

1990-92

1990-92

1992-93

1992-93

1994

1991-93

1993

1992-93

1990-92

1990-92

1990-92

1992-93

1992-93

1993

1994

1992-93

1992-93

1992-93

1990-92

Model Years with

Dual Air Bags

1993-95

1994-95

1993-95

1994-95

1992-95

1994-95

1994-95

1992-95

1993-95

1990-92

1992-95

1992-95

1994-95

1994-95

1995

1995

1994-95

1993-95

1993-95

1993-95

1993-95

1994-95

1994-95

1994

1995

1994-95

1994-95

1992-95

1993-95

Make-Model

Audi

BMW

Nissan

Infiniti

Honda

Acura

Jaguar

Mazda

Mercedes

Saab

Subaru

Toyota

Lexus

Volvo

Mitsubishi

100/200

300

500

700

850

Sentra

300ZX

M30/J30

Q45

Accord

Civic

Del Sol

Prelude

Legend

NSX

Vigor

XJ

XJ-S

Miata

MX6/626

RX7

basic sedan

S and SEL

SL Roadster

900

Impreza

Camry

Celica*

Corolla

Supra

ES300

LS400

SC300/400

940

960

3000GT

Diamante*

Model Years with

Driver Air Bags

1991-92

1991-93

1992-94

1990-92

1991-92

1993-94

1992-93

1990-92

1991-93

1991-93

1992-93

1993

1992-93

1988-92

1991-92

1992-93

1993-94

1990-93

1992-93

1993

1993

1989-92

1987-91

1987-90

1992-94

1993-94

1992-93

1992-93

1993

1990-93

1992-93

1992

1992

1991-93

1991-92

1991-93

1993

Model Years with

Dual Air Bags

1992-95

1994-95

1994-95

1993-95

1993-95

1995

1994-95

1993-95

1994-95

1993-95

1994-95

1993-95

1992-95

1991-94

1993-95

1993-94

1994-95

1994-95

1994-95

1994-95

1994-95

1989-93

1989-91

1990-92

1994-95

1995

1994-95

1994-95

1994-95

1994-95

1994-95

1993-95

1993-95

1994-95

1993-95

1994-95

1994-95

Make-model(s) switched to ABS in the same year as dual air bags: excluded from the analysis of frontal vs. nonfrontal fatalities

Make-model switched to ABS 1-2 years before or after dual air bags: frontal-nonfrontal analysis limited to selected model years with the

same ABS status

16
accident sample as close as possible to double its dual-bag sample. That target ratio is, heuristically,

the best: a smaller ratio would increase sampling error because it would reduce the sample of driverbag cars; a larger ratio cannot be achieved, in many make-models, without using more than 3 model

years of driver-bag cars. Table 1-7 shows that a few models are excluded entirely from the analysis

of frontal vs. nonfrontal crashes, because they got dual air bags and ABS at the same time. Others

are included for just a limited range of model years, before and after the shift to dual air bags, during

which their ABS status did not change.

Unlike the driver population, right front passengers include infants and small children as well as

teenagers and adults. There is extensive evidence from individual crash investigations, however, that

child passengers, possibly up through age 12, are encountering unique hazards in their interactions

with air bags that could cancel out their benefits or even result in higher fatality risk [14], [28]. There

is reason to suspect the effect of passenger air bags could be quite different for children than for

teenagers and adults. In this chapter, let us remove the relatively few records involving child

passengers from the accident sample and concentrate on the passengers age 13 or older.

The comparison of driver and right-front passenger fatalities is carried out in reverse to estimate

fatality reduction for passenger air bags. Now, the drivers (with driver air bags) are the "control

group": they get no help from the passenger bags. The ratio of right-front passenger fatalities (age

13 or older) to driver fatalities in cars with dual air bags (in crash-involved cars where both seats

were occupied by people age 13 or older) is compared to the corresponding ratio in earlier cars of

the same makes and models, equipped only with driver air bags. The effectiveness of passenger air

bags is estimated by the relative difference in the ratios. Table 1-8 analyzes the fatality reduction with

passenger air bags, based on this method. In the selected make-models, there were 1043 right-front

passenger fatalities and 823 driver fatalities in the cars equipped only with driver air bags and belts,

a risk ratio of 1.267. In other words, the passenger, with no air bag, is at substantially higher risk

than the driver, with an air bag. In the same make-models equipped with dual air bags, there were

501 right-front passenger fatalities and 475 driver fatalities, a risk ratio of 1.055 - i.e., a return to the

slight disadvantage of the right-front seat relative to the driver seat, as was the case before either was

equipped with air bags. That is a statistically significant 17 percent overall fatality reduction for

passenger air bags when risk is measured relative to driver fatalities (x2 = 5.38, p < .05).

The analysis of frontal vs. nonfrontal right-front passenger fatalities is the same as for drivers. Table

1-9 shows that there were 448 frontal and 332 nonfrontal right-front passenger fatalities in the cars

equipped only with driver air bags. In cars with dual air bags, there were 182 frontal as opposed to

165 nonfrontal driver fatalities. The relative reduction of frontal fatalities for passenger air bags is

1 - [(182/165) / (448/332)] = 18 percent

and it is not statistically significant (x2 = 2.42). If passenger air bags reduce fatalities by 18 percent

in frontal crashes and have little effect in nonfrontal crashes, the overall fatality reduction is:

{1 - [(182/165) / (448/332)]} [448 / (448+332)] = 10 percent

The results of the two analyses average out to a fatality reduction of 13.5 percent for passengers age

13 or older, in all types of crashes, which is quite similar to the effect found for driver air bags in

passenger cars (11 percent).

17
TABLE 1-8 - CAR PASSENGERS AGE 13 OR OLDER:

EFFECTIVENESS OF PASSENGER AIR BAGS, BASED ON REDUCTION OF

RIGHT FRONT PASSENGER FATALITIES RELATIVE TO DRIVER FATALITIES

(both seats occupied; make-models that had driver air bags with manual/automatic 3-point belts

and switched to dual air bags without changing the belt system)

Right Front Driver Risk Percent

Fatalities Fatalities Ratio Reduction

Cars w. driver air bags 1043 823 1.267

Cars w. dual air bags 501 475 1.055 17

(statistically significant difference: x2 = 5.38)

TABLE 1-9 - CAR PASSENGERS AGE 13 OR OLDER:

EFFECTIVENESS OF PASSENGER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had driver air bags with manual/automatic 3-point belts

and switched to dual air bags without changing the belt system;

excluding make-models that got ABS at the same time as dual air bags)

Cars with Cars with Frontal Fat. Red.

Driver Air Bags Dual Air Bags for Passenger Bag (%)

Nonfrontal fatalities 332 165

Frontal fatalities 448 182 18

(not a statistically significant difference: x

2 = 2.42)

Fatality reduction for passenger air bags in all types of crashes: 10 percent

18
1.8 Estimated increase of fatalities, through 1995, if there had been no air bags

Given that driver air bags in passenger cars reduce fatalities by 11 percent (and assuming a similar

effectiveness for car passengers and in light trucks), it is possible to infer, from the number of

fatalities that have actually occurred at seating positions equipped with air bags, how many

additional fatalities would have occurred if those vehicles had not been equipped with air bags.

Table 1-10 presents the estimates. The left column of the table shows the cumulative total of

fatalities at seat positions equipped with air bags, including drivers and right-front passengers in cars

and light trucks, that were identified in FARS. The cumulative total of fatalities has grown from 109

as of 12/31/89 to 8688 through 12/31/95.

But the number of identified fatalities on FARS understates the actual fatality total. As explained

in Section 1.3, approximately 5.5 percent of vehicle records on FARS were excluded from the

analysis because the VIN was unreported or incorrectly reported, the model year was unknown, etc.

Assuming that these excluded vehicles have the same proportion of air bags as the included ones, the

actual fatalities can be estimated by dividing the identified total by (1 - .055), as shown in the second

column of Table 1-10. Thus, by the end of 1995, the 8688 fatalities identified on FARS can be

assumed to correspond to 9194 actual fatalities.

If the fatality reduction for air bags is 11 percent, these numbers of actual fatalities would have been

higher if cars and light trucks had not been equipped with air bags. The 9194 fatalities at the end of

1995 would have increased to 9194 / (1 -. 11) = 10,330. Thus, an additional 10,330 - 9194 = 1136

fatalities would have occurred, cumulative through 1995, if cars and light trucks had never been

equipped with air bags. Given that the confidence bounds for fatality reduction are 7 to 15 percent

(see Section 1.5), the confidence bounds for the increase in fatalities, if cars and light trucks had not

been equipped with air bags, range from 692 to 1622 lives.

The 8688 fatalities identified on FARS include 675 right-front passengers age 13 or older in cars or

light trucks equipped with dual air bags. Dividing by (1 - .055), as a correction for missing data,

suggests that the 675 passenger fatalities identified on FARS correspond to 714 actual fatalities. If

the fatality reduction by air bags is about the same for passengers age 13 or older as it is for drivers,

11 percent, these 714 actual fatalities would have increased to 714/(1 -.11) = 802. Thus, an

estimated 802 - 714 = 88 additional fatalities would have occurred among right-front passengers age

13 or older, cumulative through 1995, if no cars or light trucks had been equipped with dual air bags.

1.9 Summary of fatality reduction estimates

Table 1-11 summarizes the estimates of overall fatality reduction for driver and passenger air bags.

The effectiveness of driver air bags in passenger cars was estimated by two analysis methods. Each

yielded a statistically significant fatality reduction: the first method 10 percent, the second, 12 percent.

We can be reasonably confident that the actual fatality reduction for car driver air bags is close to 11

percent, the average of the results by the two methods (confidence bounds for this reduction were

estimated to be 7 to 15 percent, in Section 1.5).

The two analyses for driver air bags in light trucks, working with a much smaller data sample, gave

19
TABLE 1-10

ESTIMATE OF CUMULATIVE INCREASE IN FATALITIES IF THERE HAD BEEN

NO DRIVER OR PASSENGER AIR BAGS IN CARS OR LIGHT TRUCKS

Cumulative Fatalities at Seat

ositions Equipped with Air Bags

Identified Actual

on FARS (Estimated*)

109

390

924

1709

3037

5153

8688

115

413

978

1808

3214

5453

9194

Cumulative

Additional

Fatalities If

There Had Been

No Air Bags§

14

51

121

223

397

674

1136

12/31/89

12/31/90

12/31/91

12/31/92

12/31/93

12/31/94

12/31/95

* Assuming 5.5% of fatal cases cannot be identified on FARS due to missing VINs, etc.

§

 Assuming 11% fatality reduction for all types of air bags

20
TABLE 1-11

ESTIMATES OF OVERALL FATALITY REDUCTION FOR AIR BAGS

Percent Fatality Reduction

Analysis Method

Driver air bags for cars

Driver air bags for light trucks

Passenger air bags for cars

(passengers age 13 or older)

Compare

Driver to

Right Front*

10

4

17

Compare

Frontal to

Nonfrontal*

12

16

10

Aver;

11

10

13

*Statistically significant results are shown in bold italics.

21
estimates of 4 percent and 16 percent. The second reduction is statistically significant. The results

average to 10 percent, nearly identical with the fatality reduction for driver air bags in passenger cars.

The analyses for passenger air bags in cars, limited to passengers age 13 or older, produced overall

fatality reductions of 17 percent and 10 percent, respectively. The first of these is statistically

significant. The average of the two results, 13.5 percent, is nearly identical to the reduction for driver

air bags in cars.

22
CHAPTER 2

FATALITY REDUCTION BY TYPE OF CRASH, VEHICLE OR OCCUPANT

2.1 By impact location

One of the principal findings of the 1994 NHTSA staff analysis of occupant protection [19] was that

driver air bags reduced fatalities in passenger cars by approximately 30 percent in impacts with purely

frontal damage (12:00 principal impact on the Fatal Accident Reporting System) but had little effect,

if any, in impacts with front-corner or front-side damage (10, 11, 1 or 2 o'clock principal impact on

FARS). The much larger accident data set now available enables us to update that analysis and to

take a first look at these effects for driver air bags in light trucks and passenger air bags in cars.

Table 2-1 examines the fatality reduction for driver air bags in cars, based on a comparison of driver

and right-front passenger fatalities in the cars. That analysis method, and the list of make-models

included in the analysis, are defined in Section 1.5. The top section of Table 2-1 addresses "purely

frontal" crashes in FARS: crashes with a 12:00 principal impact location, and in which the most

harmful event is not a rollover. Note that a 12:00 principal impact location does not necessarily mean

a 12:00 Principal Direction of Force (a variable not reported on FARS). The damage has to be in

the front of the car, even though the force could come from a partly oblique direction (conversely,

impacts with a 12:00 PDOF that result in front-corner or sideswipe damage are excluded).

Driver air bags are quite effective in purely frontal impacts. There were 825 driver fatalities and 867

right-front passenger fatalities in the cars with 3-point belts only, a risk ratio of .952. In other words,

without air bags, fatality risk for the driver is just slightly less than for the right-front passenger in a

pure frontal. But in the matching make-models equipped with driver air bags, there were only 313

driver fatalities (with air bags) as opposed to 498 right-front passenger fatalities (without air bags),

a risk ratio of .629. That is a 34 percent reduction in the fatality risk ratio associated with driver air

bags, and it is statistically significant at the .01 level (x2 = 23.55).

The second section of Table 2-1 analyzes "partially frontal" crashes: all impacts, except the purely

frontal ones, in which the initial or principal damage (or both) was between 10:00 and 2:00. This

category includes some impacts that are primarily frontal in nature, such as principal impacts to the

front corners (11:00 and 1:00). Also included are crashes where the frontal component is of

secondary importance, such as side impacts toward the front of the car (10:00 and 2:00), frontal

impacts followed by a most-harmful-event rollover, and multiple impacts in which the initial damage

is frontal but the principal damage is not. The fatality risk ratio is essentially the same without air

bags (.941) and with a driver air bag (.956). The observed effect for driver air bags is a 2 percent

increase in fatality risk, and it is not statistically significant (x2 = 0.26).

When the data for "purely frontal" and "partially frontal" crashes are combined, as shown in the third

section of Table 2-1, the net effect for driver air bags is in between the two preceding results: an 18

percent fatality reduction in all frontal crashes, statistically significant at the .01 level (x2 = 10.40).

23
TABLE 2-1 - CAR DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

(both seats occupied; make-models that had manual or automatic

3-point belts and added driver air bags without changing the belt system)

Driver Right Front Risk Percent

Fatalities Fatalities Ratio Reduction

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Cars with belts only 825 867 .952

Cars w. driver air bags 313 498 .629 34

(statistically significant difference: %2 = 23.85)

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only 698 742 .941

Cars w. driver air bags 390 408 .956 -2

(not a statistically significant difference: x

 2

 ~ 0.26)

IN ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Cars with belts only 1523 1609 .947

Cars w. driver air bags 703 906 .776 18

(statistically significant difference: x2 = 10.40)

IN NONFRONTAL CRASHES

Cars with belts only 960 1079 .890

Cars w. driver air bags 595 644 .924 -4

(not a statistically significant difference: x

2 = 0.27)

24
The last section of Table 2-1 is limited to nonfrontal crashes, in which the initial and principal impacts

are both in the 3:00 - 9:00 range, or in which there was no collision at all (e.g., rollovers, immersions

and fires without impact). Ideally, the data ought to indicate a zero effect for air bags here, since

these crashes would generally not result in an air bag deployment; actually the data show a 4 percent

increase with driver air bags that is not significantly different from zero (x2 = 0.27) and is very much

within the "noise" range, given the number of cases available for the statistical analysis.

Table 2-2 computes the fatality reduction in various subsets of frontal crashes by comparing them to

a control group of nonfrontal crashes. That analysis method is documented in Section 1.5 and Table

1-3; the control group is the same in each case. The top section of Table 2-2 shows that there were

1905 purely frontal driver fatalities and 1841 nonfrontal driver fatalities in the cars equipped with just

3-point belts. But in cars with air bags, there were only 847 purely frontal driver fatalities as opposed

to 1121 nonfrontals. In other words, there used to be slightly more pure-frontal than nonfrontal

fatalities, but with air bags, there are now substantially fewer. The relative reduction of purely frontal

fatalities for driver air bags,

1 - [(847/1121) / (1905/1841)] = 27 percent

is statistically significant at the .01 level (x2 =31.57). (Even though the observed effect is slightly

lower than the 34 percent in Table 2-1, the x

2

 statistic is higher because the analysis is based on a

larger number of accident cases.)

The middle section of Table 2-2 indicates a 9 percent fatality reduction for air bags in partially frontal

crashes. While that is better than the -2 percent effect in Table 2-1, it still appears negligible in

comparison to the effect in pure-frontal crashes, and it is not statistically significant (x2 = 2.48). The

net effect of air bags in all frontal and partially frontal crashes is an 19 percent reduction, and it is

statistically significant at the .01 level (x2 = 18.83). Unlike Table 2-1, this method will not compute

the fatality "reduction" for air bags in nonfrontal crashes; those crashes are a control group here, and

the fatality reduction is assumed to be zero.

While Tables 2-1 and 2-2 obviously suggest that driver air bags are more effective in purely frontal

than in partially frontal crashes, it would be desirable to confirm that conclusion by a statistical test.,

specifically, a x

2

 test on the 2 x 2 table of purely vs. partially frontal impact fatalities, gleaned from

Table 2-2:

Purely frontal

Partially frontal

No Air Bags

1905

1517

Air Bags

847

844

Since x

2 = 14.18 exceeds the quantity required for statistical significance at the .01 level, it may be

inferred that air bags are more effective in purely frontal than partially frontal crashes.

The data set for driver air bags in light trucks is less than a fourth the size of the set for passenger

cars. That increases sampling error in all the analyses, but especially in those based on driver vs.

right-front passenger fatalities, that have to be limited to vehicles in which both seats were occupied.

25
TABLE 2-2 - CAR DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 1841 1121

Purely frontal fatalities 1905 847 27

(statistically significant difference: x2 = 31.57)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 1841 1121

Partially frontal fatalities 1517 844

(not a statistically significant difference: x

2

 = 2.48)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 1841 1121

Frontal fatalities 3422 1691 19

(statistically significant difference: x2 = 18.83)

26
Table 2-3 shows a 19 percent fatality reduction in purely frontal crashes, but with cell counts of 52

driver and 72 right-front fatalities in the trucks equipped with air bags, this effect is not statistically

significant (x2 = 104). The other results in Table 2-3 - a 7 percent reduction in partially frontal

crashes, al l percent reduction in all frontal crashes, and al l percent increase in nonfrontal crashes -

likewise fall far short of statistical significance.

Table 2-4 compares frontal to nonfrontal driver fatalities in light trucks. Since these analyses can

include trucks in which the right-front seat was unoccupied, the cell counts are substantially larger.

The fatality reduction for driver air bags in purely frontal crashes is 35 percent, and it achieves

statistical significance at the .01 level (x2 = 13.46). The reduction in partially frontal crashes is 7

percent, and it is not statistically significant (x2 = 0.33). The combined effect in all frontal crashes

is a 23 percent fatality reduction, statistically significant at the .05 level (x2 = 6.37).

Tables 2-5 and 2-6 analyze the effectiveness of passenger air bags for car passengers age 13 or

older. As was noted in Section 1.7 and will be further discussed in Section 2.6, there is extensive

evidence from individual crash investigations that child passengers under age 13 can encounter unique

hazards in their interactions with air bags that make their experience quite different from the teen-age

and adult passenger population [14], [28]. Table 2-5 compares the fatality risk of right-front

passengers age 13 or older to drivers, in cars with dual and driver-only air bags. It is based on

substantially fewer data than the corresponding analyses for car drivers (Table 2-1), but more than

those for light truck drivers (Table 2-3). In purely frontal crashes, the observed fatality reduction for

passenger air bags, 24 percent, falls short of statistical significance (x2 = 2.67). Also positive, but

nonsignificant, are the observed effects in partially frontal crashes (11 percent reduction), in all frontal

crashes (18 percent) and in nonfrontal crashes (15 percent).

Table 2-6, based on a comparison of frontal to nonfrontal fatalities, yields results that are most

consistent with the pattern seen for car and light-truck drivers. In purely frontal crashes, passenger

air bags reduced the fatality risk of passengers age 13 or older by a statistically significant 30 percent

(X2 = 5.05, p < .05). In partially frontal crashes, the effect is a nonsignificant 5 percent. The

weighted average for all frontal crashes is an 18 percent reduction, falling short of statistical

significance (x2 = 2.42).

Table 2-7 summarizes all the fatality reduction estimates, and averages the estimates by the two

methods. The results, as presented in this table, show remarkable similarity in the effect of air bags

for car drivers, light truck drivers, and car passengers age 13 or older. For car driver air bags, the

fatality reduction in purely frontal impacts is statistically significant and close to 30 percent by each

method: the average is 30.5 percent. The effect in partially frontal impacts is nonsignificant by both

methods, and it averages out to a negligible 3.5 percent. The net effect in frontals averages to 18.5

percent, and the reduction is statistically significant by both methods.

The effects for driver air bags in light trucks, although based on far fewer data, average out to

essentially the same results as for car drivers: the fatality reduction averages 27 percent in pure

frontals, 7 percent in partial frontals, and 17 percent in all frontals. In the frontal vs. nonfrontal

analysis, the observed reductions in purely frontal and all frontal crashes are both statistically

significant.

