1999 SURVEY OF FRONT SEAT OCCUPANT RESTRAINT USE IN EIGHTEEN TEXAS CITIES

December 1999

This report was prepared in cooperation with the

Traffic Operations Division Texas Department of Transportation

Jeanne Swanson, Project Manager

National Highway Traffic Safety Administration U.S. Department of Transportation

DISCLAIMER

"The conclusions and opinions expressed in this document are those of the author, and do not necessarily represent those of the State of Texas, the Texas Department of Transportation or any political subdivision of the State or Federal Government."

ii

TABLE OF CONTENTS

PAGE

BACKGROUND..................................................................................................... 1

STUDY METHOD.................................................................................................. 2

RESULTS OF THE 1999 SURVEy....................................................................... 4

LONGITUDINAL LOOK...................................................................................... 11

CONCLUSIONS..................................................................................................... 19

SUMMARy............................................................................................................ 22

REFERENCES........................................................................................................ 23

iii

LIST OF TABLES

PAGE

TABLE 1 1999 OCCUPANT RESTRAINT USE BY GENDER................................... 4

TABLE 2 1999 DRIVER RESTRAINT USE BY AGE.................................................. 5

TABLE 3 1999 PASSENGER RESTRAINT USE BY AGE.......................................... 5

TABLE 4 1999 PERCENTAGE OF RESTRAINED DRIVERS BY AGE AND GENDER............................................................................... 6

TABLE 5 1999 PERCENTAGE OF RESTRAINED PASSENGERS BY AGE AND GENDER............................................................................... 6

TABLE 6 1999 OCCUPANT RESTRAINT USE BY VEHICLE TypE........................................................................................ 7

TABLE 7 ASSOCIATION BETWEEN DRIVER AND PASSENGER RESTRAINT USE........................................................................................... 8

TABLE 8 1999 PERCENTAGE OCCUPANT RESTRAINT USE IN THE 18 STUDY CITIES............................................................................ 9

TABLE 9 1999 PERCENTAGE DRIVER AND PASSENGER RESTRAINT USE IN THE 18 STUDY CITIES............................................ 10

TABLE 10 PERCENT OF DRIVERS RESTRAINED BY CITY OVER TIME.................................................................................................... 13

TABLE 11 PERCENT OF PASSENGERS RESTRAINED BY CITY OVER TIME.................................................................................................... 14

TABLE 12 DRIVER AND PASSENGER RESTRAINT USE BY GENDER AND YEAR................................................. ................................................... 16

TABLE 13 DRIVER RESTRAINT USE OVER TIME BY AGE AND GENDER................................................................................ 19

iv

LIST OF FIGURES

PAGE

FIGURE 1 STUDY CITIES IN THE TEXAS SAFETY BELT OBSERVATIONAL SURVEY........................................................ 3

FIGURE 2 FRONT SEAT OCCUPANT RESTRAINT USE BY yEAR.......... 12

FIGURE 3 DRIVER RESTRAINT USE BY AGE AND YEAR.................... 17

v

1999 SURVEY OF FRONT SEAT OCCUPANT RESTRAINT USE IN EIGHTEEN TEXAS CITIES

Background

A mandatory belt use law (MUL) was passed in the 1985 general session of the Texas

Legislature and went into effect without sanctions September 1, 1985; enforcement with the

imposition offmes began on December 1, 1985. This law requires drivers and front seat passengers

to use safety belts. Drivers are responsible for passengers under 15 years of age, and may be issued

a citation for a front seat minor passenger's failure to use a safety belt. The Texas MUL was

amended in 1999 to include passengers under 15 years of age occupying any seat in the vehicle

equipped with a safety belt. These requirements apply to passenger cars and light pick-up trucks of

not more than 3/4-ton carrying capacity. It exempts persons for medical reasons (requiring a written

statement from a licensed physician), postal employees in box-to-box delivery of mail, and

employees of public or private utility companies who are engaged in meter reading or similar duty

requiring frequent entry and exit from a vehicle. Use or non-use of safety belts is not admissible

evidence in a civil trial. The fine for non-compliance is $25 - $50. The Texas MUL allows for

primary enforcement.