27
TABLE 2-3 - LIGHT TRUCK DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

(both seats occupied; make-models that had manual 3-point belts

and added driver air bags without changing the belt system)

Driver Right Front Risk Percent

Fatalities Fatalities Ratio Reduction

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Trucks with belts only 164 183 .896

Trucks w. driver air bags 52 72 .722 19

(not a statistically significant difference: x

2 = 1 04)

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Trucks with belts only 153 140 1.093

Trucks w. driver air bags 76 75 1.013 7

(not a statistically significant difference: x

2 = 0.14)

IN ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Trucks with belts only 317 323 .981

Trucks w. driver air bags 128 147 .871 11

(not a statistically significant difference: x

2 = 0.69)

IN NONFRONTAL CRASHES

Trucks with belts only 156 184 .848

Trucks w. driver air bags 86 91 .945 -11

(not a statistically significant difference: x

2 = 0.34)

28
TABLE 2-4 - LIGHT TRUCK DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual 3-point belts and added driver air bags without changing the belt system;

excludes make-models that changed ABS status at the time they got air bags)

Trucks with Trucks with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 410 208

Purely frontal fatalities 574 188 35

(statistically significant difference: x2 = 13.46)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 410 208

Partially frontal fatalities 435 206

(not a statistically significant difference: %2 = 0.33)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 410 208

Frontal fatalities 1009 394 23

(statistically significant difference: %2~ 6-37)

29
TABLE 2-5 - CAR PASSENGERS AGE 13 OR OLDER, BY IMPACT LOCATION

EFFECTIVENESS OF PASSENGER AIR BAGS BASED ON REDUCTION OF

RIGHT FRONT PASSENGER FATALITIES RELATIVE TO DRIVER FATALITIES

(both seats occupied; make-models that had driver air bags with manual/automatic 3-point belts

and switched to dual air bags without changing the belt system)

Right Front Driver Risk Percent

Fatalities Fatalities Ratio Reduction

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Cars w. driver air bags 315 214 1.472

Cars w. dual air bags 109 97 1.124 24

(not a statistically significant difference. %2 = 2.67)

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars w. driver air bags 281 248 1.133

Cars w. dual air bags 146 144 1.014 II

(not a statistically significant difference: x

2

 = 0.58)

IN ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Cars w. driver air bags 596 462 1.290

Cars w. dual air bags 255 241 1.058 18

(not a statistically significant difference: %2 = 3.30)

IN NONFRONTAL CRASHES

Cars w. driver air bags 440 353 1.246

Cars w. dual air bags 237 225 1.053 15

(not a statistically significant difference: %2 = 2.06)

30
TABLE 2-6- CAR PASSENGERS AGE 13 OR OLDER, BY IMPACT LOCATION

EFFECTIVENESS OF PASSENGER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had driver air bags with manual/automatic 3-point belts

and switched to dual air bags without changing the belt system;

excluding make-models that got ABS at the same time as dual air bags)

Cars with Cars with Frontal Fat. Red.

Driver Air Bags Dual Air Bags for Passenger Bag (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 332 165

Purely frontal fatalities 236 82 30

(statistically significant difference: x2~ 5.05)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 332 165

Partially frontal fatalities 212 100

(not a statistically significant difference: x

2

 — 0.11)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 332 165

Frontal fatalities 448 182 18

(not a statistically significant difference: x

2 = 2.42)

31
TABLE 2-7: SUMMARY

FATALITY REDUCTION FOR AIR BAGS BY IMPACT LOCATION

Percent Fatality Reduction

Analysis Method

Compare

Driver to

Right Front*

Compare

Frontal to

Nonfrontal* Average

Driver air bags for cars

Purely frontal impacts

Partially frontal impacts

All frontal impacts

Nonfrontals

Driver air bags for light trucks

Purely frontal impacts

Partially frontal impacts

All frontal impacts

Nonfrontals

34

-2

18

- 4

19

7

11

-11

27

9

19

35

7

23

30.5

3.5

18.5

27

7

17

Passenger air bags for cars: passengers age 13 or older

Purely frontal impacts 24

Partially frontal impacts 11

All frontal impacts 18

Nonfrontals 15

30

5

18

27

8

18

* Statistically significant results are shown in bold italics.

32
Similarly, for car passengers age 13 or older, the fatality reduction for passenger air bags averages

to 27 percent in purely frontal crashes, 8 percent in partial frontals, and 18 percent in all frontals. In

short, air bags save lives for drivers and passengers age 13 or older, and most of their life-saving

benefit is in the purely frontal crashes, with a limited effect, at best, in the partially frontal crashes.

Approximate 90 percent confidence bounds (i.e., two-sided a = .05) for the fatality reductions in

purely frontal crashes may be developed from the entries in the top sections of Tables 2-2, 2-4 and

2-6, using the same method as in Section 1.5. The four numbers in the table, au, a12, a^ and a^, are

counts of fatalities in different vehicle types and crash modes, and they can be considered independent

Poisson variates. The effectiveness statistic in frontal crashes

E = 1-R = l-K^/aJ/C^/a,,)]

is based on a ratio of ratios, R, with approximate variance

V(R) « R2 [l/au + l/a12 + l/a^ + 1/aJ

In Table 2-2 (car drivers), where R = .73 and the table entries are 1841, 1121, 1905 and 847, the

standard deviation of effectiveness in frontal crashes is approximately

.73 [1/1841 + 1/1121 + 1/1905 + 1/847]

 5

 = .0409

Taking 1.645 standard deviations on either side of the "best" estimate of 30.5 percent yields

approximate confidence bounds:

.305 ± 1.645 x .0409 = 24 to 37 percent fatality reduction

for car drivers in purely frontal crashes. Similarly, the confidence bounds of fatality reduction by air

bags for light truck drivers in purely frontal crashes are 14 to 40 percent. The confidence bounds of

fatality reduction by passenger air bags for car passengers age 13 or older in purely frontal crashes

are 9 to 45 percent.

2.2 By car weight

The remaining analyses of this chapter, except for the discussion of child passengers in Section 2.6,

are all limited to driver air bags for cars, since there are not enough data to perform corresponding

analyses for car passengers or drivers of light trucks. One major question is whether the fatality

reduction for air bags varies with the size of the car. Specifically, the 1991 study by the Insurance

Institute for Highway Safety estimated a 36 percent overall fatality reduction for driver air bags in

large cars, but only 13 percent in mid-sized cars and 9 percent in small cars [29], pp. 8-9. Even

though the report did not assert that effectiveness was significantly higher in the large cars (which

it probably wasn't, given the limited data available at that time), it touched on an issue that was

already troubling researchers. Air bags might have a lower overall effect in small cars, they thought,

for several reasons: (1) There is less room and time to deploy the bags in a small car [13], p. III-7;

(2) A higher proportion of fatalities in small cars involve rollover or other circumstances where air

bags are less likely to be effective [5]. In particular, since many of the early air bag installations were

in large cars such as Mercedes, the early estimates of fatality reduction might be unrepresentative of

the "average" car on the road, and the estimates might decline over time as more and more small cars

became equipped with air bags.

Table 2-8 summarizes the fatality reductions for small, medium and large cars. The results in that

table are derived from more detailed analyses shown in Tables C-l - C-6 of Appendix C. "Small"

cars are defined here as those with curb weight of 2778 pounds or less, accounting for one-third of

33
TABLE 2-8

FATALITY REDUCTION FOR CAR DRIVER AIR BAGS

BY CAR SIZE AND IMPACT LOCATION

Percent Fatality Reduction

Analysis Method

Compare

Driver to

Right Front*

Compare

Frontal to

Nonfrontal* Average

Cars up to 2778 pounds

Purely frontal impacts

Partially frontal impacts

All crashes

Cars 2779-3119 pounds

Purely frontal impacts

Partially frontal impacts

All crashes

28

- 7

7

31

4

9

31

12

15

16

6

8

29.5

2.5

11

23.5

5

8.5

Cars over 3119 pounds

Purely frontal impacts

Partially frontal impacts

All crashes

43

- 1

13

34

3

13

38.5

1

13

* Statistically significant results are shown in bold italics.

34
the cars in the accident data. Curb weights are derived from R. L. Polk's National Vehicle

Population Profile [21], and they are averaged at the make-model level. Table 2-8 shows that the

fatality reduction for driver air bags in purely frontal crashes is close to 30 percent, by both analysis

methods, in small cars. Both reductions are statistically significant. The effect of air bags in partially

frontal crashes averages out to barely above zero, and it is not statistically significant. The fatality

reduction in all crashes averages to 11 percent, statistically significant in the frontal vs. nonfrontal

analysis method.

The fatality reductions for cars in the middle third of the weight distribution, 2779-3119 pounds, are

actually slightly lower, averaging 23.5 percent in purely frontal crashes, 5 percent in partially frontal

crashes, and 8.5 percent overall. The observed fatality reduction in purely frontal crashes averages

38.5 percent in the large cars (weighing over 3119 pounds), slightly higher than for small and

medium-sized cars. The average overall fatality reduction, 13 percent, is also slightly larger than in

small or mid-size cars.

These results suggest that air bags are about as effective in small cars as in larger cars. The pattern

and magnitudes of the fatality reductions are essentially the same in the three size groups. Although

the observed results for large cars are slightly better than for small and mid-sized cars, there is no

trend of increasing effectiveness as car size grows: the lowest observed reductions are generally in

the mid-sized cars.

The absence of a significant trend is confirmed by a C ATMOD analysis of the 3x2x 2 table

generated from the top sections of Tables C-4, C-5 and C-6 in Appendix C [27] - i.e., a tabulation

of purely frontal vs. nonfrontal driver fatalities, by car weight group and type of occupant protection

(driver air bag, no air bag); the car weight group is treated as a linear variable (2550, 3000 and 3450

pounds are the average weights in each group). Whereas the simple independent variable, "air bag"

has a strong association with the dependent variable (proportion of fatalities that are pure frontals),

as evidenced by x

2

 ~ 26.52, p < .01, the interaction term air bag x weight group does not have

significant association with the dependent variable (x2 = 0.08).

A possible caveat on the findings on car weight is that the analyses are perhaps biased in favor of

small cars, since they have, on the average, fewer old drivers. As will be shown in Section 2.5, air

bags are not as effective for old drivers as for young or middle-aged drivers. However, even when

these analyses are performed separately for drivers aged 14-55 and drivers over 55 years old, the

overall fatality reduction in both age groups is about the same in small cars as in large cars.

2.3 By vehicle manufacturer

Air bags may vary in design features, such as the type of sensors, deployment rate, deployment

threshold, etc. Conceivably, certain types of driver air bags might be substantially more effective than

others. The issue can be partially addressed by calculating the fatality reduction separately for four

groups of cars, each containing about a quarter of the accident cases: Chrysler Corp., Ford Motors,

General Motors, and imports (including transplants). Based on the method of comparing driver

fatalities to right-front passenger fatalities, and using the list of matching make-models and ranges

of model years from Table 1-1, the following fatality reductions are obtained:

35
Analysis of Matching Make-Models: Overall Fatality Reduction

Chrysler 10 percent

Ford

GM

Imports

8

13

3

In other words, the driver of a Chrysler car with an air bag had 10 percent lower fatality risk than the

driver of a Chrysler car not equipped with an air bag, etc. The differences in the preceding estimates

are well within the range of the sampling error that exists when the accident data are split four ways.

In fact, one of the problems with the analysis is the relatively small number of accident cases in each

cell. In comparisons of air bag effectiveness among subgroups of vehicles, it might be desirable to

increase the sample, even at the risk of some bias in the overall result. The numbers can be expanded

by including all model-year 1985-95 cars, not just the matching make-models and limited model years

specified in Table 1-1. While it was argued in Section 1.5 that expanding the data set to include many

model years could introduce vehicle-age biases into the results, the bias appears to minimal, at least

in the estimation of overall air bag effectiveness by the driver vs. right-front passenger analysis

method: the lower section of Table C-25 in Appendix C obtains an effectiveness estimate of 10

percent, for all manufacturers combined, with the larger data set; that is identical to the estimate in

Table 1-2 based on the matching make-models and limited model years. When effectiveness is

computed separately for each manufacturer with the larger data set, the results are:

Analysis of All Make-Models: Overall Fatality Reduction

Chrysler 11 percent

Ford 9

GM 10

Imports 9

These results strongly suggest that effectiveness is likely to be about the same in the four groups, and

they create no suspicion that the "differences" observed in the previous table are due to anything

other than sampling error.

2.4 Single vs. multivehicle crashes

Frontal single-vehicle crashes frequently involve conditions quite different from the flat-barrier crash

tested in FMVSS 208. For example, the object contacted, such as a tree or pole, is often narrow, and

the resulting damage pattern may include significant intrusion of structures into the occupant

compartment; the off-road excursion prior to impact may throw occupants out of position. That

raises a possible concern that air bags could be less effective in single-vehicle than in multivehicle

crashes.

Table 2-9 compares the fatality reduction for driver air bags in single-vehicle and multivehicle crashes

(detailed analyses may be found in Tables C-7 - C-10 of Appendix C). The analysis based on

36
TABLE 2-9

FATALITY REDUCTION FOR CAR DRIVER AIR BAGS

BY CRASH TYPE AND IMPACT LOCATION

Percent Fatality Reduction

Analysis Method

Single-vehicle crashes

Purely frontal impacts

Partially frontal impacts

All crashes

Multivehicle crashes

Purely frontal impacts

Partially frontal impacts

All crashes

Compare

Driver to

Right Front*

22

-6

4

39

4

14

Compare

Frontal to

Nonfrontal*

26

12

12

26

6

12

Average

24

3

8

32.5

5

13

*Statistically significant results are shown in bold italics.

37
comparison of drivers to right-front passengers produces more favorable results in the multivehicle

crashes, whereas the frontal vs. nonfrontal analysis yields nearly identical effectiveness in single- and

multivehicle crashes. That method yields four statistically significant reductions: in purely frontal

single-vehicle crashes, in all single-vehicle crashes, in purely frontal multivehicle crashes and in all

multivehicle crashes. When the estimates from the two methods are averaged, the fatality reduction

in single-vehicle and multivehicle crashes is essentially the same (within sampling error), perhaps

leaning toward a slightly better performance in the multivehicle crashes. For example, the fatality

reduction is 24 percent in purely frontal single-vehicle crashes and 32.5 percent in multivehicle. The

overall fatality reduction is 8 percent in single and 13 percent in multivehicle crashes.

2.5 By occupant age and sex

Intrinsic vulnerability to fatal injury, given exposure to the same crash forces, increases by 2-5 percent

for each year that an adult occupant gets older, and it is 30 percent higher for females than for males

[8], pp. 22-28; [18], p. 9. Given the substantial differences in occupant responses to impact, it is

appropriate to investigate any crashworthiness measure to see if the fatality reduction varies with

occupant age and sex. It is especially appropriate with driver air bags, since older drivers and women,

if they are of short stature, may sit close to the steering wheel and be in a position to interact with the

air bag during its forceful early stages of deployment.

The analysis method that compares fatalities in frontal to nonfrontal crashes may be applied, without

change from the procedures in the preceding sections, to any subset of drivers, such as drivers in a

particular age group, or male drivers. It is not so simple with the analysis method that compares

driver to right-front passenger fatalities. If we want, for example, to calculate fatality reduction for

14-29 year old drivers, is it permissible to include all cases where a 14-29 year old driver was a

accompanied by a right-front passenger of any age, or is it better to limit the analysis to cases where

the driver and the passenger were both 14-29 years old? Theoretically, both approaches are valid

applications of "double-pair comparison analysis [7]," but, somehow, the latter approach is

preferable: the benefit of driver air bags is most easily interpreted if the baseline crashes are those

where the driver and passenger are about the same age, and thus about equally at risk.

Table 2-10 summarizes all the analyses of fatality reduction by driver age group. Three large age

groups were initially considered: 14-29, 30-55 and 56+. The results for 14-29 and 30-55 are about

the same, as will be described below, but the 56+ group shows a drop in effectiveness, suggesting

additional study. That group is subdivided into ages 56-69 and 70+, and fatality reduction is

calculated separately for those subgroups. The detailed analyses supporting Table 2-10 are Tables

C-ll - C-20 of Appendix C.

In purely frontal crashes with a 14-29 year old driver and passenger, air bags reduce the driver's

fatality risk by a statistically significant 37 percent (see also Table C-ll). In partially frontal crashes,

the reduction is a nonsignificant 3 percent. The overall reduction for 14-29 year old drivers, by this

method, is a nonsignificant 14 percent. The method of comparing frontal to nonfrontal crashes yields

statistically significant reductions for 14-29 year olds (see also Table C-13) in purely frontal and in

all frontal crashes. The average for the two methods is a 32 percent fatality reduction in purely

frontal impacts, 8 percent in partial frontals, and an average of 13.5 percent in all crashes.

38
TABLE 2-10. FATALITY REDUCTION FOR CAR DRIVER AIR BAGS

BY DRIVER AGE AND IMPACT LOCATION

Percent Fatality Reduction

Analysis Method

Age 14-29

Purely frontal impacts

Partially frontal impacts

All crashes

Age 30-55

Purely frontal impacts

Partially frontal impacts

All crashes

Age 56 or older

Purely frontal impacts

Partially frontal impacts

All crashes

Age 56-69

Purely frontal impacts

Partially frontal impacts

All crashes

Age 70 or older

Purely frontal impacts

Partially frontal impacts

All crashes

Compare

Driver to

Right

Front*

37

3

14

31

-11

10

Compare Frontal to Nonfrontal

Matching

Make-Models*

27

13

13

35

13

17

17

- 10

4

23

- 8

8

11

- 1 1

2

All Make-Models

(Adjusted)

27

6

12

11

- 5

1

Averag

32

8

13.5

35

13

17

24

- 10.5

7

25

- 1

10

11

- 8

1.5

"Statistically significant results are shown in bold italics.

39
There are not enough accident cases with a 30-55 year old driver and right-front passenger for a

statistically meaningful analysis; thus only the frontal vs. nonfrontal analysis is used for that age

group. The observed fatality reductions are statistically significant, and even slightly higher than the

corresponding values for 14-29 year olds (see also Table C-14), reaching 35 percent in purely frontal

crashes.

The first two sections of Table 2-10, comprising drivers up to 55 years old, show consistent benefits

for air bags: a reduction of 30 percent or more in purely frontal crashes, nonsignificant but

consistently positive observed effects in partially frontal crashes, and an overall effect well above the

11 percent average in Chapter 1.

Mixed results are obtained for drivers age 56 or older, as shown in the third section of Table 2-10.

When the analysis is based on comparing drivers age 56+ to right-front passengers age 56+ (see also

Table C-12), the reduction in purely frontal crashes is a statistically significant 31 percent. It is partly

offset, however, by a nonsignificant 11 percent fatality increase in partially frontal crashes. The net

effect is a 10 percent reduction. The frontal vs. nonfrontal analysis (Table C-15), based on more than

twice as many accident cases, yields less favorable results: a nonsignificant 17 percent reduction in

purely frontal impacts, a nonsignificant 10 percent increase in partial frontals, and a net reduction of

just 4 percent.

If the fatality reduction for air bags drops off after age 55, it is appropriate to ask if the results get

worse as the drivers get older. The last two sections of Table 2-10 consider 56-69 and 70+ year old

drivers separately. In these subgroups, there are not enough cases for a meaningful driver vs. rightfront passenger analysis, and even the frontal vs. nonfrontal analysis is based on somewhat sparse

data, with cell counts sometimes well under 200 (see Tables C-16 and C-17). That analysis is

supplemented by another method that permits the use of additional data, although it needs correction

for biases.

As explained in Section 1.5, the frontal vs. nonfrontal method was limited to selected make-models

equipped with air bags for which there existed matching data of the same make-models without air

bags. No more than 3 model years before or after the switch to air bags were included. Any model

that got Antilock Brake Systems (ABS) at about the same time as air bags was excluded, since ABS

also shifts the fatal-accident distribution to a lower proportion of frontals [16], [20]. If the accident

data set is expanded to include all 1985-95 cars (except those with 2-point automatic belts), for all

model years, regardless of ABS status, the number of cases with air bags doubles, and the number

without air bags increases by a factor often. Table C-18 computes the fatality "reduction" for air

bags with this expanded data set for drivers of all age groups, to investigate the extent of bias in the

results. Fatality "reduction" in purely frontal crashes is 33 percent, which is 6 percent above the value

in the unbiased frontal-nonfrontal analysis with matching makes and models (Table 2-2). The

reduction in partial frontals is 10 percent, 1 percent beyond the unbiased value. The reduction in all

frontals is 24 percent, 5 percent above the unbiased value. Fatality reduction in all crashes is 16

percent, 4 percent above the unbiased value in Table 1-3. These observed biases (6, 1, 5 and 4

percent, respectively) are subtracted from the results obtained for any subset of this expanded data

set to adjust those results and make them comparable to the unbiased estimates.

40
Thus, for example, in the limited data set with matching make-models, the fatality reduction for air

bags for 56-69 year old drivers in purely frontal crashes is 23 percent (see also Table C-16). After

adjustment for bias (i.e., subtraction of 6 percent; see Table C-19), the fatality reduction in the

expanded data set is 27 percent. The average of the two estimates is 25 percent. There is a 1 percent

increase in the partially frontal crashes. The overall fatality reduction averages 10 percent. All of

these numbers are still close to the average for drivers of all ages, combined.

The results are less favorable for drivers age 70 or older. The fatality reduction in purely frontal

crashes is 11 percent in both data sets. The effect in partially frontal crashes is consistently negative,

although not statistically significant. The effect in all crashes is a nonsignificant 2 percent in the

limited data set and 1 percent in the expanded set, averaging out to 1.5 percent.

These data, at first glance, suggest that air bags have little net benefit for older drivers. An important

caveat, however, is that the results on older drivers are based on relatively small samples and are less

precise than the estimates for young drivers. Whereas the "best" estimate of overall fatality reduction

for drivers age 70 or older is 1.5 percent, the confidence bounds for effectiveness range from -12 to

+15 percent. (These confidence bounds are calculated by the same method as in Section 1.5 - i.e.,

90 percent confidence bounds.) Thus, while the central tendency in the data suggests that the effect

is close to zero, it is possible that air bags could be as beneficial for old as young drivers (but it is also

conceivable that air bags could have a negative effect for old drivers.)

Is it possible, at least, to infer that air bags are significantly less effective for drivers age 70 or older

than for drivers age 55 or younger? CATMOD analyses of 2 x 2 x 2 tabulations of fatalities by crash

mode (e.g., purely frontal vs. nonfrontal; or, alternatively, any frontal vs. nonfrontal), driver age (up

to 55, 70 or older) and type of occupant protection (driver air bag, no air bag) produce mixed results.

With the limited data set of matching make-models, the interaction term air bag x age group falls

short of statistical significance (x2 = 2.35) when the dependent variable is the proportion of fatalities

that are pure frontals. The interaction term also falls short of significance (x2 = 2.69) when the

dependent variable is the proportion of fatalities that are purely or partially frontal. However, with

the extended data set including all make-models in all model years, 1985-95, both of these interaction

terms become statistically significant at the .01 level: x

2 = 1001 in the analysis of pure frontals and

X

2

 = 8.45 in the analysis of all frontals. In other words, with this data set, air bags are significantly

less effective for drivers age 70 or older than for drivers age 55 or younger. (Whereas the extended

data set produces biased effectiveness estimates, it is not unreasonable to assume that the biases will

be about the same for various subgroups of the driver population, and to use this data set, without

adjustments, for testing the interaction between driver age and air bag effectiveness.)

If air bags have little net benefit for older drivers, it does not necessarily imply that they have no

effect at all. It is entirely possible that they do good in some crashes and harm in others, and the harm

cancels out the good. Actually, there are three possible ways that air bags could have a zero net

effect for older drivers:

(1) All of the fatal lesions for these drivers involve components other than the air bag, such as the

A-pillar, header, belt system, noncontact injury, etc. Air bags are irrelevant to these injuries.

The people are dying from the same injury sources as they did without air bags.

41
(2) Some people are dying from lesions involving interaction with the air bag. However, these

same people would have died from contacts with other components, such as the steering

assembly, if an air bag had not been there. Air bags are causing some fatal lesions, but only

to people who would not have survived anyway.

(3) Air bags are causing fatal injuries to some drivers who would have survived the same crash

if the car had not been equipped with air bags. But they are also saving the lives of some

other drivers who would have died if the car had not been equipped with air bags. The

number of new fatalities is equal to the number of lives saved, resulting in a zero net effect.

The FARS data do not provide any information on the injury sources of occupants. Nevertheless,

our experience with crash testing and in-depth accident investigation suggest that (1) is the least likely

possibility. Similarly, the consistently positive findings in pure frontal crashes and negative in partially

frontal crashes, although nonsignificant, also lean in the direction that air bags sometimes do good

and sometimes do harm to older drivers. If either (2) or (3) is correct, it would imply that current

air bags sometimes apply forces that cannot be endured by older drivers.

Given that air bags are less effective for older drivers, one might also expect a lower fatality reduction

for female drivers. Table 2-11 (derived from detailed Tables C-21 - C-24 in Appendix C) compares

fatality reductions by air bags for male and female drivers. The driver vs. right-front passenger

analysis method is not used, since there not so many accident cases in which the driver and passenger

are of the same gender. Instead, the frontal vs. nonfrontal analysis is applied in two versions, with

the limited list of matching make-models; and with all 1985-95 cars, corrected for bias due to ABS,

etc. In the matching make-models, the fatality reduction for air bags in purely frontal crashes is

statistically significant for both male and female drivers. However, the reduction is slightly, but

consistently higher for males than females in every impact type: 28 vs. 25 percent in pure frontals, 12

vs. 2 percent in partial frontals, and 14 vs. 9 percent overall. In the larger data set, after correction

for bias, the results are essentially similar, except the observed difference between males and females

is smaller in purely frontal crashes, and overall: e.g., 13 vs. 10 percent overall effectiveness. These

data could support a hypothesis that air bags are somewhat less effective for women than men, but

they are also compatible with the hypothesis that fatality reduction is about equal for men and women:

specifically, CATMOD analyses of 2 x 2 x 2 tabulations of fatalities in the limited data set by crash

mode, driver's gender and type of occupant protection did not show a statistically significant

interaction between gender and air bag effectiveness in purely frontal crashes (x2 =0.12) or in all

types of frontal crashes (x2 = 0.50).

A final question is whether the combination of age and gender affects fatality reduction, viz., if female

drivers age 70 or older, who may combine high vulnerability to impact with short stature, are

experiencing problems with air bags. The current data do not reveal this to be the case. In frontal

vs. nonfrontal analyses, the results for female drivers age 70 or older are nearly identical to those for

males over 70. Neither group, however, experienced a statistically significant fatality reduction; both

had overall effects close to zero.

42
TABLE 2-11

FATALITY REDUCTION FOR CAR DRIVER AIR BAGS

BY DRIVER'S GENDER AND IMPACT LOCATION

Percent Fatality Reduction

Analysis Method:

Compare Frontal to Nonfrontal

Male drivers

Purely frontal impacts

Partially frontal impacts

All crashes

Female drivers

Purely frontal impacts

Partially frontal impacts

All crashes

Matching

Make-Models*

28

12

14

25

2

9

All Make-Models

(Adjusted)

28

13

13

27

5

10

Average

28

12.5

13.5

26

3.5

9.5

*Statistically significant results are shown in bold italics.

43
2.6 Passenger air bags and children

Recent in-depth investigations of crashes involving fatalities of child passengers in vehicles equipped

with dual air bags revealed a substantial number of cases in which the fatal lesions appear to have

involved interaction of the child, or a rear-facing child safety seat, with the passenger air bag: a

NHTSA press release cited 19 such cases cumulative through May 1996 [28], while an article in USA

Today, listed 22 cases cumulative through early July 1996 [14]. Fourteen of the crashes occurred

before the end of 1995, and the remainder in calendar year 1996. The principal concern raised by the

in-depth investigations as well as earlier crash tests and engineering analyses is that children are

shorter and lighter than adults. That makes unbelted or incorrectly belted children prone to being

tossed forward during panic braking or minor impacts prior to the deployment of the air bag. Some

children, even correctly belted ones, may sit far forward in their seat (e.g., to look out the window

or adjust the radio), close to the air bag, during normal vehicle operations. A parallel concern is that

rear-facing child safety seats place infants close to the air bag when they are placed in the right-front

seat of a vehicle. Either way, the child's head, neck and thorax can be in the path of the deploying

air bag during the forceful early stages of the deployment. An additional worry is that the youngest

children are intrinsically more vulnerable to injury than teenagers or young adults.

It is appropriate to perform statistical analyses of the limited available FARS data involving vehicles

with dual air bags that had children occupying the right-front seat. The objective of the statistical

analyses is not to find out if children are experiencing problems with current air bags: the in-depth

accident investigations have already established that they do. All the statistical analyses can add is

quantitative information about the risk of children in cars equipped with dual air bags relative to the

risk of children in cars without air bags; the analyses may be helpful in identifying groups of crashes

where fatality risk with air bags is higher than expected. The FARS data in this analysis are complete

only through early 1996 and exclude the most recent child passenger fatalities that have been

investigated by NHTSA. On the other hand, the FARS data are not limited to cases of children who

received fatal lesions from contacts with air bags; the 38 FARS records of child passenger fatalities,

age 0-12, who had been occupying the right-front seat of a car equipped with dual air bags includes

children who received fatal injuries from sources unrelated to air bags - e.g., in nonfrontal crashes.

The statistical analysis addresses these questions, to the extent possible given the available data:

(1) Do children in the right-front seat have a higher fatality risk with dual air bags?

(2) At what ages is there an increase in fatality risk?

(3) In what types of crashes does fatality risk increase?

(4) How large is the increase? Is it statistically significant?

Table 2-12 addresses the first two questions. It computes the overall fatality reduction by passenger

air bags for all right-front passengers from infants up to the age shown in the stub column, based on

comparisons of right-front and driver fatalities in crashes of cars with dual air bags, and cars with

driver air-bags only. Drivers of all ages are included in the analyses. The data are not limited to the

make-models and model-year ranges of Table 1-7, but compare all cars with dual air bags and 3-point

[manual or automatic] belts to all cars with driver air bags and 3-point belts. The extended data set

is used to maximize the number of accident cases in the analysis; extending the data set may introduce

biases on the order of 5 percent, as discussed above, but such biases are trivial in the context of the

44
TABLE 2-12 - CAR PASSENGERS, BY AGE OF THE CHILD PASSENGER:

EFFECTIVENESS OF PASSENGER AIR BAGS BASED ON REDUCTION OF

RIGHT FRONT PASSENGER FATALITIES RELATIVE TO DRIVER FATALITIES

(both seats occupied; all cars with driver or dual air bags and 3-point belts)

Cumulative Occupant Fatality Counts

Passenger

Age Group

0

0-1

0-2

0-3

0-4

0-5

0-6

0-7

0-8

0-9

0-10

0-11

0-12

0-13

0-14

0-15

All ages

Cars with

Dual Air Bags

Rt Front Drivers

A B

4

• 6

8

9

17

23

29

31

32

33

34

35

38

40

45

52

759

1

2

3

3

10

12

15

20

22

23

24

28

30

34

50

66

721

Cars with

Driver Air Bags

Rt Front Drivers

C D

7

11

17

26

30

36

40

44

48

52

54

59

74

86

109

153

2198

7

11

19

26

30

42

52

59

70

78

88

96

110

126

142

189

1843

Cumulative

% Reduction

for Passenger

Air Bags

(1 - AD/BC) %

-300

-200

- 198

-200

-70

-124

- 151

- 108

- 112

-115

-131

-103

-88

-72

-17

3

12

45
large effects for air bags shown in Table 2-12.

In the cars with dual air bags, Table 2-12 shows that, cumulative up to age 13, the number of child

passenger fatalities exceeds the fatalities among the drivers who accompanied those passengers. For

example, there were 34 fatalities to children age 0-10 (column A) and only 24 of the drivers

accompanying them were fatally injured (column B). But in the cars with a driver air bag and no

passenger bag, child passenger fatalities (C) initially are about the same as driver fatalities (D), and

with the inclusion of children age 8-13, who are at substantially lower risk than adults, C gets steadily

smaller than D - e.g., 54 passenger fatalities age 0-10 and 88 deaths among the drivers of those cars.

Thus, the observed fatality reduction for passenger air bags is consistently negative for child

passengers. Moreover, after the fluctuation in the first few years, as might be expected with the small

numbers of accident cases, the effect settles down to about a 120 percent increase and stays there up

through age 10. When the 11-13-year-olds are added to the data, the results gradually turn in a more

favorable direction for air bags. The inclusion of 14-year-olds dramatically improves the results for

air bags, and the inclusion of 15-year olds makes the results cross over to a net benefit. Finally, when

right-front passengers of all ages are included in the analysis, the net fatality reduction for passenger

bags is 12 percent. The table shows that right-front passengers age 16 or older are far more

numerous than child passengers; as a consequence, the positive results for adult and teenage

passengers statistically eclipse the negative effects for child passengers.

Thus, Table 2-12 shows that the fatality increase with passenger air bags persists from birth up

through age 10. Positive results for air bags appear to begin in the 11-13 age range and become quite

strong at ages 14 and 15. Of course, given the small number of accident cases, Table 2-12 cannot

be expected to provide definitive answers on what age children experience increased fatality risk with

air bags, but the numbers appear to be consistent withNHTSA's position that problems might persist

up through age 12. At age 13, a large proportion of teenagers are as tall or taller than a small adult

female, and they have legs long enough to contact the instrument panel or firewall and prevent the

head and torso from being thrown too far forward during pre-crash braking. At age 11 and 12, some

children are already as tall as small adults, but many are not. Up to age 10, most children are shorter

than a small adult female, and they are at risk of being thrown forward prior to air bag deployment,

or they may be sitting far forward in the seat even during normal vehicle operations.

Table 2-13 helps to explain what types of crashes result in higher fatality risk for children with

passenger air bags. Fatality reduction is calculated for child passengers age 0-12 by the driver vs.

right-front method for various subsets of the data used in Table 2-12. The first section of Table 2-13

recapitulates the "0-12" row of Table 2-12, and shows an 88 percent fatality increase for passenger

air bags that is statistically significant at the .05 level (x2 = 4.93).

When the analysis is limited to frontal and partially frontal crashes, the negative effect gets stronger:

a 112 percent increase. When it is further limited to purely frontal crashes, the effect escalates to a

186 percent increase. Finally, when the data are further limited to purely frontal impacts with

another vehicle, the increase grows to 236 percent. Each of these three increases is statistically

significant at the .05 level (x2 = 4.30, 5.07 and 5.03, respectively). It is noteworthy that 16 of the

38 child passenger fatalities with air bags are in purely frontal multivehicle impacts, but just 17 of 74

fatalities without the air bags. Again, this result makes intuitive sense. Multivehicle crashes, unlike

46
TABLE 2-13 - CHILD PASSENGERS AGE 0-12, BY IMPACT LOCATION:

EFFECTIVENESS OF PASSENGER AIR BAGS BASED ON REDUCTION OF

RIGHT FRONT PASSENGER FATALITIES RELATIVE TO DRIVER FATALITIES

(both seats occupied; all cars with driver or dual air bags and 3-point belts)

Right Front Driver Risk Percent

Child Fatalities Fatalities Ratio Reduction

IN ALL CRASHES

Cars w. driver air bags 74 110 .672

Cars w. dual air bags 38 30 1.267 -88

(statistically significant difference: x2 - 4.93)

IN ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Cars w. driver air bags 43 63 .683

Cars w. dual air bags 26 18 1.444 -112

(statistically significant difference: X2 = 4.30)

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Cars w. driver air bags 20 35 .571

Cars w. dual air bags 18 11 1.636 -186

(statistically significant difference: x2 - 5.07)

IN PURELY FRONTAL MULTIVEHICLE CRASHES

(12:00 principal impact; most harmful event is not a rollover; 2 or more vehicles in the crash)

Cars w. driver air bags 17 25 .680

Cars w. dual air bags 16 7 2.286 -236

(statistically significant difference: x2 = 5.03)

47
run-ofiF-road fixed-object impacts, are likely to involve a reasonably alert driver who may slam on the

brakes in a final attempt to avoid hitting the other vehicle. In a purely frontal impact, that could result

in the child being thrown toward the air bag just before it deploys.

For a "best estimate" of the actual effect of passenger air bags and an assessment of its statistical

significance, the analysis method of Table 2-14 is recommended for use with the current, rather sparse

accident data. One problem with Tables 2-12 and 2-13 is that the "control group" data set of child

passengers in cars with driver air bags is itself rather small, and it may be contributing to the sampling

error. A much larger data set of child passengers may be obtained by considering 1985-95 cars with

3-point belts and no air bags at all. The first section of Table 2-14 shows that these 0-12 year old

right-front passengers have experienced 1046 fatalities to date, while 1184 of the accompanying

drivers were killed in crashes. Since those drivers were not protected by air bags, they are not

directly comparable to the drivers in the cars with dual air bags. However, a principal finding of

Chapter 1 was that driver air bags reduce fatality risk by 11 percent. Thus, if those cars had been

equipped with driver air bags, the 1184 driver fatalities would have decreased by 11 percent, to 1054,

and there still would have been the same 1046 child passenger fatalities, a risk ratio of .992 for the

children. In the cars with dual air bags, the risk ratio was 1.267. The estimated fatality reduction for

passenger bags is -28 percent, and it is not statistically significant (x2 = 0.97).

Similarly, in purely frontal multivehicle crashes, there were 268 child passenger fatalities and 364

driver fatalities in the cars without air bags. If these cars had been equipped with driver air bags, we

may assume the driver fatalities would have decreased by 30 percent, to 255 (see Table 2-7). The

risk ratio for child passengers is 1.051 without air bags and 2.286 with air bags. The estimated

fatality reduction is -117 percent, and it falls short of statistical significance (x2 = 2.96).

In other words, the best estimate with the currently available data is that child passenger fatalities

could be increasing with air bags, substantially so in purely frontal crashes. The findings by the

preferred analysis method are not statistically significant (Table 2-14), although the findings by

another method are statistically significant at the .05 level (Table 2-13). These statistical analyses,

in the absence of evidence from any other source, would ordinarily not be sufficient to conclude

definitively that child passenger fatalities are increasing with air bags, let alone to determine a specific

numerical value for the increase. However, in this case, there is already substantial evidence from indepth accident investigations that child passengers can have fatal interactions with air bags, and the

statistical findings of this report are consistent with the concerns raised by the in-depth investigations.

At this time, the fleet of vehicles equipped with passenger bags is expanding rapidly, and the analyses

shown here can and should be updated with extensive new data during the next 12 months.

In summary, in-depth investigations revealed 14 cases during 1986-95 in which fatal lesions appear

to have involved interaction of a child, or a rear-facing child safety seat, with the passenger air bag.

It was estimated in Section 1.8 that passenger air bags saved the lives of 88 passengers age 13 or

older during that time period. The number of lives saved far exceeded the child passenger fatalities

primarily because the overwhelming majority of right front passengers, even during 1986-95, were

adults or teenagers, not children. The Department of Transportation and other organizations are now

striving to inform all parents that the safest place for children is the back seat. Parents can generally

eliminate the air bag risk by insisting that their children ride buckled up in the back seat.

48
TABLE 2-14 - CHILD PASSENGERS AGE 0-12, BEST ESTIMATES

EFFECTIVENESS OF PASSENGER AIR BAGS BASED ON REDUCTION OF

RIGHT FRONT PASSENGER FATALITIES RELATIVE TO DRIVER FATALITIES

CARS WITH DUAL AIR BAGS VS. CARS WITH NO AIR BAGS

(both seats occupied; all cars with dual air bags and 3-point belts vs. cars with 3-point belts only)

Right Front Driver Risk Percent

Child Fatalities Fatalities Ratio Reduction

IN ALL CRASHES

1184 *

Cars with belts only 1046 1054 § .992

Cars w. dual air bags 38 30 1.267 -28

(not a statistically significant difference: %2 = 0.97)

IN PURELY FRONTAL MULTIVEHICLE CRASHES

(12:00 principal impact; most harmful event is not a rollover; 2 or more vehicles in the crash)

364 *

Cars with belts only 268 255 % 1.051

Cars w. dual air bags 16 7 2.286 -117

(not a statistically significant difference: %2 = 2.96)

* Actual fatalities

§ Fatalities diminished by 11 percent to simulate risk with driver air bags

t Fatalities diminished by 30 percent to simulate risk with driver air bags

49

CHAPTER 3

AIR BAG EFFECTIVENESS FOR BELTED VS. UNRESTRAINED CAR DRIVERS

3.1 What does it matter?

The overall "as used" fatality reduction by air bags for all drivers of passenger cars - belted and

unrestrained drivers combined - is approximately 11 percent. Thus, the two "when used" fatality

reductions, as defined in Section 1.4 - (1) air bag effectiveness for the unrestrained driver, and (2) air

bag effectiveness for the belted driver (i.e., the incremental effectiveness of an air bag plus belts over

just wearing the belts) - have to "average" out to 11 percent. However, there are many combinations

that could average to that number. For example, if both "when used" reductions were exactly 11

percent, they would of course average to 11 percent. But it is also conceivable that one of the

reductions is much higher than 11 percent while the other is zero or even negative - and they average

out to 11 percent. Why are we interested in the two "when used" reductions if, no matter what they

are, we already know they will average to 11 percent? Three important reasons come to mind.

First, the "when used" reductions can resolve whether 11 percent is a stable or unstable measure of

overall fatality reduction. If incremental air bag effectiveness is about the same for the belted and the

unrestrained driver, the 11 percent overall effect will stay about the same in the future, even if belt

use were to change a lot. But if, for example, air bags were only effective for the unrestrained

occupant, and belt use were to increase to over 90 percent, the overall benefits of air bags would

dwindle, and the 11 percent estimate, although valid today, would have little meaning in the future.

Second, a policy issue is at stake. If the accident data were to show, for example, that air bags only

benefitted unbelted occupants, and that they did not benefit, or in some cases even harmed belt users,

the majority of the population that buckles up might question the need and expense of air bags. (A

few years ago, a similar issue was raised with some automatic belts that were perceived as offering

less protection for more money to people who already used manual belts.) On the other hand, if the

accident data show that air bags have significant benefits for belted and unrestrained drivers, the issue

becomes moot.

Third, any knowledge about the effectiveness of air bags for specific subgroups of the population -

belt users and nonusers - would be helpful for engineers developing more effective systems.

The analysis would be straightforward if it were possible to rely entirely on the accuracy of belt use

reporting in fatal crashes. In that case, it would be possible to do separate analyses of fatality

reduction by air bags for the belted and the unbelted occupants, just like the analyses in Chapter 2 for

old vs. young drivers, males vs. females, etc. However, the consensus is that FARS does not

necessarily contain accurate information about the belt use of crash survivors, especially in recent

years [24]. Basically, police who investigate fatal crashes are usually not eye-witnesses to the crash

itself They arrive several minutes later, at which point survivors may be out of the car. Police may

have to rely on the survivor's statement of belt use when no other evidence is available; survivors do

not necessarily wish to report that they were unrestrained, especially if belt use is required by law.

51
It is widely assumed that FARS reports belt use quite accurately for fatalities, who may not have been

moved between the crash and the arrival of the police. However, even for fatalities, evidence of belt

use is not always directly observable several minutes after the crash, and there are factors that make

it hard to ascertain belt use accurately, or that could bias its reporting. Thus, the less the data analysis

relies on belt use reporting in FARS, especially for survivors, and the more it relies on directly

observable phenomena, the less uncertainty there might be in the results. Three methods for analyzing

the data are used here: the first relies directly on FARS belt use reporting for fatalities and survivors,

the second on fatalities only, and the third not directly on either.

3.2 Estimates based on FARS-reported belt use

Notwithstanding the caveats about belt use reporting on FARS, it's at least worth the effort to see

what happens when fatality reduction for air bags is calculated for belt users and nonusers - as

reported in FARS. The analysis method is the comparison of driver and right-front passenger

fatalities in the cars, as defined in Section 1.5. However, not all available accident cases will be

included: we will analyze only the cars in which the driver and right-front passenger were both belted

according to FARS (to estimate fatality reduction by air bags for belted drivers) or in which they were

both unbelted (to estimate the reduction for unrestrained drivers). There are two reasons for

choosing only the cases where the control group (right-front passengers) has the same belt use as the

drivers. (1) As in the analyses of effectiveness by occupant age (Section 2.5), the benefit of air bags

is most easily interpreted if the baseline crashes (in cars without air bags) are those where the driver

and passenger have the same belt use, and thus about equally at risk. (2) There may be intuitive

reasons to believe that when FARS reports both people as belted, or both as unbelted, it's more likely

to be accurate than when it reports one occupant as belted (the survivor in almost all cases) and the

other as unbelted (the fatality in almost all cases), and there is a suspicion that the report of belt use

or nonuse could have been influenced by the outcome of the crash.

Table 3-1 estimates the fatality reduction for driver air bags in crashes where both front-seat

occupants were belted according to FARS (RESTJUSE or MAN_REST = 1, 2, 3, 8, or 13). The

analysis is limited to the make-models, and model year ranges listed in Table 1-1. In the cars without

air bags, there were 264 driver fatalities and 308 right-front passenger fatalities in purely frontal

crashes, a risk ratio of .857. In other words, a belted driver is slightly less at risk than a belted

passenger. But with driver air bags, there were only 130 driver fatalities (with air bag and belts) vs.

197 right-front passenger fatalities (with belts only), a risk factor of .660. That is a 23 percent fatality

reduction by air bags for belted drivers, and it falls short of statistical significance (x2 = 3.46). Table

3-1 also shows close to a zero effect for air bags in partially frontal crashes. In all crashes, the fatality

reduction is 5 percent, and it is not statistically significant (x2 = 0.39).

In an effort to include more accident cases, Table 3-1X extends the analysis to a comparison of all

model year 1985-95 cars with driver air bags and 3-point belts vs. all 1985-95 cars with 3-point belts

only - i.e., not just the makes, models and model years in Table 1-1. That increases the sample of cars

with air bags by about 40 percent and cars with belts only by a factor of 5. Fatality reductions stay

about the same: the reduction in purely frontal crashes is 21 percent, and, with this larger sample, the

reduction is statistically significant at the .05 level (x2 = 5.64). The effect in partially frontal crashes

is again close to zero, and the overall reduction is a nonsignificant 7 percent. (Unlike the frontal vs.

52
TABLE 3-1 - BELTED DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

DRIVER AND RIGHT-FRONT SEATS BOTH OCCUPIED BY

PEOPLE WEARING BELTS ACCORDING TO FARS

LIMITED DATA SET: MAKE-MODELS THAT HAD MANUAL OR AUTOMATIC 3-POINT BELTS

AND ADDED DRIVER AIR BAGS WITHOUT CHANGING THE BELT SYSTEM

Driver

Fatalities

Right Front

Fatalities

Risk

Ratio

Percent

Reduction

Cars with belts only

Cars w. driver air bags

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

264 308 .857

130 197 .660

(not a statistically significant difference: x

2 = 3.46)

23

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only

Cars w. driver air bags

216 232 .931

137 146 .938

(not a statistically significant difference: x

2 = 0.03)

-1

Cars with belts only

Cars w. driver air bags

IN ALL CRASHES

844 1001 .843

509 633 .804

(not a statistically significant difference: %2 = 0.39)

53
TABLE 3-1X - BELTED DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

DRIVER AND RIGHT-FRONT SEATS BOTH OCCUPIED BY

PEOPLE WEARING BELTS ACCORDING TO FARS

EXTENDED DATA SET: ALL 1985-95 CARS WITH DRIVER AIR BAGS AND 3-POINT BELTS

VS. ALL 1985-95 CARS WITH 3-POINT BELTS ONLY

Driver

Fatalities

Right Front

Fatalities

Risk

Ratio

Percent

Reduction

Cars with belts only

Cars w. driver air bags

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

1505 1680 .896

188 267 .704

(statistically significant difference: %2 ~ 5-64)

21

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only

Cars w. driver air bags

1208 1229 .983

196 201 .975

(not a statistically significant difference: %2 = 0.05)

Cars with belts only

Cars w. driver air bags

IN ALL CRASHES

4760 5390 .883

722 879 .821

(not a statistically significant difference: %2 = 1.80)

54
nonfrontal analysis, where adding in the models that got ABS at the same time as air bags biases the

results and necessitates an adjustment, as shown in Table C-18 of Appendix C, the additional accident

cases here do not inflict a systematic bias in favor of air bags. Table C-25 shows that, with the

extended sample, the fatality reduction by air bags for all occupants, regardless of their belt use, is

29 percent in pure frontals, 4 percent in partial frontals and 10 percent in all crashes. Those are

essentially the same results, give or take sampling error, as with the limited sample: 34 percent in pure

frontals, -2 percent in partial frontals and 10 percent in all crashes - see Tables 1-2 and 2-1.)

Table 3-2 estimates the fatality reduction for driver air bags in crashes where both front-seat

occupants were unbelted according to FARS (RESTJJSE or MANJREST = 0), using the limited

sample of make-models. The fatality reduction in purely frontal crashes is 34 percent, and it is

statistically significant at the .01 level (x2 = 7.92). In partially frontal crashes, fatality risk increases

by a nonsignificant 15 percent (x2 = 0.94). The net effect in all crashes is a nonsignificant 1 percent

reduction. When the accident sample is extended to all 1985-95 cars with 3-point belts, in Table

3-2X, the fatality reduction for air bags in purely frontal crashes is a statistically significant 32 percent

(X2= 11.61,p<.01). The observed effect in partially frontal crashes is still negative, but here it's

just -5 percent. The net effect in all crashes is a nonsignificant 4 percent reduction.

These analyses of drivers vs. right-front passengers strongly suggest that driver air bags are beneficial

for both belted and unbelted drivers in purely frontal crashes, as evidenced by statistically significant

reductions in three of the four tables. They also imply that the effect of air bags for belted drivers is

not too different from their effect for unbelted drivers, in the purely frontal crashes, the observed

reduction is slightly higher for unbelted drivers, but in partial frontals and overall, belted drivers have

slightly higher observed reductions. However, these analyses have a flaw that makes them unreliable

for assessing the overall effect of air bags: the fatality reduction in all crashes for belted drivers (5

percent in Tables 3-1 and 7 percent in Table 3-1X) and unbelted drivers (1 percent in Table 3-2 and

4 percent in Table 3-2X) do not average out to 11 percent, the overall, "as used" fatality reduction.

Evidently, air bags have a higher observed effect in the accident cases not used here: those where one

of the occupants was reported as belted and the other as unrestrained, or where one or both

occupants had unknown belt use. It is not clear why that happens; it might be tied to errors in belt

use reporting, but not necessarily.

The other analysis method of this report - comparison of fatalities in frontal and nonfrontal crashes,

as documented in Section 1.5 - employs only those accident cases in which a driver was a fatality.

Crashes where the driver survived never enter the analysis. Joksch has pointed out that this analysis

can be performed for just those driver fatalities that are reported as belted [unbelted] on FARS, and

since surviving drivers are not involved in the analysis, it relies only on FARS reports of belt use for

fatalities, not survivors [17]. If reporting of belt use is accurate in FARS for fatally injured people,

the frontal vs. nonfrontal method ought to provide unbiased "when used" estimates of fatality

reduction by air bags.

Table 3-3 computes the fatality reduction by air bags for belted drivers, based on the frontal vs.

nonfrontal method. It is limited to the "balanced" sample of makes, models and model years listed

in Table 1-1, and it excludes models that got Antilock Brake Systems at about the same time as air

bags. The top section of Table 3-3 shows that there were 603 belted purely frontal driver fatalities

55
TABLE 3-2 - UNBELTED DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

DRIVER AND RIGHT-FRONT SEATS BOTH OCCUPIED BY

PEOPLE NOT WEARING BELTS ACCORDING TO FARS

LIMITED DATA SET: MAKE-MODELS THAT HAD MANUAL OR AUTOMATIC 3-POINT BELTS

AND ADDED DRIVER AIR BAGS WITHOUT CHANGING THE BELT SYSTEM

Driver

Fatalities

Right Front

Fatalities

Risk

Ratio

Percent

Reduction

Cars with belts only

Cars w. driver air bags

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

359 355 1.011

99 149 .664

(statistically significant difference: %2 = 7-

9 2 )

34

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only

Cars w. driver air bags

295 314 .939

151 140 1.079

(not a statistically significant difference: X2~ 0.94)

-15

Cars with belts only

Cars w. driver air bags

IN ALL CRASHES

1008 1031 .978

451 • 468 .963

(not a statistically significant difference: x

2 = 0.03)

56
TABLE 3-2X - UNBELTED DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

DRIVER AND RIGHT-FRONT SEATS BOTH OCCUPIED BY

PEOPLE NOT WEARING BELTS ACCORDING TO FARS

EXTENDED DATA SET: ALL 1985-95 CARS WITH DRIVER AIR BAGS AND 3-POINT BELTS

VS. ALL 1985-95 CARS WITH 3-POINT BELTS ONLY

Driver

Fatalities

Right Front

Fatalities

Risk

Ratio

Percent

Reduction

Cars with belts only

Cars w. driver air bags

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

2654 2673 .993

137 203 .675

(statistically significant difference: x2 = 11.61)

32

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only

Cars w. driver air bags

2159 2112 1.022

207 193 1.073

(not a statistically significant difference: x

2 = 0.21)

-5

Cars with belts only

Cars w. driver air bags

IN ALL CRASHES

7483 7533 .993

619 651 .951

(not a statistically significant difference: %2 = 0.56)

57
TABLE 3-3 - BELTED DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS

WHO WORE BELTS ACCORDING TO FARS

LIMITED DATA SET: MAKE-MODELS THAT HAD MANUAL OR AUTOMATIC 3-POINT BELTS

AND ADDED DRIVER AIR BAGS WITHOUT CHANGING THE BELT SYSTEM,

EXCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 678 503

Purely frontal fatalities 603 351 22

(statistically significant difference: %2 ~ 7.39)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 678 503

Partially frontal fatalities 465 290 16

(not a statistically significant difference: x

2

 = 3.33)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 678 503

Frontal fatalities 1068 641 19

(statistically significant difference: x2 =

 7

-

5 5 )

Fatality reduction for driver air bags in all types of crashes: 12 percent

58
and 678 belted nonfrontal driver fatalities in the cars without air bags. But in cars equipped with air

bags, there were only 351 belted purely frontal driver fatalities as opposed to 503 belted nonfrontals.

The relative reduction of purely frontal fatalities by air bags, for belted drivers

1 - [(351/503) / (603/678)] = 22 percent

is statistically significant at the .01 level (x2 = 7.39). In partially frontal crashes, the reduction is a

nonsignificant 16 percent (x2 =3.33). In all types of crashes, this method estimates a statistically

significant 12 percent fatality reduction for the driver who has an air bag and wears belts, relative to

the driver who wears belts but has no air bag (x2 = 7.55,p<.01).

In an effort to include more accident cases, Table 3-3X extends the analysis to all model year 1985-95

cars with driver air bags and 3-point belts vs. all 1985-95 cars with 3-point belts only, including

models that got ABS at about the same time as air bags. That nearly doubles the sample of cars with

air bags and expands the sample of belt-only cars almost tenfold. However, as explained in Section

2.5, it introduces biases in favor of air bags, and requires adjustment of the results. After adjustment

of the results, the fatality reductions are slightly lower than in Table 3-3: the reduction is 19 percent

in purely frontal crashes, 9 percent in partially frontal crashes, and a net 7 percent in all types of

crashes.

Tables 3-4 and 3-4X perform corresponding analyses for the fatally injured drivers who were

unbelted according to FARS. In the limited accident data set, the fatality reduction by air bags is an

exceptionally strong, statistically significant 34 percent in purely frontal crashes (x2 = 26.82). The

observed reduction in partially frontal crashes is a nonsignificant 4 percent. The fatality reduction in

all types of crashes is 14 percent, and it is statistically significant (x2 = 11.26). The estimates for the

extended data set (Table 3-4X) are virtually identical, after adjustment for bias: reductions of 34

percent in purely frontal crashes, 7 percent in partially frontal crashes, and 14 percent in all crashes.

The analyses of frontals vs. nonfrontals likewise strongly suggest that driver air bags are beneficial

for both belted and unbelted drivers in purely frontal crashes: in both cases the reductions are

statistically significant at the .01 level (in Tables 3-3 and 3-4). However, these analyses, unlike the

driver vs. right-front computations, appear to suggest that air bags are somewhat more effective for

the unbelted than the belted driver in purely frontal crashes, and also in all frontal crashes. Are the

differences in the observed effectiveness estimates statistically significant? CATMOD analyses of

2x2x 2 tabulations of fatalities by crash mode (e.g., purely frontal vs. nonfrontal; or, alternatively,

any frontal vs. nonfrontal), belt use and type of occupant protection (driver air bag, no air bag)

produce mixed results. With the limited data set of matching make-models, the interaction term air

bag x belt use is nonsignificant (x2 = 1.99) when the dependent variable is the proportion of fatalities

that are pure frontals, and also when the dependent variable is the proportion of fatalities that are

frontal (x2 = 0.02). However, with the extended data set including all make-models in all model

years, the interaction term becomes statistically significant at the .01 level (x2 = 10.32) in the analysis

of pure frontals, but not in the analysis of all frontals (x2 = 2.72). Although the observed

effectiveness of air bags is higher for the unbelted occupant in all four of the analyses, it is

significantly higher in only one of them. In other words, the CATMOD analyses confirm our eyeball

interpretation of the results: they lean in the direction of higher air bag effectiveness for the unbelted

occupant, but not quite definitively so.

59
TABLE 3-3X- BELTED DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS

WHO WORE BELTS ACCORDING TO FARS

EXTENDED DATA SET: ALL 1985-95 CARS WITH DRIVER AIR BAGS AND 3-POINT BELTS

VS. ALL 1985-95 CARS WITH 3-POINT BELTS ONLY,

INCLUDING MAICE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Frontal Fat. Red.

for Air Bags (%)

Cars with Cars with

Belts Only Driver Air Bags Observed Adjusted

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 6437 994

Purely frontal fatalities 5873 683 25 19

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 6437 994

Partially frontal fatalities 4224 588 10

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 6,437 994

Frontal fatalities 10,097 1271 18 13

Fatality reduction for driver air bags in all types of crashes: 11 7

60
TABLE 3-4 - UNBELTED DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS

WHO WERE UNRESTRAINED ACCORDING TO FARS

LIMITED DATA SET: MAKE-MODELS THAT HAD MANUAL OR AUTOMATIC 3-POINT BELTS

AND ADDED DRIVER AIR BAGS WITHOUT CHANGING THE BELT SYSTEM,

EXCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 971 516

Purely frontal fatalities 1136 400 34

(statistically significant difference: x2 = 26.82)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 971 516

Partially frontal fatalities 917 469 4

(not a statistically significant difference: x

2 = 0.24)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 971 516

Frontal fatalities 2053 869 20

(statistically significant difference: %2 = 11.26)

Fatality reduction for driver air bags in all types of crashes: 14 percent

61
TABLE 3-4X- UNBELTED DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS

WHO WERE UNRESTRAINED ACCORDING TO FARS

EXTENDED DATA SET: ALL 1985-95 CARS WITH DRIVER AIR BAGS AND 3-POINT BELTS

VS. ALL 1985-95 CARS WITH 3-POINT BELTS ONLY,

INCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Frontal Fat. Red.

for Air Bags (%)

Cars with Cars with

Belts Only Driver Air Bags Observed Adjusted

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 9,740 985

Purely frontal fatalities 12,192 734 40 34

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 9,740 985

Partially frontal fatalities 9,225 860 8

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 9,740 985

Frontal fatalities 21,417 1594 26 21

Fatality reduction for driver air bags in all types of crashes: 18 14

62
Whereas, in the frontal vs. nonfrontal analyses, the average of the overall effects for belted and

unbelted drivers comes out close to 11 percent, there is still a problem that raises a question about

the data: when the same method is applied to the FARS cases of driver fatalities with unknown belt

use, as shown in Tables C-26 and C-27, all of the observed fatality reductions for air bags are close

to zero or negative (although nonsignificant), even in purely frontal crashes. It is not clear why that

happens, it might conceivably indicate a problem in belt use reporting, but not necessarily.

Table 3-5 summarizes all of the preceding results based on FARS-reported belt use. The fatality

reduction for air bags is analyzed four times, in each of three crash modes (purely frontal, partially

frontal, all crashes) for belted drivers (top section) and unbelted drivers (lower section). The

estimates from the four analyses are averaged. But they are weighted averages. Since the two

frontal vs. nonfrontal analyses rely only on belt use reporting for fatally injured occupants, they are

more dependable than the two driver vs. right-front passenger analyses, so they are given double

weight in the computation of the average.

In purely frontal crashes, Table 3-5 indicates a weighted average of 21 percent fatality reduction for

belted drivers and nearly 34 percent for unbelted drivers; moreover, in all four individual analyses,

the observed reduction is higher for the unbelted drivers. Approximate 90 percent confidence bounds

(i.e., two-sided a = .05) for the fatality reductions in purely frontal crashes may be developed from

the entries in the top sections of Tables 3-3 and 3-4, using the same method as in Section 2.1. The

confidence bounds of the fatality reduction for belted drivers are 9 to 33 percent. The confidence

bounds for the unbelted drivers are 25 to 42 percent.

The higher effectiveness of air bags for unbelted drivers in purely frontal crashes is somewhat offset

in the partially frontal crashes, where the average reduction is 8.3 percent for the belted drivers and

close to zero for the unbelted; here, in each of the four individual analyses, the observed result is

better for the belted drivers. For all types of crashes, the weighted average fatality reduction by air

bags is 8.3 percent for belted drivers and 10.2 percent for unbelted drivers. These two estimates do

not average to 11 percent and, for that reason, should not be considered the "best" estimates of

effectiveness. The concluding section of this chapter (Section 3.4) will further develop estimates of

overall effectiveness, and their confidence bounds.

3.3 Analyses that do not rely on FARS belt use reporting

If air bags are more effective for the unbelted than the belted occupant, we ought to see the highest

air bag effectiveness in the States with the lowest belt use. Conversely, if we fail to see higher air bag

effectiveness in the States with the lowest belt use, it might raise doubts about the earlier finding that

air bags are more effective for unrestrained occupants. The analyses of this section identify a group

of drivers (by State, etc.) that has high belt use, and another group that has low belt use, and they

compare the effectiveness of air bags in the two groups. But it is not known whether any individual

driver in the first group was, in fact, wearing belts, or any individual in the second was, in fact,

unrestrained. For that reason, these analyses are not intended as a proxy for the previous section, in

which drivers were grouped by their actual [as-reported] belt use. Instead, their purpose is to test

and, hopefully, support the findings in Table 3-5. The reason for performing the analyses is the

uncertainty, of some researchers, about the accuracy of belt-use reporting on FARS. Potential

63
TABLE 3-5: FATALITY REDUCTION BY CAR DRIVER AIR BAGS

FOR BELTED VS. UNBELTED DRIVERS, BY IMPACT LOCATION

SUMMARY OF ESTIMATES BASED ON FARS-REPORTED BELT USE

Percent Fatality Reduction by Air Bags

Analysis Method

Compare Driver to Right Front Compare Frontal to Nonfrontal

For belted drivers

Purely frontal impacts

Partially frontal impacts

All crashes

For unbelted drivers

Purely frontal impacts

Partially frontal impacts

All crashes

Matching

Make-Models*

23

-1

5

34

- 15

1

All MakeModels*

21

1

7

32

-5

4

Matching

Make-Models*

22

16

12

34

4

14

All Make-Models

(Adjusted)

19

9

7

34

7

14

Weighted§

Average

21

8.3

8.3

33.7

0.3

10.2

* Statistically significant results are shown in bold italics.

Estimates based on frontal vs. nonfrontal analyses are given double weight.
skepticism about results based directly on belt-use reporting in FARS may be allayed if those results

are confirmed by analyses that do not rely on FARS-reported belt use.

Even without the belt-use variable on FARS, it is possible to recognize some drivers who were likely

to have been belted, and others who were less likely. Three factors that can be ascertained from other

FARS variables have a strong association with belt use:

• State/calendar year - belt use by the general motoring population is much higher in a State

with a widely-enforced belt use law than in a State without a buckle-up law. It ranged from 22

percent in Mississippi during 1990 to 85 percent in Hawaii during 1991.

• Sobriety - belt use is substantially higher for sober drivers than for drunk drivers.

• Vehicle age - belt use decreases steadily as a car gets older [4], p. 23.

The expected probability of belt use will be assessed for each car driver in 1989-96 FARS, by a

model based on the State and the calendar year of the accident, the driver's sobriety, and the age of

the car. For example, the model might predict in a certain crash situation (State, calendar year,

sobriety, vehicle age) that 75 percent of drivers involved in that crash situation would be belted, and

25 percent unbelted. The various fatal crashes on 1989-96 FARS will be divided into four class

intervals of expected belt use: 68-100, 57-68, 40-57 and 0-40. The fatality reduction for air bags will

be calculated in each of the four subsets by the frontal vs. nonfrontal analysis method. If the four

effectiveness estimates show a trend of increasing [decreasing] effectiveness as expected belt use

declines, it would imply that air bags are more [less] effective for unrestrained than belted drivers.

But if the four estimates do not show a trend, they would be consistent with the hypothesis that air

bags are about equally effective for belted and unbelted drivers.

The logistic model is well-suited for calibrating expected belt use, since there tend to be linear

relationships between the various factors discussed above and the log-odds of belt use (i.e., the

logarithm of the ratio of belt users to nonusers). The starting point for the model is the aggregate belt

use of fatally injured drivers of cars less than 3 years old, equipped with manual 3-point belts (with

or without air bags, but no automatic belts), as reported on FARS, excluding cases with unknown

belt use, by calendar year:

Belt Use of Fatally Injured Car Drivers

Calendar Year Belt Use (%) Log-Odds

1989 31.7 -.768

1990 34.4 - .642

1991 39.8 - .413

1992 45.3 -.190

1993 47.7 - .094

1994-96 . 48.9 - .044

65
The next step is to infer belt use in potentially fatal crashes - i.e., crashes that were fatal to the

driver plus crashes that were survived by a belted driver, but would have been fatal if belts had not

been used [24]. Since a driver wearing a manual 3-point belt has 45 percent lower fatality risk than

an unrestrained driver under similar crash circumstances [13], p. IV-2, 55 belted fatalities on FARS

presumably represent 100 drivers who were belted and involved in a potentially fatal crash. The logodds of belt use in potentially fatal crashes is simply the log-odds for fatals plus 0.598 = log(l/.55).

Belt use declines as a car gets older. The reasons for the decline are not known; it is possible that

people who drive older cars are generally less safety-conscious than those who drive new cars.

Whatever the reason, the relationship between vehicle age and the log-odds of belt use by drivers

who were fatally injured, or who were in potentially fatal crashes, is almost perfectly linear for cars

age 0-10 years. A General Linear Model [27] of 1989-95 FARS data, celled by calendar year and

vehicle age and weighted by the number of cases, suggests that the log-odds for cars less than a year

old is 0.095 higher than the average log-odds for cars 0-2 years old, in any given calendar year. For

each year that a car gets older, the log-odds decrease by 0.0787. R2 for this regression is .75.

The effect of sobriety on the log-odds of belt use is quite consistent throughout 1989-95. For fatally

injured drivers that had not been drinking, according to FARS (DRINKING = 0), the log-odds of belt

use was 0.391 higher than the average for all drivers. For driver fatalities that had been drinking

according to FARS (DRINKING = 1), the log-odds of belt use was 0.976 lower than average. For

all other driver fatalities - those whose alcohol consumption was unknown or not reported - the logodds of belt use was 0.009 lower than average.

State-to-State variations in belt use are documented in observational surveys of the general motoring

population, conducted by the States themselves. The surveys are based on eye-witness observations

of representative samples of drivers not involved in crashes. Appendix D shows belt use in each

State, by calendar year from 1990 to 1994, and also the population-weighted national averages of the

values from the 50 States and the District of Columbia. For the general population (not in potentially

fatal crashes), belt use in the United States rose from 53.09 percent in 1990 to 66.96 percent in 1994,

and its log-odds rose from +0.1238 in 1990 to +0.7064 in 1994. A belt-use factor for any particular

State and calendar year is computed by taking the log-odds of belt use for that State and year, and

subtracting from it the national log-odds for that year. For example, observed belt use was 42 percent

in Alabama in 1990, and its log-odds were -0.3228. Since the national log-odds for 1990 was

+0.1238, the Alabama-1990 factor is -0.4466. Thus, in potentially fatal crashes, the log-odds of belt

use by a driver in Alabama during 1990 is .4466 lower than the log-odds for the average driver

nationwide. These State-year factors can be defined directly from Appendix D for 1990-94. To

expand the data available for analysis, it is assumed that the 1990 factors are also reasonably accurate

for 1989, and the 1994 factors for 1995-96.

The expected belt use for any driver on FARS may be calculated by adding the various factors, and

then converting the log-odds back to a percentage. For a sober driver of a new car in Hawaii during

1995, the factors are:

66
- .044 Calendar year 1995 log-odds of belt use for fatals

+ .598 Belt use in potentially fatal crashes

+ .095 Car less than 1 year old

+ .391 Sober driver

+ .952 Hawaii 1994/95 belt use vs. U.S. average

+ 1.992

and the expected belt use is 88 percent [exp 1.992 / (1 + exp 1.992)]. On the other hand, for a drunk

driver of a 1985 car in Mississippi during 1990, the factors are:

- .642 Calendar year 1990 log-odds of belt use for fatals

+ .598 Belt use in potentially fatal crashes

- .299 Car 5 years old

- .976 Drinking driver

- 1.389 Mississippi 1990 belt use vs. U.S. average

- 2.708

and the expected belt use is 6 percent [exp -2.708 / (1 + exp -2.708)]. The values of expected belt

use in potentially fatal crashes for the 1989-96 FARS cases fill up the range of possibilities between

these rather extreme values of 6 and 88 percent.

The 1989-96 FARS cases of fatally injured drivers, in cars equipped with driver air bags and 3-point

belts or just with 3-point belts, are subdivided into four ranges of expected belt use: 68-100, 57-68,

40-57 and 0-40. The boundaries of the ranges were selected so that each group has about the same

number of air-bag equipped cases; all four groups contain plenty of cars without air bags, but it is the

air-bag equipped sample size that drives the statistical analysis. The average values of expected belt

use in the four ranges are 75, 62, 49 and 29 percent, respectively. In other words, we can be quite

sure that the first group contains a high proportion of belt users, and the last group a low one,

without having to worry that drivers have been placed into the wrong groups as a consequence of

possible errors of belt-use reporting on FARS.

Table 3-6 summarizes the analyses of fatality reduction by air bags in each of the four groups, based

on the comparison of fatalities in frontal vs. nonfrontal crashes. The top section of Table 3-6

considers drivers with the highest expected belt use, and the bottom section the lowest to simplify

comparison with Table 3-5, which addresses belted drivers in the top section and unbelted in the

lower section. The detailed analyses may be found in Tables C-28 - C-35 of Appendix C. For

example, Table C-28 is limited to vehicle cases of the specific makes, models and model years defined

in Table 1-1, and it analyzes drivers with expected belt use over 68 percent. The fatality reduction

by driver air bags in purely frontal crashes is 31 percent for these drivers, and it is statistically

significant at the .01 level (x2 = 7.97). The observed effect of driver air bags in partially frontal

crashes is a nonsignificant 21 percent increase. The net effect in all types of crashes is a

nonsignificant 8 percent reduction. These numbers, 31,-21 and 8, are shown in the first column of

the upper section of Table 3-6.

67
TABLE 3-6: FATALITY REDUCTION FOR CAR DRIVER AIR BAGS

BY EXPECTED BELT USE AND IMPACT LOCATION

EXPECTED BELT USE IS BASED ON THE DRIVER'S

STATE, ALCOHOL STATUS, VEHICLE AGE AND THE CALENDAR YEAR

Percent Fatality Reduction by Air Bags

Analysis Method:

Compare Frontal to Nonfrontal

Expected belt use over 68 percent

(average: 75 percent)

Purely frontal impacts

Partially frontal impacts

All crashes

Matching

Make-Models*

31

-21

8

All Make-Models

(Adjusted)

20

- 9

4

Expected belt use 57-68 percent

(average: 62 percent)

Purely frontal impacts

Partially frontal impacts

All crashes

Expected belt use 40-57 percent

(average: 49 percent)

Purely frontal impacts

Partially frontal impacts

All crashes

17

- 2

5

40

18

20

21

- 4

5

33

8

13

Average

25.5

15

6

19

-3

5

36.5

13

16.5

Expected belt use 0-40 percent

(average. 29 percent)

Purely frontal impacts

Partially frontal impacts

All crashes

29

13

11

28

15

14

23.5

14

12.5

* Statistically significant results are shown in bold italics.

68
Table C-29 extends the analysis of drivers with expected belt use over 68 percent to all 1985-95 cars

with 3-point belts and, possibly, driver air bags, including models that got ABS at the same time as

air bags. After adjustment for the biases that are introduced by including cars that got ABS with air

bags, the fatality reductions for air bags are 20 percent in pure frontals, -9 percent in partial frontals

and 4 percent in all crashes. These are shown in the second column of the top section of Table 3-6.

The averages of the fatality reductions in the limited and extended (adjusted) analyses are shown in

the last column of Table 3-6: 25.5 percent reduction in pure frontals, 15 percent increase in partial

frontals, 6 percent reduction in all crashes for drivers with over 68 percent expected belt use.

The three lower sections of Table 3-6 present corresponding results for drivers less likely to have

buckled up. At first glance, Table 3-6 shows a probable, but not obvious trend toward higher fatality

reduction by air bags for successively less belted groups of drivers. In every crash mode, the average

effectiveness of air bags for the two groups with low expected belt use, combined, is higher than the

corresponding average for the two high-belt-use groups, combined. In most cases, the effectiveness

estimates for each of the two low-belt-use groups are higher than the corresponding estimates for

either high-belt-use group. Nevertheless, the trend is not monotone or linear. In general, the drivers

with 57-68 percent expected belt use have the worst results for air bags (e.g., only 5 percent observed

fatality reduction in all types of crashes), while the drivers with 40-57 percent belt use tend to have

the best results (36.5 percent reduction in pure frontals and 16.5 percent in all crashes). The two

extreme belt use groups (over 68 and under 40 percent) have results that are mostly between those

for the two middle groups. Also, none of the four groups yields results that are grossly different,

considering the sample sizes, from the fatality reductions for all drivers combined: 27 percent in pure

frontals, 6 percent in partial frontals and 11 percent in all crashes (Tables 2-2 and 1-3).

The search for trends is simplified by looking at just the average belt use in each of the four groups,

and the average values of fatality reduction in each crash mode:

Belt Use (%)

75

62

49

29

Pure Frontals

25.5

19

36.5

23.5

Fatality Reduction by Air Bags (%)

Partial Frontals

-15

-3

13

14

All Crashes

6

5

16.5

12.5

The fatality reductions in pure frontals, 25.5, 19, 36.5, 23.5 do not show a trend, but the average for

the two low-belt-use groups is somewhat higher than the average for the two high-belt-use groups,

consistent with the differences seen in the analyses based on FARS belt-use reporting (Table 3-5).

The observed effects in partial frontals show a monotone, but not linear pattern of more positive

results as belt use decreases. The only problem is that the analyses based on FARS-reported belt use,

as documented in Table 3-5, leaned toward the opposite result. When the two sets of results are

viewed together, it is really not possible to draw any conclusion on partial frontals. The four

reductions in crashes of all types, 6, 5, 16.5 and 12.5 percent do not have a monotone trend, but they

still suggest, unmistakably, that air bag effectiveness is higher in the low belt use groups.

69
CATMOD analyses of 2 x 4 x 2 tabulations of fatalities by crash mode (e.g., purely frontal vs.

nonfrontal; or, alternatively, any frontal vs. nonfrontal), expected-belt-use group (4 groups, but

expected belt use is treated as a linear variable with values .75, .62, .49 and .29) and type of occupant

protection (driver air bag, no air bag) produce mixed results. With the limited data set of matching

make-models, the interaction term air bag x expected belt use is close to zero when the dependent

variable is the proportion of fatalities that are pure frontals; when the dependent variable is the

proportion of fatalities that are frontal, the interaction term is in the expected direction (i.e., air bags

become less effective in reducing fatalities as expected belt use increases) but not statistically

significant (%2 =1.16). However, with the extended data set including all make-models in all model

years, both of these interaction terms are statistically significant and in the expected direction

(X2 = 4.90 and 8.99, respectively).

3.4 Summary

The two principal findings of the analyses of air-bag effectiveness based on actual belt use as reported

in FARS were that (1) air bags significantly reduce fatality risk for belted as well as unbelted drivers,

as evidenced by a multitude of statistically significant results; (2) there is substantial, but not quite

conclusive evidence that the effectiveness of air bags is higher for the unbelted than for the belted

driver. The analyses of air bag effectiveness for four expected-belt-use groups strongly support both

of those findings.

Section 3.2 presented "when used" effectiveness estimates for air bags in purely frontal crashes: air

bags reduced the fatality risk of an unbelted driver by nearly 34 percent; the fatality risk of a belted

driver with air bags was 21 percent lower than the fatality risk of a belted driver without air bags.

Now, let us try to develop corresponding "when used" estimates for all types of crashes. As stated

at the beginning of this chapter, the two estimates must average to 11 percent, the "as used"

effectiveness of air bags for all drivers (and, for all practical purposes, it will be satisfactory if the

simple arithmetic average of the two estimates is 11 percent, since about half of driver fatalities are

currently belted, and half unbelted).

It is unlikely that both "when used" reductions are 11 percent: there is simply too much evidence that

air bags are more effective for unbelted drivers than for belted drivers. The analyses of Section 3.2

furnished point estimates of 10.2 percent for unbelted drivers and 8.3 percent for belted drivers. If

both estimates are revised upwards until they average to 11 percent (and rounded to whole numbers),

they suggest a 12 percent reduction for unbelted drivers and a 10 percent reduction for belted drivers.

However, those numbers still seem too close together. The results for purely frontal crashes suggest

that the effect of air bags is about VA times as large for unbelted drivers as for belted drivers, and the

results for the expected-belt-use groups also suggest that air bags are perceptibly more effective for

the unbelted driver.

When all of the results are taken into account, the best point estimates would appear to be a 13

percent fatality reduction by air bags for unbelted drivers and a 9 percent incremental fatality

reduction by air bags for belted drivers. These point estimates, however, are difficult to interpret

without confidence bounds. Approximate 90 percent confidence bounds (i.e., two-sided a = .05) may

be developed from the entries in the lowest sections of Tables 3-3 and 3-4, using the same method

70
as in Section 1.5. The confidence bounds of the overall fatality reduction for unbelted drivers are 7

to 19 percent. The confidence bounds of the incremental fatality reduction by air bags for belted

drivers are 3 to 15 percent. In other words, there is considerable overlap between the two confidence

intervals. Furthermore, both point estimates of "when-used" effectiveness (13 and 9 percent) are

within the current confidence bounds for "as used" effectiveness (7 to 15 percent; see Section 1.5).

Based on these findings, a preliminary prediction can be made that the current "as used" fatality

reduction for air bags, 11 percent, is unlikely to change radically if safety belt use increases

substantially in the future, because the "when used" reductions for belted and unbelted occupants are

both positive, and probably neither is too far away from 11 percent. The difference between the two

"when used" estimates is within the current noise range of the "as used" estimate. Even if belt use

were to rise above 90 percent, air bags would continue to provide effective supplemental protection

according to the current data.

71

REFERENCES

[I] Automotive News Market Data Book Issue. Annual Publication. Detroit: Crain Automotive

Group, Inc.

[2] Code of Federal Regulations, Title 49. Washington: General Printing Office, 1994.

[3] Consumer Information: Automatic Crash Protection for Passenger Cars. Annual

Publication, 1987-93. Washington: National Highway Traffic Safety Administration, Office

of Public and Consumer Affairs.

[4] Datta, Tapan K., and Guzek, Paul. Restraint System Use in 19 U. S. Cities, 1989 Annual

Report. Report No. DOT HS 807 595. Washington: National Highway Traffic Safety

Administration, [1990].

[5] Effect of Car Size on Fatality and Injury Risk. Washington: National Highway Traffic

Safety Administration, [1991].

[6] Evaluation of the Effectiveness of Occupant Protection: Federal Motor Vehicle Safety

Standard 208, Interim Report. Technical Report No. DOT HS 807 843. Washington:

National Highway Traffic Safety Administration, [1992].

[7] Evans, Leonard. "Double Pair Comparison - A New Method to Determine How Occupant

Characteristics Affect Fatality Risk in Traffic Crashes." Accident Analysis an Prevention

18 (June 1986).

[8] . Traffic Safety and the Driver. New York: Van Nostrand Reinhold, 1991.

[9] FARS1995 Coding and Validation Manual. Washington: National Highway Traffic Safety

Administration, National Center for Statistics and Analysis [1995].

[10] Federal Register 49 (17 July 1984): 28962.

[II] Federal Register 55 (17 January 1990): 1586.

[12] Federal Register 58 (4 October 1993): 51735.

[13] Final Regulatory Impact Analysis, Amendment to Federal Motor Vehicle Safety Standard

208, Passenger Car Front Seat Occupant Protection. Report No. DOT HS 806 572.

Washington: National Highway Traffic Safety Administration, [1984].

[14] Healy, James R., and O'Donnell, Jayne. "Deadly Air Bags." USA Today, July 8, 1996.

73
[15] Hertz, Ellen; Hilton, Judith; and Johnson, Delmas M. An Analysis of the Crash Experience

of Light Trucks Equippedwith Antilock Brake Systems. Technical Report No. DOT HS 808

278. Washington: National Highway Traffic Safety Administration, [1995],

[16] . An Analysis of the Crash Experience of Passenger Cars Equipped with Antilock

Brake Systems. Technical Report No. DOT HS 808 279. Washington: National Highway

Traffic Safety Administration, [1995].

[ 17] Joksch, Hans C. Airbag Fatalities Approximation for Passenger Car Fleet. To appear in

1996.

[18] Kahane, Charles J. Correlation ofNCAP Performance with Fatality Risk in Actual HeadOn Collisions. Technical Report No. DOT HS 808 061. Washington: National Highway

Traffic Safety Administration, [1994].

[19] . "Fatality Reduction by Automatic Occupant Protection in the United States"

Proceedings of the Fourteenth International Technical Conference on the Enhancement of

Safety in Vehicles. Washington: National Highway Traffic Safety Administration, [1994].

[20] . Preliminary Evaluation of the Effectiveness of Antilock Brake Systems for

Passenger Cars. Technical Report No. DOT HS 808 206. Washington. National Highway

Traffic Safety Administration, [1994].

[21] National Vehicle Population Profile. Annual Publication. Detroit: R. L. Polk.

[22] NHTSA Docket 01-22-N1 IB (Manufacturers' explanations of VIN as required by 49 CFR

565.5).

[23 ] NHTSA Hails Safety Features in Model Year 1994 Passenger Cars and Light Trucks and

Vans. Press Release No. NHTSA 38-93. Washington: U. S. Department of Transportation,

Office of the Assistant Secretary for Public Affairs, [1993].

[24] Partyka, Susan C. Lives Saved by Seat Belts from 1983 through 1987. NHTSA Technical

Report No. DOT HS 807 324. Washington: National Highway Traffic Safety

Administration, [1988].

[25] Passenger Vehicle Identification Manual. Annual Publication. Palos Hills, IL: National

Insurance Crime Bureau.

[26] Perkins, David D.; Cynecki, Michael J.; and Goryl, Michael E. Restraint System Usage in

the Traffic Population, 1983 Annual Report. Report No. DOTHS 806 582. Washington:

National Highway Traffic Safety Administration, [1984].

[27] SAS User's Guide: Statistics, Version 5 Edition. Cary, NC: SAS Institute, Inc., 1985.

74
[28] Secretary Pena Announces Government/Industry Coalition for Air Bag Safety. Press

Release No. NHTSA 24-96. Washington: U. S. Department of Transportation, Office of

the Assistant Secretary for Public Affairs, [1996].

[29] Zador, Paul L., and Ciccone, Michael A. Driver Fatalities in Frontal Impacts:

Comparisons between Cars with Air Bags and Manual Belts. Insurance Special Report No.

A-38. Arlington, VA: Insurance Institute for Highway Safety, [1991].

75

APPENDIX A

PASSENGER CARS

TYPES OF OCCUPANT PROTECTION BY MAKE-MODEL AND YEAR

EXPLANATION OF CODES

make-model was not sold in this model year

0 manual 3-point belts for driver and right-front (RF) passenger

9 occupant protection system unknown - or - 2 or more types offered that year,

but VTN does not specify which type is on a particular vehicle

303 motorized 2-point belts without disconnect + manual lap belts for driver and RF

404 motorized 2-point belts with disconnect + manual lap belts for driver and RF

505 nonmotorized 3-point [automatic] belts for driver and RF

606 nonmotorized 2-point belts + manual lap belts for driver and RF

707 nonmotorized 2-point belts for driver and RF (no lap belts, knee bolster only)

1000 driver air bag + manual 3-point belts for driver and RF

1003 air bag + manual 3-point belt for the driver,

motorized 2-point belt without disconnect + manual lap belt for the RF

1004 air bag + manual 3-point belt for the driver,

motorized 2-point belt with disconnect + manual lap belt for the RF

1006 air bag + manual 3-point belt for the driver,

nonmotorized 2-point belt + manual lap belt for the RF

1010 dual air bags + manual 3-point belts for driver and RF

1303 driver air bag +

motorized 2-point belts without disconnect + manual lap belts for driver and RF

1313 dual air bag +

motorized 2-point belts without disconnect + manual lap belts for driver and RF

1404 driver air bag +

motorized 2-point belts with disconnect + manual lap belts for driver and RF

1505 driver air bag +

nonmotorized 3-point [automatic] belts for driver and RF

1606 driver air bag +

nonmotorized 2-point belts + manual lap belts for driver and RF

Note: If two or more types of occupant protection were offered in the same year, and the VIN can

be used to identify which type is on a particular vehicle, the first type is shown on the first line, the

second type on the second line, etc. Codes marked with a "?" are not used in the analyses.

77
Valid Occupant Protection Codes

Car Group

Make/Model 85 86 87 88 89 90 91 92 93 94 95

111 AMCEagle

109 AMC Eagle 0 0 0 0 ...... .

112AMCSX4

110AMCSX4/Kammback 0 0 ........ .

614 Aspen/Volare 4 door

610 Chrysler 5th Avenue

707 Dodge Diplomat

904 Plymouth Gran Fury

615 Omni/Horizon 4 door

708 Dodge Omni 4 door

908 Plymouth Horizon 4 dr

616 Omni/Horizon 2 door

708 Dodge Omni 2 door

908 Plymouth Horizon 2 dr

618 Aries/Reliant K

616 Chrysler LeBaron (except GTS)

616 Chrysler LeBaron coupe

616 Chrysler LeBaron convertible

711 Dodge Aries

714 Dodge 600 2 door

911 Plymouth Reliant

619 Chrysler E-Class

614 Chrysler E-Class/New Yorker

616 Chrysler LeBaron GTS

714 Dodge 600 4 door

716 Dodge Lancer

907 Plymouth Caravelle

620 Daytona/Sundance

615 Chrysler Laser

715 Dodge Daytona

717 Dodge Shadow

917 Plymouth Sundance

621 Dodge Dynasty

618 Chrysler New Yorker C

718 Dodge Dynasty

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

606

0

0

0

0

0

0

0

0

0

606

0

0

0

1000

0

1000

0

1000

0

0

0

606

1000

1606

0

0

0

0

0

0

0

0

606

1000

1606

0

404

0

404

0

0

1000

1000

1000

0

0

0

1000

0

0

0

0

1000

0

404

0

404

0

0

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000 1010

1010

1000

1000 1004

1000 1004

1000

1000

78
Car Group

Make/Model

622 Plymouth Acclaim

616 Chrysler LeBaron sedan

719 Dodge Spirit

919 Plymouth Acclaim

623 Chrysler Imperial 109

620 Chrysler 5th Ave/Imperial

624 Dodge Viper

713 Dodge Viper

625 Chrysler LH cars

641 Chrysler Concorde

642 Chrysler LHS/New Yorker

650 Chrysler Concorde/LHS/New Yorker

741 Dodge Intrepid

1041 Eagle Vision

626 Chrysler Cirrus/Stratus

644 Chrysler Cirrus

743 Dodge Stratus

627 Chrysler Neon

720 Dodge Neon

920 Plymouth Neon

1226 Fairmont/Zephyr

1206 Ford LTD

1406 Mercury Marquis

1227 Ford Mustang 100

1203 Ford Mustang

1403 Mercury Capri

1228 Crown Vic/Grand Marquis

1216 Ford Crown Victoria

1416 Mercury Grand Marquis

1230 Lincoln Town Car

1301 Lincoln Town Car

1231 Ford Escort

1213 Ford Escort

1214 Ford EXP

1413 Mercury Lynx

1232 Lincoln Mark7

1302 Lincoln Mark7

1305 Lincoln Continental

Valid Occupant Protection Codes

85 86 87 88 89 90 91 92 93 94 95

1000 1000 1000 1000 1004

0 1000 1000 1000 1000 1004 1004

0 1000 1000 1000 1000 1004 1004

1000 1000 1000 1000

505 505 505 505

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

0 0

0 0

0 0 0 0 0 1000 1000 1000 1000

0 0

0 0 0 0 1000 1000 1000 1000 1010 1010

1010 1010

0 0 0 0 1000 1000 1000 1010 1010 1010

1010

0 0 0 0 1000 1000 1010 1010 1010 1010

1010 1010

0

0

0

0

0

0

0

0

0

0

0

303

0

0

303

0

0

9

303

0

0

303

0

303

1000 1000 1000

79
Car Group

Make/Model

1233 Ford Thunderbird 104

1204 Ford Thunderbird

1404 Mercury Cougar

1234 Ford Tempo

1215 Ford Tempo

1415 Mercury Topaz

1235 Ford Taurus

1217 Ford Taurus

1417 Mercury Sable

1236 Lincoln Continental 109

1305 Lincoln Continental

1237 Ford Thunderbird 113

1204 Ford Thunderbird

1302 Lincoln Mark8

1404 Mercury Cougar

1238 Ford Mustang 101.3

1203 Ford Mustang

1239 Ford Contour

1235 Ford Contour

1437 Mercury Mystique

Valid Occupant Protection Codes

85 86 87 88 89 90 91 92 93 94 95

0

0

0

0

0 303 303 303 303 303 303 303

1000 1000 1000 1000 1000 1000 1000 1003

0 303 303 303 303 303 303 303

1000 1000 1000 1000 1000 1000 1000 1003

0

0

0

0

0

0

0

0

1000

1000

1000

1000

1000

1010

1000

1010

1000

1010

1010

1010

1010

1010

1010

1838 Chevrolet Chevette 94.3

2013 Chevrolet Chevette 2 dr

2213 Pontiac T1000 2 dr

0

0

0

0

0

0

0 1000 1000 1000 1010 1010 1010 1010

1010 1010 1010

303 303 303 303 303 1010 1010

1010 1010 1010

303 303 303 303 303 1010 1010

1010 1010

1010

1010

1839 GM full-sized sedan 116

1802 Buick LeSabre sedan

1804 Buick Roadmaster sedan

2002 Chevrolet Caprice sedan

2102 Olds Delta 88 sedan

2202 Pontiac Parisienne

1840 GM full-sized wagon 116

1802 Buick Estate Wagon

1804 Buick Roadmaster wagon

2002 Chevrolet Caprice wagon

2102 Olds Custom Cruiser

2202 Pontiac Safari

1842 Cadillac DeVille 121.5

1903 Cadillac Heetwood Brougham

1903 Cadillac Fleetwood

0

0

0

0

0

0

1000 1000 1010 1010

505 1000 1000 1000 1010 1010

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

505

505

505

505

1000

1000

1000

505

1000

1000

1000

505

1000

1000

1000

1000

1010

1010

1010

1010

1010

1010

1010

80
Valid Occupant Protection Codes

Car Group

Make/Model 85 86 87 88 89 90 91 92 93 94 95

1843 Chevrolet Chevette 97.3

2013 Chevrolet Chevette 4 dr

2213 Pontiac T1000 4 dr

1844 GM Intermediates 108.1

1801 Buick Regal 4 door

2101 Olds Cutlass 4 door

2202 Pontiac Bonneville 4 dr

1845 GM Sporty Intermediates 108.1

1810 Buick Regal 2 door

2010 Chevrolet Monte Carlo

2101 Olds Cutlass 2 door

2202 Pontiac Bonneville 2 dr

2210 Pontiac Grand Prix

1846 GM Luxury Sports 114

1805 Buick Riviera

1905 Cadillac Eldorado

1914 Cadillac Seville

2105 Oldsmobile Toronado

1847 GM Compact X cars

1815 Buick Skylark

2015 Chevrolet Citation

1848 GM Compact J cars

1816 Buick Skyhawk

1916 Cadillac Cimarron

2016 Chevrolet Cavalier

2116 Olds Firenza

2216 Pontiac Sunbird

1849 Chevrolet Camaro F 101

2009 Chevrolet Camaro

2209 Pontiac Firebird

1850 GM Mid-sized A 104.9

1817 Buick Century

2017 Chevrolet Celebrity

2117OldsCiera

2217 Pontiac 6000

1851 Chevrolet Corvette Y 96.2

2004 Chevrolet Corvette 0 0 0 0 0 1000 1000 1000 1000 1010 1010

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

505

505

1000

1000

505

505

505

505

505

505

1000

1000

505

505

505

505

505

1000

1000

505

505

505

505

1010

1010

505

1505

505

1505

505

505

1010

1010

1505

1505

1010

1010

1505

1505

81
0

0

0

0

0

0

0

0

0

0

505

0

0

0

505

0

0

505

505

0

0

505

1000

0

505

505

505

0

1000

505

1000

505

1000

505

505

505

1000

505

1000

505

1000

505

505

1000

1000

505

1000

1000

505

1000

1000

1000

1000

1000

1000

1010

1000

1000

1000

1010

1000

1000

1000

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

Valid Occupant Protection Codes

Car Group

Make/Model 85 86 87 88 89 90 91 92 93 94 95

1852 GM Luxury C and Full-sized H 110.8

1802BuickLeSabre

1803BuickElectra

1903 Cadillac DeVille

1903 Cad DeVille coupe

2102 Olds Delta 88

2103 Olds 98

2202 Pontiac Bonneville

1853PontiacFieroP

2205 Pontiac Fiero

1854 Pontiac Grand Am N 103.4

1818 Buick Somerset/Skylark

2118 Olds Calais

2121 Olds Achieva

2218 Pontiac Grand Am

1855 GM luxury sports cars E and Cadillac Seville K 108

1805 Buick Riviera

1905 Cadillac Eldorado

1914 Cadillac Seville

2105 Oldsmobile Toronado

1856 Chevrolet Corsica/Beretta L

2019 Chevrolet Corsica

2019 Chevrolet Beretta

1857 Cadillac AUanteV

1909 Cadillac Allante .00 0 1000 1000 1000 1000

1858 Buick Rearta EC

1821 Buick Reatta

1859 GM Mid-sized W 107.5

1820 Buick Regal

2020 Chevrolet Lumina

2036 Chevrolet Monte Carlo

2120 Olds Cutlass Supreme

2220 Pontiac Grand Prix

1860 Cadillac Sedan C 113.8

1903 Cadillac Sedan

1861 Saturn coupe

2402 Saturn SC coupe

82

0 0

0 0

0 0

K108

0

0

0

0

0

505

0

505

0

505

0

0

0

0

0

0

505

505

505

0

0

0

0

0

0

505

505

505

505

0

0

0

0

505

505

505

505

505

1000

1000

1000

1000

505

505

505

505

505

1000

1000

1000

1000

1000

1000

505

505

505

1000

1000

1000

1000

1000

505

505

505

1000

1010

1000

1000

1505

1505

1505

1010

1505

1505

1505

1505

1505

1010

1505

1505

0

505

505

505

0

505

505

505

1000

505

505

505

505

1000

1000

505

505

505

505

1000

404

505

505

505

505

1000

404

1404

505

505

505

505

1000

1010

404

1404

1505

505

1505

1010

1404

1010

1010

1010

1010

1010

1010
Car Group

Make/Model

Valid Occupant Protection Codes

85 86 87 88 89 90 91 92 93 94 95

1862 Saturn sedan

2401 Saturn SL sedan

2403 Saturn SW wagon

404 404 404 1404 1010

1404 1404

404 1404 1010

1404

1863 Cadillac Seville 111

1914 Cadillac Seville

1864 Cadillac DeVilleK

1903 Cadillac DeVille

1865 GM Aurora/Riviera G 113.8

1805 Buick Riviera

2122 Oldsmobile Aurora

1866 GM Cavalier/Sunfire J 104.1

2016 Chevrolet Cavalier

2216 Pontiac Sunfire

3004 VW Front engine cars 94.5

3038 VW Scirocco

3042 VW Cabriolet

3005 VW Quantum

3041 VW Quantum

3006 VW Jetta 97.3

3040 VW Jetta

3042 VW Golf/GTI/Cabrio

3045 VW Corrado

3007 VW Fox

3044 VW Fox

0

0

0

0

0

707

0

707

0

707

0

707

0

707

0

707

1000 1010 1010 1010

1010 1010

1010

1010

1010

1010

0 1000 1000 1000 1000

606 606 606 606 606 1010

1010 1010

606 606 606 606 606 404

1010 1010

404 404 404 404 404 404

0 0 0 0 606 606 606

606

3008 VW Passat

3046 VW Passat

3204 Audi 4000

3234 Audi 4000

3205 Audi 5000 105.8

3235 Audi 5000

3237 Audi 100/200

3240 Audi A6

3242 Audi S6

3206 Audi 80/90 100.2

3236 Audi 80/90

3207 Audi 90 102.8

3236 Audi 90

404 404 404 404 404 404

0 1000 1000 1000 1010 1010

1000 1010

1010

1010

0 1000 1000 1000

1000? 1010 1010

1010?

83
Car Group

Make/Model

Valid Occupant Protection Codes

85 86 87 88 89 90 91 92 93 94 95

3208 Audi Cabriolet

3241 Audi Cabriolet

3406 BMW 500 103.8

3435 BMW 500

3407 BM W 300 101

3434 BM W 300

3408 BM W 600

3436 BM W 600

1010 1010

0 0 0 0

0 0 0 0 0 1000 1000 1000 1000

0 0 0 1000 1000

3409 BMW 700 110

3437 BMW 700 0 0

3410 BM W 700 111.5

3437 BM W 700

3411 BM W 700L 116

3437 BM W 700L

0 1000 1000 1000 1000 1000 1010 1010

1000

1000 1000 1000 1000 1000 1010 1010

3412 BM W 500 108.7

3435 BM W 500 0 1000 1000 1000 1000 1000 1010

1000 1010

3413 BM W 850

3438 BM W 850 1000 1000 1010 1010 1010

3414 BM W 300 106.3

3434 BM W 300 1000 1000 1010 1010

3415 BM W 740i 115.4

3437 BM W 740i 1010

3416BMW700iL120.9

3437 BMW 700iL 1010

3514 Nissan 280-300ZX 91.3

3534 Nissan 300ZX 0 0 0 0

3515 Nissan 280-300ZX 2+2 99.2

3534 Nissan 300ZX 2+2

3534 Nissan 300ZX

3518 Nissan Sentra 94.5

3543 Nissan Sentra

0 0 0 0

0 0

3519 Nissan Stanza 97.2

3542 Nissan Stanza

3520 Nissan Pulsar 95

3544 Nissan Pulsar

3521 Nissan 200SX 95.5

3532 Nissan 200SX

0 0

0 0

0 0 0 0

84
Car Group

Make/Model

Valid Occupant Protection Codes

85 86 87 88 89 90 91 92 93 94 95

3522 Nissan Maxima/Stanza 100.4

3539 Nissan Maxima

3542 Nissan Stanza sedan

3542 Nissan Stanza

5833 Infiniti G20

3523 Nissan Stanza wagon 99

3542 Nissan Stanza wagon

3524 Nissan Sentra/Pulsar 95.7

3543 Nissan Sentra

3544 Nissan Pulsar

3546 Nissan NX

3525 Nissan Maxima 104.3

3539 Nissan Maxima

3526 Nissan 240SX 97.4

3532 Nissan 240SX

3527 Nissan 300ZX 96.5

3534 Nissan 300ZX

3528 Nissan 300ZX 2+2 101.2

3534 Nissan 300ZX 2+2

3529 Infiniti M30

5831 Infiniti M30

3530 Infiniti Q45

5832 Infiniti Q45

3531 Nissan Axxess

3548 Nissan Axxess

3532 Nissan Altima

3547 Nissan Altima

3533 Infiniti J30

5834 Infiniti J30

3534 Nissan Maxima 106.3

3539 Nissan Maxima

3535 Nissan 240SX 99.4

3532 Nissan 240SX

0 0 0 404

404

0 0 0

404 404 404 .. .

404 404 404 1010 1010

1010

0 0

0 0 0 404 404 404 404 404 1010

404 505 505 505 505 505

1404 1404

1505 1505

0 0 0 404

1000

1000 1000 1505

404 404 404 404 404 1404

1404 1404

404 404 404 404 404 505

505

505 505 1505 1505 1010 1010

1505

505 505 1505 1505 1010 1010

1505

1000 1000 1505

1000 1000 1505 1505 1010 1010

404 404

1404 1010 1010

1010 1010 1010

1010

1010

85
Valid Occupant Protection Codes

Car Group

Make/Model 85 86 87 88 89 90 91 92 93 94 95

3707 Honda/Acura 96.5

3731 Honda Civic sedan/SW 0 0 0

3732 Honda Accord 0 ......... .

3733 Honda Prelude 0 0 0

5431 Acura Integra 3 door .0000..... .

3708 Honda CRX 86.6

3735 Honda CRX 0 0 0

3709 Honda Civic 93.7

3731 Honda Civic 0 0 0

3710 Honda Accord 102.4

3732 Honda Accord .000 0

505 505 505

5431 Acura Integra sedan . . . . . 404 404 404 404

3711 Acura Legend sedan 108.6

5432 Acura Legend sedan . 0 0 0 1000 1000 .

1000 1000

6131 Sterling . 0 0 0 404 404

404 404 404

3712 Acura Integra 99.2

5431 Acura Integra 5 door .0000..... .

3713 Acura Legend coupe 106.5

5432 Acura Legend coupe . . 0 0 1000 1000

3714 Honda CRX 90.6

3735 Honda CRX . . 0 0 505 505 1000

505

3715 Honda Civic 98.4

3731 Honda Civic . . 0 0 404 404

505 505

3716 Honda Prelude 101

3733 Honda Prelude . . .50 5 505 505 505 ... .

3717 Prelude/Integra 2HB 100.4

3733 Honda Prelude ...... . 1000 1000 1010 1010

1010 1010

5431 Acura Integra 2HB 404 404 404 404

3718 Honda Accord 107.1

3732 Honda Accord 404 404 1000 1000

1000 1010

3719 Acura NSX

5433AcuraNSX ..... . 1000 1000 1010 1010 1010

3720 Acura Legend coupe 111.4

5432 Acura Legend coupe 1000 1000 1010 1010 1010

1010 1010

86
Valid Occupant Protection Codes

Car Group

Make/Model 85 86 87 88 89 90 91 92 93 94 95

3721 Acura Legend sedan 114.6

5432 Acura Legend sedan ..... . 1000 1000 1010 1010 1010

1010 1010

3722 Honda Civic 2HB 101.3

3731 Honda Civic 2HB 1000 1000 1010 1010

5431 Acura Integra 2HB ........ . 1010 1010

3723 Honda Civic sedan 103.2

3731 Honda Civic sedan 1000 1000 1010 1010

5431 Acura Integra sedan ........ . 1010 1010

3724 Acura Vigor

5434 Acura Vigor 1000 1000 1010

1010

3725 Honda Civic del Sol

3735 Honda Civic del Sol 1000 1010 1010

1010

3726 Honda Accord 106.9

3732 Honda Accord 1010 1010

3801 Isuzul-Mark 94.3

3831IsuzuI-Mark 0

3802 Isuzu Impulse

3832 Isuzu Impulse 0 0 0 303 303

3803 Chevrolet Spectrum

2031 Chevrolet Spectrum 0 0 0 0 0 ..... .

3831 Isuzul-Mark .000 0

3804 Geo Storm

2035 Geo Storm .... . 1000 1000 1000 1000

3832 Isuzu Impulse .... . 1000 1000 1000

3833 Isuzu Stylus .... . 1000 1000 1000 1000

3903 Jaguar XJ Sedan 113

3932 Jaguar XJ sedan 0 0 0 0 404 404 404 404 1000 1000 1010

1010

3904 Jaguar XJ-S coupe

3931 Jaguar XJ-S 0 0 0 0 0 404 1000 1000 1000 1010 1010

404 404 1000

4107 Mazda RX-7 95.3

4134MazdaRX-7 0

4109 Mazda GLC 93.1

4135 Mazda GLC 0

4110 Mazda 626 98.8 FWD

4137 Mazda 626 0 0 0

404

87
Valid Occupant Protection Codes

Car Group

Make/Model 85 86 87 88 89 90 91 92 93 94 95

4111 Mazda 323/Tracer

1436 Mercury Tracer . . 0 0 303

4135 Mazda 323 .000 0

4112 Mazda RX-7 95.7

4134MazdaRX-7 . 0 0 0 0 404 404

404 1000 1000

4113 Mazda 626 101.4

4137 Mazda 626 . . . 0 404 404 404 404

404

4114 Mazda 929 106.7

4143 Mazda 929 . . 0 0 404 404

4115 Ford Probe 99

1218 Ford Probe . . . 0 303 303 303 .

4144MazdaMX6 . . 0 0 404 404 404 .

404 404

4116Mazda323HB96.S

4135 Mazda 323 404 404 404 404 404

4117 Ford Escort 98.4

1213 Ford Escort 303 303 303 303 1303 1313

1436 Mercury Tracer 303 303 303 1303 1313

4135 Mazda 323 Protege 404 404 404 404 404

4118MazdaMiata

4145 Mazda Miata 1000 1000 1000 1000 1010 1010

4119 Mazda MX3

4146 Mazda MX3 404 404 1010 1010

4120 Mazda 929 112.2

4143 Mazda 929 1010 1010 1010 1010

4121 Mazda 626/Probe 102.9

1218 Ford Probe 1000 1010 1010

4137 Mazda 626 1000 1010 1010

4144 Mazda MX6 1000 1010 1010

4122 Mazda RX7 95.5

4134 Mazda RX7 1000 1010 1010

4123 Mazda Protege 102.6

4135 Mazda Protege 1010

4124 Mazda Millenia

4147 Mazda Millenia 1010

4204 Mercedes SL roadster 96.9

4233 Mercedes 380SL 0

4208 Mercedes basic sedan 110

4231 Mercedes basic sedan 0 ......... .

88
Valid Occupant Protection Codes

Car Group

Make/Model 85 86 87 88 89 90 91 92 93 94 95

4209 Mercedes basic C coupe 106.7

4231 Mercedes basic coupe 0 ......... .

4210 Mercedes S (super) sedan 115.6

4237 Mercedes SD/SE 0 1000 1000 1000 1000 1000 1000

1000 1010 1010 1010

4211 Mercedes SEL (long super) sedan 121.1

4236 Mercedes SDL/SEL 0 1000 1000 1000 1000 1000 1010

1000 1010 1010

4212 Mercedes SEC coupe 112.2

4236 Mercedes SEC 0 1000 1000 1000 1000 1000 1010 ... .

1000 1010 1010

4213 Mercedes 190

4239 Mercedes 190 0 1000 1000 1000 1000 1000 1000 1000 1000

1000 1010 1010 1010 1010

4214 Mercedes basic E sedan 110.2

4231 Mercedes basic sedan . 1000 1000 1000 1000 1000 1000 1000 1010

1010 1010 1010 1010

4231 Mercedes E sedan 1010 1010

4215 Mercedes SL roadster 96.7

4233 Mercedes 560SL . 1000 1000 1000 1000

4216 Mercedes basic E coupe 106.9

4231 Mercedes basic coupe . . .100 0 1000 1000 1000 1000 1010

1010 1010 1010 1010

4231 Mercedes E coupe

4217 Mercedes SL roadster 99

4233 Mercedes 300SL/500SL

4233 Mercedes SL roadster

4218 Mercedes S sedan 119.7

4236 Mercedes SEC coupe

4237 Mercedes SE/SD . . .

4237 Mercedes S320/S350 sedan

4219 Mercedes long S sedan 123.6

4236 Mercedes SEL sedan

4236 Mercedes S420/S500/S600 sedan

4220 Mercedes C sedan

4242 Mercedes C sedan

4221 Mercedes S coupe 115.9

4236 Mercedes S coupe

4406 Peugeot 505 sedan

4434 Peugeot 505 sedan 0 0 0

4407 Peugeot 505 wagon

4434 Peugeot 505 wagon 0 0 0

89

0

606

0

606

0

606

0

606

1000

1010

404

606

404

606

1010

404

606

404

606

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010
Car Group

Make/Model

4408 Peugeot 405

4436 Peugeot 405

4501 Porsche 911

4531 Porsche 911

4503 Porsche 924/944

4534 Porsche 924

4537 Porsche 944

4539 Porsche 968

4504 Porsche 928

4535 Porsche 928

4505 Porsche

4540 Porsche

4605 Renault 18/Fuego

4637 Renault R18i

4638 Renault Fuego

4606 Renault Alliance

4639 Renault Alliance

4640 Renault Encore

4607 Renault Medallion sedan

4644 Renault Medallion sedan

4608 Renault Medallion wagon

4644 Renault Medallion wagon

4609 Eagle Premier

740 Dodge Monaco

1040 Eagle Premier

4704 Saab 900 99.4

4731 Saab 900

4705 Saab 9000

4734 Saab 9000

4706 Saab 900 102.4

4731 Saab 900

Valid Occupant Protection Codes

85 86 87 88 89 90 91 92 93 94 95

0 404 404

404 606 606

606

0 0 0 0 0 1010 1010

0 0 0 0 .

0 0 0 0 0 1010 1010

1010 1010 1010

0 0 0 0 0 1010 1010

1010

1010

1010

1010 1010 1010

0

0

0

0

0

0

0

0

505

0

0

404

404

404 404 404

0 o 404 404 404

404 404

0 0 0 0 0 1000 1000 1000 1000 1000

404 404 404

0 0 0 0 0 1000 1000 1000 1000 1010 1010

1000 1000

1010 1010

90
Valid Occupant Protection Codes

Car Group

Make/Model 85 86 87 88 89 90 91 92 93 94 95

4806 Subaru sedan 97

4831 Subaru sedan 0 0 0 0 0 0 404 .

404 404 9

404

4831 Subaru Loyale . . . . . . . 404 404 404

4835 Subaru XT 0 0 0 404 404 404 404 .

404

4807 Subaru hatchback 93

4831 Subaru hatchback 0 0 0 0 0 ..... .

4808 Subaru Justy

4836 Subaru Justy . . 0 0 0 505 505 505 505 505

4809 Subaru Legacy 101.6

4834 Subaru Legacy . . . . . 404 404 404 1404 1404 .

1404

4810 Subaru SVX

4837 Subaru SVX 1404 1404 1010 1010

4811 Subaru Impreza

4838 Subaru Impreza . . . . . . . . 1000 1000 1010

1010

4812 Subaru Legacy 103.5

4834 Subaru Legacy ......... . 1010

4911 Toyota Celica 98.4

4933 Toyota Celica 0 0 ........ .

4912 Toyota Cressida 104.1

4935 Toyota Cressida 303 ......... .

4916 Toyota Corolla 94.5

4932 Toyota Corolla 2 door 0 0 0 .. .

4918 Toyota Supra 103

4934 Toyota Supra 0 0 ........ .

4919 Toyota Tercel/Corolla 95.7

2032 Chevrolet Nova . 0000...... .

2032GeoPrizm ... . 0 0 606 606 .. .

606 606

4932 Toyota Corolla 4 dr 0 0 0 0 0 606 606 606 .

4932 Toyota Corolla FX-16 ..000..... .

4932 Toyota Corolla 2 dr . . 0 0 606 606 606 .

4938 Toyota Tercel 0 0 ........ .

4938 Toyota Tercel wagon 0 0 0 ....... .

4920 Toyota Camry 102.4

4940 Toyota Camry 0 0 303 303 303 303 303 .

5731 Lexus ES-250 .... . 1000 1000 .

4921 Toyota MR-2 91.3

4941 Toyota MR-2 . 00000. . ... .

91
Valid Occupant Protection Codes

Car Group

Make/Model 85 86 87 88 89 90 91 92 93 94 95

4922 Toyota Cressida 104.5

4935 Toyota Cressida . 303 303 303 303 303 303 303 .

4923 Toyota Supra 102.2

4934 Toyota Supra . 0 0 0 0 1000 1000 1000

4924 Toyota Celica 99.4

4933 Toyota Celica . . 0 0 0 1000 1000 1000 1000

4925 Toyota Tercel 93.7

4938 Toyota Tercel . 0 0 0 606 606 606 606 1006 1010

4942 Toyota Paseo 606 606 1006 1006

4926 Lexus LS^lOO 110.8

5932 Lexus LS-400 1000 1000 1000 1010 1010

4927 ToyotaMR-2 94.5

4941 Toyota MR-2 1000 1000 1000 1010 1010

4928 Toyota Camry 103.1

4940 Toyota Camry 1000 1000 1010 1010

5931 Lexus ES-300 1000 1000 1010 1010

4929 Lexus SC-300/400

5933 Lexus SC-300/400 1000 1010 1010 1010

4930 Toyota Corolla 97

2032GeoPrizm 1000 1010 1010

4932 Toyota Corolla 1000 1010 1010

4931 Toyota Supra 100.4

4934 Toyota Supra 1000 1010 1010

4932 Lexus GS-300

5934 Lexus GS-300 1010 1010 1010

4933 Toyota Celica 99.9

4933 Toyota Celica 1010 1010

4934 Lexus LS^OO 112.2

5932 Lexus LS^OO 1010

4935 Toyota Avalon

4943 Toyota Avalon 1010

5104 Volvo 240

5134 Volvo 240 0 0 0 0 0 1000 1000 1000 1000

5105 Volvo 740/760

5138 Volvo 760/780 0 0 0 1000 1000 1000 1000 ... .

1000

5139 Volvo 740 0 0 0 0 0 1000 1000 1000

1000 1000 1000

5140 Volvo 940 ..... . 1000 1000 1000 1010 1010

5141 Volvo 960 ..... . 1000 1000 1010 1010 1010

5106 Volvo 850

5142 Volvo 850 ....... . 1010 1010 1010

92
Valid Occupant Protection Codes

Car Group

Make/Model 85 86 87 88 89 90 91 92 93 94 95

5204 Colt/Champ 90.6

734 Dodge Colt 2 door

934 Plymouth Colt 2 door

5205 Hyundai Excel 93.7

734 Dodge Colt 4 door

734 Dodge Colt 2 door

734 Dodge Colt DL wagon

934 Plymouth Colt 4 door

934 Plymouth Colt 2 door

934 Plymouth Colt DL wagon

5235 Mitsubishi Mirage

5236 Mitsubishi Precis

5532 Hyundai Excel

5206 Mitsubishi Starion

635 Chrysler Conquest

735 Dodge Conquest

935 Plymouth Conquest

5231 Mitsubishi Starion

5207 Mitsubishi Tredia/Cordia

5232 Mitsubishi Tredia

5233 Mitsubishi Cordia

5208 Colt Vista

744 Dodge Colt Vista

944 Plymouth Colt Vista

5209 Mitsubishi Galant 102.4

5234 Mitsubishi Galant

5238 Mitsubishi Sigma

5210 Mitsubishi Mirage 96.7

1034 Eagle Summit sedan

5235 Mitsubishi Mirage sedan

5235 Mitsubishi Mirage hatchback

5211 Dodge Colt 93.9

734 Dodge Colt 2HB

934 Plymouth Colt 2HB

5235 Mitsubishi Mirage 2HB

5212 Mitsubishi Eclipse 97.2

937 Plymouth Laser .... . 404 404 404 404 404

1037 Eagle Talon .... . 404 404 404 404 404

5237 Mitsubishi Eclipse .... . 404 404 404 404 404

5213 Dodge Stealth

739 Dodge Stealth 1000 1000 1000 1010 1010

5239 Mitsubishi 3000GT ..... . 1000 1000 1000 1010 1010

93

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

707

0

707

404

404

0

0

0

0

0

0

0

0

0

0

0

707

0

707

404

404

0

0

0

0

0

0

0

0

707

0

707

404

404

0

0

0

0

404

404

404

404

404

404

404

404

404

404

1000

404

404

404

404

404

404

404

404

1000

404

404

404

404

404

404

404

404

404

404

404

404
Valid Occupant Protection Codes

Car Group

Make/Model 85 86 87 88 89 90 91 92 93 94 95

5214 Mitsubishi LRV

744 Dodge Colt Vista ...... .

944 Plymouth Colt Vista ...... .

1044 Eagle Summit wagon ...... .

5244 Mitsubishi LRV

5215 Mitsubishi Diamante

5240 Mitsubishi Diamante ...... .

5245 Mitsubishi Expo SP ...... .

5216 Dodge Colt 2 door 96.1

734 Dodge Colt 2 door ...... .

934 Plymouth Colt 2 door ...... .

1034 Eagle Summit 2 door ...... .

5235 Mitsubishi Mirage 2 door ...... .

5217 Dodge Colt 4 door 98.4

734 Dodge Colt 4 door ...... .

934 Plymouth Colt 4 door ...... .

1034 Eagle Summit 4 door ...... .

5235 Mitsubishi Mirage 4 door . . . . . . .

5218 Mitsubishi Galant 103.7

643 Chrysler Sebring ...... .

742 Dodge Avenger ...... .

5234 Mitsubishi Galant ...... .

5219 Mitsubishi Eclipse 98.8

1037 Eagle Talon ...... .

5237 Mitsubishi Eclipse ...... .

5301 Chevrolet Sprint 88.4

2033 Chevrolet Sprint 4 door 0 0 ........ .

2033 Chevrolet Sprint 2 door 0 0 0 0 ...... .

5302 Chevrolet Sprint 92.3

2033 Chevrolet Sprint 4 door ..00...... .

5303 Geo Metro 89.2

2034 Geo Metro 2 door . . . 0 505 505 505 505 505

1000 1000 1000 1000

5334 Suzuki Swift 2 door . . . 0 505 505 505 505 505

5304 Geo Metro 93.1

2034 Geo Metro 4 door . . . 0 505 505 505 505 505

2034 Geo Metro 1010

5334 Suzuki Swift 4 door . . . 0 505 505 505 505 505

5334 Suzuki Swift 1010

5501 Hyundai Sonata 104.3

5533 Hyundai Sonata . . . 0 404 404 404 404 404

707 1010

5502 Hyundai Excel 93.8

5236 Mitsubishi Precis .... . 606 606 606 606 606

5532 Hyundai Excel .... . 606 606 606 606 606

5534 Hyundai Scoupe ..... . 606 606 606 606 606

94

404

404

404

404

1000

404

404

404

404

404

1000

404

404

404

404

404

404

404

404

404

1004

1004

1004

1004

1010

1004

1004

1004

1004

1004

1004

1004

1004

1004

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010

1010
Valid Occupant Protection Codes

Car Group

Make/Model 85 86 87 88 89 90 91 92 93 94 95

5503 Hyundai Elantra

5535 Hyundai Elantra 606 606 1006 1006

5504 Hyundai Accent

5536 Hyundai Accent 1010

5505 Hyundai Sonata 106.3

5533 Hyundai Sonata 1010

5603MerkurXR4Ti

5631MerkurXR4Ti 0 0 0 0 0

5604 Merkur Scorpio

5632 Merkur Scorpio . . 0 0 303

5701 Yugo

5731 Yugo . 0 0 0 0 606 606

707 707

6001 Daihatsu Charade

6031 Daihatsu Charade . . . 0 0 404 404 404

606 606 606 606 606

6301 Pontiac LeMans (Daewoo)

2231 Pontiac LeMans . . 0 0 404 404 404 404

6401 Ford Festiva

1234 Ford Festiva . . 0 0 303 303 303 303

6402 Kia Sephia

6431KiaSephia 303 303 303

6403 Ford Aspire 2dr 90.7

1236 Ford Aspire 2dr ........ . 1010 1010

6404 Ford Aspire 4dr 93.9

1236 Ford Aspire 4dr ........ . 1010 1010

6501 Mercury Capri XR-2

1431 Mercury Capri . . . 0 303 1000 1000 1000 1010

95

APPENDIX B

LIGHT TRUCKS

TYPES OF OCCUPANT PROTECTION BY MAKE-MODEL AND YEAR

EXPLANATION OF CODES

trucks of this group or make-model were not sold in this model year

0 manual 3-point belts for driver and right-front (RF) passenger

9 occupant protection system unknown - or - 2 or more types offered that year,

but VIN does not specify which type is on a particular vehicle

1000 driver air bag + manual 3-point belts for driver and RF

1010 dual air bags + manual 3 -point belts for driver and RF

Note. If two types of occupant protection were offered in the same year, and the VIN can be used

to identify which type is on a particular vehicle, the first type is shown on the first line, and the second

type on the second line. Codes marked with a "?" are not used in the analyses. Pre-1991 light trucks

are equipped with manual 3-point belts for driver and RF (code 0).

97
Valid Occupant Protection Codes

Light Truck Group

Make/Model

7005 Jeep Cherokee

7006 Jeep Wagonecr

7007 Jeep Grand Wagoneer

7010 Jeep Wrangler

7011 JeepComanche 113/119.9

7102 Dodge DAV 150 Pickup

7103 Dodge DAV 250/350 Pickup

7105 Dodge Ramcharger

7106 Dodge Ram Van 109.6/127.6

7107 Dodge Ram Van 127.6

7108 Dodge Dakota 111.9/123.9

7110 Dodge DAV Club Cab Pickup 149

7111 Dodge Dakota Club Cab 131

7112 Caravan/Voyager 112.3

7113 Grand Caravan/Voyager/Town-Country 119.3

7114 Jeep Grand Cherokee

7017 Jeep Grand Cherokee

7018 Jeep Grand Cherokee 4x4

7019 Jeep Grand Wagoneer 4x4

7115 Dodge Ram 1500 Pickup

7116 Dodge Ram 2500/3500 Pickup

7117 Dodge Ram Club Cab Pickup

7401 Ford Ranger 107.9/113.9

7402 Ford Fl 50 Pickup

7403 Ford F250/350 Pickup

7404 Ford Fl 50 Supercab Pickup

7405 Ford F250/350 Supercab Pickup

7407 Ford Bronco

7409 Ford van 138

7410 Ford Ranger Supercab

7411 Ford Aerostar

91

0

0

0

0

0

0

0

0

0

0

0

0

0

9

9

0

0

0

0

0

0

0

0

0

92

0

0

0

0

0

0

0

0

0

0

0

0

0

1000

1000

0

0

0

0

0

0

0

1000

93

0

0

0

0

0

0

0

0

0

0

1000

1000

1000

1000

1000

0

0

0

0

0

1000

94

0

0

1000?

1000?

0

0

0

1000

1000

1000

1010

1010

1000

1000

1000

1000

1000

1000

1000

0

0

1000

1000

95

1000

0

1000

1000

1000

1000

1010

1010

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

1000

98
Light Truck Group

Make/Model

7412 Ford F350 Crew Cab Pickup 168.4

7413 Ford Explorer 2dr 102.1

7440 Ford Explorer 2dr

7441 Ford Explorer 2dr 4x4

8310 Mazda Navajo 4x4

8311 Mazda Navajo

7414 Ford Explorer 4dr 111.9

7415 Ford van 138 (92 redesign)

7416 Ford Ranger 108.0/114.0

7452 Ford Ranger

7453 Ford Ranger 4x4

8310 Mazda B pickup

8311 Mazda B pickup 4x4

7417 Ford Ranger Supercab (1993 redesign)

7454 Ford Ranger Supercab

7455 Ford Ranger Supercab 4x4

8312 Mazda B cab-plus pickup

8313 Mazda B cab-plus pickup 4x4

7418 Mercury Villager/Nissan Quest

7419 Ford Windstar

7604 GM S Blazer/Jimmy 2dr 100.5

7605 GM K/V Blazer/Jimmy 106.5

7606 GM C/K/R/V 10 Suburban 129.5

7607 GM C/K/R/V 20 Suburban 129.5

7608 GM Astro/Safari van

7609 GM full-sized van 110/125

7610 GM full-sized van 125

7621 Chevrolet G20 Sportvan

7622 Chevrolet G30 Chevy Van

7623 Chevrolet G30 Sportvan

7721 GMC 2500 Rally

7722 GMC 3500 Vandura

7723 GMC 3500 Rally

7612 GM C/K/R/V 20/30 4 dr pickup 164.5

7613 GMS/T pickup 108.3/117.9

7614 GM S/T Maxicab pickup

Valid Occupant Protection Codes

91 92 93 94 95

0 0 0 0 0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1000

0

0

0

0

0

0

0

1000

0

0

0

0

9

1000

1000

1000

9

9

1000

1000

9

9

9

1010

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1000

1000

1000

0

1000

0

1000

1000

0

1000

0

1000

0

0

0

1000

1000

1000

0

1000

0

1000

1000

0

1000

0

1000

1000

1000

99
Light Truck Group

Make/Model

7615 GMC/K 1500 pickup 117.5/131.5

7616 GM C/K 2500/3500 pickup 131.5

7617 GM C/K extended-cab pickup 155.5

7618 GM extended van 146

7619 GMLumina APV/Silhouette/Trans Sport

7620 GM C/K extended-cab pickup 141.5/155.5

7621 GMS Blazer/Jimmy 4dr 107.0

7657 Chevrolet S10 Blazer 4dr

7658 Chevrolet S10 4x4 Blazer 4dr

7757 GMCS15 Jimmy 4dr

7758 GMC SI 5 4x4 Jimmy 4dr

7802 Oldsmobile Bravada 4x4

7622 GM C/K3500 Crew Cab pickup 168.5

7623 GM Tahoe/Yukon 111.5

7662 Chevrolet K1500 4x4 Blazer

7662 Chevrolet 4x4 Tahoe

7762 GMC 4x4 Yukon

7624 GM C/K 1500 Suburban 131.5

7625 GM C/K 2500 Suburban 131.5

8001 VW Vanagon

8103 Nissan pickup 104.3

8104 Nissan pickup 116.1

8105 Nissan Pathfinder

8203 Isuzu Trooper II 104.3

8204 Isuzu PUP 105.6

8205 Isuzu PUP 119.2

8206 Isuzu Amigo

8208 Isuzu Rodeo

8209 Isuzu Trooper 4dr 108.7

8102 Isuzu Trooper 2dr 91.7

8211 Honda Passport

8301 Mazda pickup 108.7

8302 Mazda pickup 117.5

Valid Occupant Protection Codes

91

0

0

0

0

0

0

0

0

0

0

0

92

0

0

0

0

0

0

o o o o o

93

0

0

0

0

0

0

o o o o o

94

0

0

0

0

1000

1000

0

0

0

0

0

0

95

1000

1000

1000

0

1000

1000

1000

1000

1000

1000

1000

1000?

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1000?

0?

1000

1000

0

0

0

0

0

0

0

1010

1010

0

100
Valid Occupant Protection Codes

Light Truck Group

Make/Model

8303 Mazda MPV

8501 Toyota pickup 103

8502 Toyota pickup 112.2

8503 Toyota 4Runner

8506 Toyota pickup 121.5

8507 Toyota Land Cruiser 112.2

8508 Toyota Previa

8509 Toyota T100 pickup

8602 Mitsubishi Montero 2dr 92.5

8603 Mitsubishi Mighty Max pickup 105

8604 Mitsubishi Mighty Max pickup 116

8606 Mitsubishi Montero 4dr 106.1

8607 Mitsubishi Montero 4dr 107.3

8701 Suzuki Samurai

8702 Suzuki Sidekick/Tracker 2dr 86.6

8703 Suzuki Sidekick 4dr 97.6

8801 Daihatsu Rocky

9001 Kia Spoilage

91

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

92

0

0

0

0

0

0

1000

0

0

0

0

0

0

0

93

1000

0

0

0

0

0

1000

0

0

0

0

0

0

0

94

1000

0

0

0

0

0

1010

1000

0

0

1000

0

0

0

95

1000

0

0

0

0

0

1010

1000

0

1000

0

0

0

0

101

APPENDIX C

SUPPLEMENTARY TABLES

DETAILED ANALYSES OF FATALITY REDUCTION

103
TABLE C-l - CARS UP TO 2778 POUNDS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

(both seats occupied; make-models that had manual or automatic

3-point belts and added driver air bags without changing the belt system)

Driver

Fatalities

Right Front

Fatalities

Risk

Ratio

Percent

Reduction

Cars with belts only

Cars w. driver air bags

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

268 291 .921

114 171 .667

(statistically significant difference: xz = 4.81)

28

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only

Cars w. driver air bags

239 269 .888

126 133 .947

(not a statistically significant difference: x

2 = 0.18)

-7

Cars with belts only

Cars w. driver air bags

IN ALL CRASHES

848 923 .919

457 536 .853

(not a statistically significant difference: x

 2

 = 0.88)

104
TABLE C-2 - CARS 2779-3119 POUNDS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

(both seats occupied; make-models that had manual or automatic

3-point belts and added driver air bags without changing the belt system)

Driver

Fatalities

Right Front

Fatalities

Risk

Ratio

Percent

Reduction

Cars with belts only

Cars w. driver air bags

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

236 259 .911

112 177 .633

(statistically significant difference: %2 = 5.89)

31

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only

Cars w. driver air bags

233 229 1.017

144 147 .980

(not a statistically significant difference: x

2 = 0.06)

Cars with belts only

Cars w. driver air bags

IN ALL CRASHES

778 847 .919

452 540 .837

(not a statistically significant difference: x

2

 = 1-32)

105
TABLE C-3 - CARS OVER 3119 POUNDS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

(both seats occupied; make-models that had manual or automatic

3-point belts and added driver air bags without changing the belt system)

Driver

Fatalities

Right Front

Fatalities

Risk

Ratio

Percent

Reduction

Cars with belts only

Cars w. driver air bags

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

321 317 1.013

87 150 .580

(statistically significant difference: x

2

 = 12.85)

43

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only

Cars w. driver air bags

226 244 .926

120 128 .938

(not a statistically significant difference: %2 = 0.01)

-1

Cars with belts only

Cars w. driver air bags

IN ALL CRASHES

890 945 .942

404 491 .823

(not a statistically significant difference: %2 = 2.73)

13

106
TABLE C-4 - CARS UP TO 2778 POUNDS, BY IMPACT LOCATION.

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 847 539

Purely frontal fatalities 907 396 31

(statistically significant difference: x2 = 21.38)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 847 539

Partially frontal fatalities 650 363 12

(not a statistically significant difference: %2 - 2.33)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 847 539

Frontal fatalities 1557 759 23

(statistically significant difference: x2 = 14.25)

Fatality reduction for driver air bags in all types of crashes: 15 percent

107
TABLE C-5- CARS 2779-3119 POUNDS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 617 381

Purely frontal fatalities 603 311 16

(not a statistically significant difference: x

2 = 3 55)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 617 381

Partially frontal fatalities 549 317

(not a statistically significant difference. x

2 = 0.49)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 617 381

Frontal fatalities 1152 628 12

(not a statistically significant difference: x

2

 ~ 2.32)

Fatality reduction for driver air bags in all types of crashes: 8 percent

108
TABLE C-6 - CARS OVER 3119 POUNDS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 377 201

Purely frontal fatalities 395 140 34

(statistically significant difference: %1 = 9.69)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 377 201

Partially frontal fatalities 318 164

(not a statistically significant difference: %2 = 0.06)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 377 201

Frontal fatalities 713 304 20

(not a statistically significant difference: %2 = 2.41)

Fatality reduction for driver air bags in all types of crashes: 13 percent

109
TABLE C-7 - SINGLE-VEHICLE CRASHES, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

(both seats occupied; make-models that had manual or automatic

3-point belts and added driver air bags without changing the belt system)

Driver

Fatalities

Right Front

Fatalities

Risk

Ratio

Percent

Reduction

Cars with belts only

Cars w. driver air bags

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

266 280 .950

117 158 .741

(not a statistically significant difference: %2 - 2.80)

22

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only

Cars w. driver air bags

363 395 .918

216 221 .977

(not a statistically significant difference: x

2

 = 0.26)

-6

Cars with belts only

Cars w. driver air bags

IN ALL CRASHES

1080 1115 .968

602 648 .929

(not a statistically significant difference: %2 = 0.35)

110
TABLE C-8 - MULTIVEHICLE CRASHES, BY IMPACT LOCATION.

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

(both seats occupied; make-models that had manual or automatic

3-point belts and added driver air bags without changing the belt system)

Driver

Fatalities

Right Front

Fatalities

Risk

Ratio

Percent

Reduction

Cars with belts only

Cars w. driver air bags

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

559 587 .952

196 340 .576

(statistically significant difference: x2 = 22.01)

39

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only

Cars w. driver air bags

335 347 .965

174 187 .930

(not a statistically significant difference: %2 = 0.08)

Cars with belts only

Cars w. driver air bags

IN ALL CRASHES

1436 1600 .898

711 919 .774

(statistically significant difference: x2 = 5.78)

14

111
TABLE C-9 - SINGLE-VEHICLE CRASHES, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 926 607

Purely frontal fatalities 736 358 26

(statistically significant difference: x1 = 12.97)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 926 607

Partially frontal fatalities 885 511 12

(not a statistically significant difference: x

2 = 2.77)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 926 607

Frontal fatalities 1621 869 18

(statistically significant difference: x2 = 9 -°l)

Fatality reduction for driver air bags in all single-vehicle crashes: 12 percent

112
TABLE C-10- MULTTVEHICLE CRASHES, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 915 514

Purely frontal fatalities 1169 489 26

(statistically significant difference: %2 —14.67)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 915 514

Partially frontal fatalities 632 333

(not a statistically significant difference: x

2

 = 0.54)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 915 514

Frontal fatalities 1801 822 19

(statistically significant difference: x2 = 8.98)

Fatality reduction for driver air bags in all multivehide crashes: 12 percent

113
TABLE C-l 1 - DRIVERS AGE 14-29, BY IMPACT LOCATION.

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

(both seats occupied by people age 14-29; make-models that had manual or automatic

3-point belts and added driver air bags without changing the belt system)

Driver

Fatalities

Right Front

Fatalities

Risk

Ratio

Percent

Reduction

Cars with belts only

Cars w. driver air bags

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

267 247 1.081

98 145 .676

(statistically significant difference: x2 = 8.92)

37

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only

Cars w. driver air bags

284 298 .953

152 165 .921

(not a statistically significant difference: x

2 = 0.36)

Cars with belts only

Cars w. driver air bags

IN ALL CRASHES

930 935 .995

473 550 .860

(statistically significant difference: x2 - 5.91)

14

114
TABLE C-12 - DRIVERS AGE 56 OR OLDER, BY IMPACT LOCATION.

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

(both seats occupied by people age 56+; make-models that had manual or automatic

3-point belts and added driver air bags without changing the belt system)

Driver

Fatalities

Right Front

Fatalities

Risk

Ratio

Percent

Reduction

Cars with belts only

Cars w. driver air bags

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

234 300 .780

95 177 .537

(statistically significant difference: %2 = 5.90)

31

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only

Cars w. driver air bags

150 191 .785

108 124 .871

(not a statistically significant difference: %2 = 0.37)

-11

Cars with belts only

Cars w. driver air bags

IN ALL CRASHES

658 857 .768

360 519 .694

(not a statistically significant difference: x

2 = 1.40)

10

115
TABLE C-13 - DRIVERS AGE 14-29, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 840 505

Purely frontal fatalities 745 328 27

(statistically significant difference: x2 = 12.87)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 840 505

Partially frontal fatalities 692 360 13

(not a statistically significant difference: x

2 = 2.83)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 840 505

Frontal fatalities 1437 688 20

(statistically significant difference: x2 = 9.76)

Fatality reduction for driver air bags in all types of crashes: 13 percent

116
TABLE C-14 - DRIVERS AGE 30-55, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 579 364

Purely frontal fatalities 653 267 35

(statistically significant difference: x2 = 29.08)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 579 364

Partially frontal fatalities 519 283 13

(not a statistically significant difference: %2 = 2.04)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 579 364

Frontal fatalities 1172 550 25

(statistically significant difference: %2 = 12.00)

Fatality reduction for driver air bags in all types of crashes: 17 percent

117
TABLE C-15 - DRIVERS AGE 56 OR OLDER, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 422 252

Purely frontal fatalities 507 252 17

(not a statistically significant difference: x

2 = 2.75)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 422 252

Partially frontal fatalities 306 201 -10

(not a statistically significant difference: x

2

 - 0.62)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 422 252

Frontal fatalities 813 453

(not a statistically significant difference: x

2

 = 0.49)

Fatality reduction for driver air bags in all types of crashes: 4 percent

118
TABLE C-16 - DRIVERS AGE 56-69, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 172 103

Purely frontal fatalities 237 109 23

(not a statistically significant difference: %2 = 2.41)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 172 103

Partially frontal fatalities 131 85 -8

(not a statistically significant difference: x

2

 = 0.18)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 172 103

Frontal fatalities 368 194 12

(not a statistically significant difference: %2 = 0.70)

Fatality reduction for driver air bags in all types of crashes: 8 percent

119
TABLE C-17 - DRIVERS AGE 70 OR OLDER, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-pouit belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 250 149

Purely frontal fatalities 270 143 11

(not a statistically significant difference: %2 = 0.65)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 250 149

Partially frontal fatalities 175 116 -11

(not a statistically significant difference: x

2 = 0.45)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 250 149

Frontal fatalities 445 259

(not a statistically significant difference." z

2 = 0.03)

Fatality reduction for driver air bags in all types of crashes: 2 percent

120
TABLE C-18 - CAR DRIVERS, INCLUDING ALL MAKE-MODELS

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(all 1985-95 cars that had manual or automatic 3-point belts only,

or had driver air bags plus 3-point belts;

including make-models that got ABS at the same time as air bags)

OBSERVED

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 18,098 2180

Purely frontal fatalities 20,061 1611 33

BIAS over analysis with matching make-models and control for ABS: 6 percent

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 18,098 2180

Partially frontal fatalities 14,940 1612 10

BIAS over analysis with matching make-models and control for ABS: 1 percent

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 18,098 2180

Frontal fatalities 35,001 3223 24

BIAS over analysis with matching make-models and control for ABS: 5 percent

Observed fatality reduction for driver air bags in all types of crashes: 16 percent

BIAS over analysis with matching make-models and control for ABS: 4 percent

121
TABLE C-19 - DRIVERS AGE 56-69, INCLUDING ALL MAKE-MODELS

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(all 1985-95 cars that had manual or automatic 3-point belts only,

or had driver air bags plus 3-point belts;

including make-models that got ABS at the same time as air bags)

Frontal Fat. Red.

for Air Bags (%)

Cars with Cars with

Belts Only Driver Air Bags Observed Adjusted

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 1996 263

Purely frontal fatalities 2745 244 33 27

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 1996 263

Partially frontal fatalities 1665 203 7

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 1996 263

Frontal fatalities 4410 447 23 18

Fatality reduction for driver air bags in all types of crashes: 16 12

122
TABLE C-20 - DRIVERS AGE 70 OR OLDER, INCLUDING ALL MAKE-MODELS:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(all 1985-95 cars that had manual or automatic 3-point belts only,

or had driver air bags plus 3-point belts;

including make-models that got ABS at the same time as air bags)

Frontal Fat. Red.

for Air Bags (%)

Cars with Cars with

Belts Only Driver Air Bags Observed Adjusted

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 2996 394

Purely frontal fatalities 3038 331 17 11

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 2996 394

Partially frontal fatalities 2046 280 -4 -5

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 2996 394

Frontal fatalities 5084 611

Fatality reduction for driver air bags in all types of crashes:

123
TABLE C-21 - MALE DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 1180 727

Purely frontal fatalities 1283 569 28

(statistically significant difference: x2 = 22.77)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 1180 727

Partially frontal fatalities 1031 560 12

(not a statistically significant difference: x

2 = 3.19)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 1180 727

Frontal fatalities 2314 1129 21

(statistically significant difference: x2 = 15.40)

Fatality reduction for driver air bags in all types of crashes: 14 percent

124
TABLE C-22 - FEMALE DRIVERS, BY IMPACT LOCATION:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(make-models that had manual or automatic 3-point belts

and added driver air bags without changing the belt system;

excluding make-models that got ABS at the same time as air bags)

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfirontal fatalities 661 394

Purely frontal fatalities 622 278 25

(statistically significant difference: %1 = 8.98)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 661 394

Partially frontal fatalities 486 284

(not a statistically significant difference: %2 = 0.04)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 661 394

Frontal fatalities 1108 562 15

(statistically significant difference: x2 = 3.87)

Fatality reduction for driver air bags in all types of crashes: 9 percent

125
TABLE C-23 - MALE DRIVERS, INCLUDING ALL MAKE-MODELS:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(all 1985-95 cars that had manual or automatic 3-point belts only,

or had driver air bags plus 3-point belts;

including make-models that got ABS at the same time as air bags)

Frontal Fat. Red.

for Air Bags (%)

Cars with Cars with

Belts Only Driver Air Bags Observed Adjusted

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 10,668 1395

Purely frontal fatalities 12,662 1090 34 28

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 10,668 1395

Partially frontal fatalities 9,528 1074 14 13

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 10,668 1395

Frontal fatalities 22,190 2164 25 20

Fatality reduction for driver air bags in all types of crashes: 17 13

126
TABLE C-24- FEMALE DRIVERS, INCLUDING ALL MAKE-MODELS:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

(all 1985-95 cars that had manual or automatic 3-point belts only,

or had driver air bags plus 3-point belts;

including make-models that got ABS at the same time as air bags)

Frontal Fat. Red.

for Air Bags (%)

Cars with Cars with

Belts Only Driver Air Bags Observed Adjusted

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 7,429 785

Purely frontal fatalities 7,399 521 33 27

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 7,429 785

Partially frontal fatalities 5,411 538 6

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 7,429 785

Frontal fatalities 12,810 1059 22 17

Fatality reduction for driver air bags in all types of crashes: 14 10

127
TABLE C-25 - CAR DRIVERS, INCLUDING ALL MAKE-MODELS:

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

DRIVER FATALITIES RELATIVE TO RIGHT FRONT PASSENGER FATALITIES

EXTENDED DATA SET: ALL 1985-95 CARS WITH DRIVER AIR BAGS AND 3-POINT BELTS

VS. ALL 1985-95 CARS WITH 3-POINT BELTS ONLY

Driver

Fatalities

Right Front

Fatalities

Risk

Ratio

Percent

Reduction

Cars with belts only

Cars w. driver air bags

IN PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

5,422 5,880 .922

444 682 .651

(statistically significant difference: x2 = 29.98)

29

IN PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Cars with belts only

Cars w. driver air bags

4,576 4,591 .997

535 559 .957

(not a statistically significant difference: x

2 = 0.40)

Cars with belts only

Cars w. driver air bags

IN ALL CRASHES

16,423 17,622 .932

1,813 2,168 .836

(statistically significant difference: %2 = 10.39)

10

128
TABLE C-26 - DRIVERS WITH UNKNOWN BELT USE, BY IMPACT LOCATION.

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS

WITH UNKNOWN BELT USE ACCORDING TO FARS

LIMITED DATA SET: MAKE-MODELS THAT HAD MANUAL OR AUTOMATIC 3-POINT BELTS

AND ADDED DRIVER AIR BAGS WITHOUT CHANGING THE BELT SYSTEM,

EXCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 192 102

Purely frontal fatalities 166 99 -9

(not a statistically significant difference: x

2 = 0.23)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 192 102

Partially frontal fatalities 135 85 -19

(not a statistically significant difference: x

2 = 0.85)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 192 102

Frontal fatalities 301 181 -13

(not a statistically significant difference: %2 = 0.64)

Fatality reduction for driver air bags in all types of crashes: negative 8 percent

129
TABLE C-27 - DRIVERS WITH UNKNOWN BELT USE, BY IMPACT LOCATION

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS

WITH UNKNOWN BELT USE ACCORDING TO FARS

EXTENDED DATA SET: ALL 1985-95 CARS WITH DRIVER AIR BAGS AND 3-POINT BELTS

VS. ALL 1985-95 CARS WITH 3-POINT BELTS ONLY,

INCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Frontal Fat. Red.

for Air Bags (%)

Cars with Cars with

Belts Only Driver Air Bags Observed Adjusted

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 1921 201

Purely frontal fatalities 1996 194 7

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 1921 201

Partially frontal fatalities 1491 164 -5 -6

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 1921 201

Frontal fatalities 3487 358 2 -3

Fatality reduction for driver air bags in all types of crashes: 1 - 3

130
TABLE C-28 - DRIVERS WITH OVER 68 PERCENT EXPECTED BELT USE

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS WITH OVER 68 PERCENT EXPECTED BELT USE,

BASED ON THEIR STATE, ALCOHOL STATUS, VEHICLE AGE AND THE CALENDAR YEAR

LIMITED DATA SET: MAKE-MODELS THAT HAD MANUAL OR AUTOMATIC 3-POINT BELTS

AND ADDED DRIVER AIR BAGS WITHOUT CHANGING THE BELT SYSTEM,

EXCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 233 245

Purely frontal fatalities 266 193 31

(statistically significant difference: x

2

 ~ 7.97)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 233 245

Partially frontal fatalities 156 198 -21

(not a statistically significant difference: x

2

 = 1.79)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 233 245

Frontal fatalities 422 391 12

(not a statistically significant difference: x

2

 = 1-20)

Fatality reduction for driver air bags in all types of crashes: 8 percent

131
TABLE C-29 - DRIVERS WITH OVER 68 PERCENT EXPECTED BELT USE

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS WITH OVER 68 PERCENT EXPECTED BELT USE,

BASED ON THEIR STATE, ALCOHOL STATUS, VEHICLE AGE AND THE CALENDAR YEAR

EXTENDED DATA SET: ALL 1985-95 CARS WITH DRIVER AIR BAGS AND 3-POINT BELTS

VS. ALL 1985-95 CARS WITH 3-POINT BELTS ONLY,

INCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Frontal Fat. Red.

for Air Bags (%)

Cars with Cars with

Belts Only Driver Air Bags Observed Adjusted

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 1676 527

Purely frontal fatalities 1824 427 26 20

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 1676 527

Partially frontal fatalities 1168 396 -8 -9

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 1676 527

Frontal fatalities 2992 823 13

Fatality reduction for driver air bags in all types of crashes: 8

132
TABLE C-30 - DRIVERS WITH 57-68 PERCENT EXPECTED BELT USE

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS WITH 57-68 PERCENT EXPECTED BELT USE,

BASED ON THEIR STATE, ALCOHOL STATUS, VEHICLE AGE AND THE CALENDAR YEAR

LIMITED DATA SET: MAKE-MODELS THAT HAD MANUAL OR AUTOMATIC 3-POINT BELTS

AND ADDED DRIVER AIR BAGS WITHOUT CHANGING THE BELT SYSTEM,

EXCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 467 373

Purely frontal fatalities 425 283 17

(not a statistically significant difference: %2 = 3.09)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 467 373

Partially frontal fatalities 330 270 -2

(not a statistically significant difference: x

2 = 005)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 467 373

Frontal fatalities 755 553 8

(not a statistically significant difference: %2 = 0.94)

Fatality reduction for driver air bags in all types of crashes: 5 percent

133
TABLE C-31 - DRIVERS WITH 57-68 PERCENT EXPECTED BELT USE

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS WITH 57-68 PERCENT EXPECTED BELT USE,

BASED ON THEIR STATE, ALCOHOL STATUS, VEHICLE AGE AND THE CALENDAR YEAR

EXTENDED DATA SET: ALL 1985-95 CARS WITH DRIVER AIR BAGS AND 3-POINT BELTS

VS. ALL 1985-95 CARS WITH 3-POINT BELTS ONLY,

INCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Frontal Fat. Red.

for Air Bags (%)

Cars with Cars with

Belts Only Driver Air Bags Observed Adjusted

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 3479 762

Purely frontal fatalities 3399 543 27 21

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 3479 762

Partially frontal fatalities 2421 547 -3 -4

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 3479 762

Frontal fatalities 5820 1090 14

Fatality reduction for driver air bags in all types of crashes: 9

134
TABLE C-32 - DRIVERS WITH 40-57 PERCENT EXPECTED BELT USE

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS WITH 40-57 PERCENT EXPECTED BELT USE,

BASED ON THEIR STATE, ALCOHOL STATUS, VEHICLE AGE AND THE CALENDAR YEAR

LIMITED DATA SET: MAKE-MODELS THAT HAD MANUAL OR AUTOMATIC 3-POINT BELTS

AND ADDED DRIVER AIR BAGS WITHOUT CHANGING THE BELT SYSTEM,

EXCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 516 305

Purely frontal fatalities 572 202 40

(statistically significant difference: %2~ 22.44)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 516 305

Partially frontal fatalities 439 213 18

(not a statistically significant difference: x

2 = 3.20)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 516 305

Frontal fatalities 1011 415 31

(statistically significant difference: %2 = 15.50)

Fatality reduction for driver air bags in all types of crashes: 20 percent

135
TABLE C-33 - DRIVERS WITH 40-57 PERCENT EXPECTED BELT USE

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS WITH 40-57 PERCENT EXPECTED BELT USE,

BASED ON THEIR STATE, ALCOHOL STATUS, VEHICLE AGE AND THE CALENDAR YEAR

EXTENDED DATA SET: ALL 1985-95 CARS WITH DRIVER AIR BAGS AND 3-POINT BELTS

VS. ALL 1985-95 CARS WITH 3-POINT BELTS ONLY,

INCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Frontal Fat. Red.

for Air Bags (%)

Cars with Cars with

Belts Only Driver Air Bags Observed Adjusted

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 5127 548

Purely frontal fatalities 5649 369 39 33

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 5127 548

Partially frontal fatalities 3943 383 9

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 5127 548

Frontal fatalities 9592 752 27 22

Fatality reduction for driver air bags in all types of crashes: 17 13

136
TABLE C-34 - DRIVERS WITH 0-40 PERCENT EXPECTED BELT USE

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS WITH 0-40 PERCENT EXPECTED BELT USE,

BASED ON THEIR STATE, ALCOHOL STATUS, VEHICLE AGE AND THE CALENDAR YEAR

LIMITED DATA SET: MAKE-MODELS THAT HAD MANUAL OR AUTOMATIC 3-POINT BELTS

AND ADDED DRIVER AIR BAGS WITHOUT CHANGING THE BELT SYSTEM,

EXCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Cars with Cars with Frontal Fat. Red.

Belts Only Driver Air Bags for Air Bags (%)

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 466 193

Purely frontal fatalities 493 165 19

(not a statistically significant difference: %2~ 2.95)

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 466 193

Partially frontal fatalities 442 160 13

(not a statistically significant difference: x2 = 1.15)

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 466 192

Frontal fatalities 935 325 16

(not a statistically significant difference: x

2

 = 2.68)

Fatality reduction for driver air bags in all types of crashes: 11 percent

137
TABLE C-35 - DRIVERS WITH 0-40 PERCENT EXPECTED BELT USE

EFFECTIVENESS OF DRIVER AIR BAGS BASED ON REDUCTION OF

FRONTAL FATALITIES RELATIVE TO NONFRONTAL FATALITIES

ANALYSIS OF FATALLY INJURED DRIVERS WITH 0-40 PERCENT EXPECTED BELT USE,

BASED ON THEIR STATE, ALCOHOL STATUS, VEHICLE AGE AND THE CALENDAR YEAR

EXTENDED DATA SET: ALL 1985-95 CARS WITH DRIVER AIR BAGS AND 3-POINT BELTS

VS. ALL 1985-95 CARS WITH 3-POINT BELTS ONLY,

INCLUDING MAKE-MODELS THAT GOT ABS AT THE SAME TIME AS AIR BAGS

Frontal Fat. Red.

for Air Bags (%)

Cars with Cars with

Belts Only Driver Air Bags Observed Adjusted

PURELY FRONTAL CRASHES

(12:00 principal impact; most harmful event is not a rollover)

Nonfrontal fatalities 4091 326

Purely frontal fatalities 5000 261 34 28

PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact, excluding purely frontal crashes)

Nonfrontal fatalities 4091 326

Partially frontal fatalities 4078 272 16 15

ALL FRONTAL OR PARTIALLY FRONTAL CRASHES

(10:00-2:00 principal and/or initial impact)

Nonfrontal fatalities 4091 326

Frontal fatalities 9078 533 26 21

Fatality reduction for driver air bags in all types of crashes: 18 14

138
APPENDIX D

BELT USE OBSERVED IN STATE SURVEYS, 1990-94

(Source: NHTSA, Office of Occupant Protection)

Observed On-The-Road Belt Use

by Drivers and Right-Front Passengers (%)

State 1990 1991 1992 1993 1994

Alabama

Alaska

Arizona

Arkansas

California

Colorado

Connecticut

Delaware

DC.

Florida

Georgia

Hawaii

Idaho

Illinois

Indiana

Iowa

Kansas

Kentucky

Louisiana

Maine

Maryland

Massachusetts

Michigan

Minnesota

Mississippi

Missouri

42

45

55

34

67

50

59

45

49

53

41

85

35

48

47

61

58

32

39

35

68

28

51

47

22

54

53

66

65

52

71

51

61

42

49

60

54

85

45

51

52

68

64

48

37

35

72

35

64

52

32

54

58

66

73

55

70

50

71

70

59

57

51

83

53

65

56

71

70

41

47

36

75

31

54

53

24

70

55

69

73

55

83

53

71

68

62

62

57

84

59

67

56

73

70

40

48

36

72

34

64

55

25

70

55

69

60

51

83

54

72

63

62

61

57

84

61

68

56

73

70

58

50

36

69

47

66

57

43

68

1992

Population

4,140,000

590,000

3,830,000

2,400,000

30,870,000

3,470,000

3,280,000

690,000

590,000

13,490,000

. 6,750,000

1,160,000

1,070,000

11,630,000

5,660,000

2,810,000

2,520,000

3,760,000

4,290,000

1,240,000

4,910,000

6,000,000

9,440,000

4,480,000

2,610,000

5,190,000

139
Observed On-The-Road Belt Use

by Drivers and Right-Front Passengers (%)

State

Montana

Nebraska

Nevada

New Hampshire

New Jersey

New Mexico

New York

North Carolina

North Dakota

Ohio

Oklahoma

Oregon

Pennsylvania

Rhode Island

South Carolina

South Dakota

Tennessee

Texas

Utah

Vermont

Virginia

Washington

West Virginia

Wisconsin

Wyoming

National

Average

(PopulationWeighted)

1990

64

33

38

52

50

59

66

60

28

41

37

50

56

29

49

26

43

68

39

39

54

55

43

52

26

53.09

1991

67

33

68

49

58

67

68

60

30

50

37

70

60

28

60

33

51

68

45

40

58

69

43

58

66

58.76

1992

71

33

63

50

68

66

69

70

30

58

44

72

63

32

53

42

58

69

50

47

72

73

34

59

66

61.43

1993

71

54

70

51

71

75

72

80

30

62

47

73

68

32

59

26

58

69

50

54

73

78

52

64

67

65.66

1994

69

63

71

54

64

79

73

81

32

62

45

77

72

58

64

40

60

71

53

68

72

81

58

64

70

66.96

1992

Population

820,000

1,610,000

1,330,000

1,110,000

7,790,000

1,580,000

18,120,000

6,840,000

640,000

11,020,000

3,210,000

2,980,000

12,010,000

1,010,000

3,600,000

710,000

5,020,000

17,660,000

1,810,000

570,000

6,380,000

5,140,000

1,810,000

5,010,000

470,000

140