In 1984, the Texas Transportation Institute (TTl) began collecting occupant restraint use data

in a sample of Texas cities for the Texas Department of Transportation (TxDOT). At that time

occupant restraint legislation was not under consideration in Texas. It was agreed, however, that

collecting baseline data on occupant restraint use would prove beneficial for information purposes

in response to legislative initiative. The background, methodology and results of the baseline study,

as well as a review of other relevant studies, were presented in a 1985 report (Hatfield, et aI.,

1985).

In order to assess changes in occupant restraint use after passage of the law and to provide

current usage rates, TTl has continued to conduct observational surveys each year since the MUL

has been in effect. From 1987 through 1990, data was collected at two intervals annually (January

1

and June). From 1991 through 1999, the survey was conducted at one interval during late

spring/early summer. The 1999 survey was conducted May 17 through June 17. This report

presents the results of the 1999 survey, and compares these findings with the results of previous

surveys.

Study Method

For the 1985 pre-law observational survey 12 Texas cities were selected to represent the

major population centers in the East, Central, and Gulf Coast regions of the State, as well as the less

populated areas of West Texas, the Panhandle, and the Rio Grande Valley. At the request of

TxDOT, two additional cities were included in the 1986 post-law survey and four additional cities

were included in the 1988 post-law survey. Figure 1 shows the sample of 18 cities currently used

as observation sites.

In each study city, six sites were selected to represent a geographic cross-section of the city.

Each intersection selected for observation was controlled by either a stop sign or traffic signal, and

on roadways with sufficient traffic volume such that 150 vehicles could be observed within an hour

or less time. All observations were recorded during daylight hours and on weekdays.

Observations were limited to drivers and right front seat (outboard) passengers, with restraint

use determined by the use of a shoulder harness. Eligible vehicles included passenger cars and

pick-up trucks.

The following information was collected for each eligible vehicle:

• Driver and front seat outboard passenger restraint use (yes or no)

• Front seat occupant gender (male or female)

• Estimated driver age (15-19, 20-60, 61+)

• Estimated front outboard passenger age (0-4, 5-14, 15-19,20-60,61+)*

• Pick-up truck (yes or no)

* No information on passengers under 15 was recorded in the 1985 baseline study.

2

FIGURE 1 STUDY CITIFS IN THE SAFETY BELT OBSERVATIONAL SURVEY

• Lubbock

AbUcnc •

• Midland

Ft. Worth· • Dallas .Tylcr

• Waco

Bryan/Collcge Station. Beaumont

Austin· •

3

The observations were conducted by Texas A&M University students and TTl project staff.

Each observer was provided individual instruction and field training by TTl project staff. To

assure accuracy of data collection, observers were monitored during the survey period by the study

staff.

Results of the 1999 Survey

In the combined 18-city sample, data regarding 20,691 front seat occupants were

collected at a total of 108 intersections. The percentage of front seat occupants restrained in

these urban area locations was 78.0. 79.5 percent of the drivers and 72.6 percent of the

passengers observed were using safety belts.

Analysis of the sites in each city where detailed data were collected revealed a higher usage

rate for females than males. As shown in Table 1, female drivers and passengers were restrained

over 7 percentage points more often than male drivers and passengers (83.9 percent compared to

76.4 percent for drivers and 76.0 percent compared to 68.3 percent for passengers).

TABLE 1. 1999 OCCUPANT RESTRAINT USE BY GENDER

Driver Passenger

Male Female Male Female

% Restrained 76.4 83.9 68.3 76.0

% Unrestrained 23.6 16.1 31.7 24.0

Total Occupants (N) 9,558 6,812 1,918 2,403

4

The driver restraint usage rate increased as age increased. The restraint usage rate for drivers

over age 60 was 83.0 percent compared to 75.7 percent for teenage drivers (Table 2). For

passengers, the relationship between age and restraint use was similar. Generally, restraint use

increased as age increased (Table 3). The age group with the lowest passenger restraint use was

children in the 5 to 14 year age group (62.5 percent). Infants and younger children (0 to 4 years)

were restrained 65.9 percent of the time. It should be noted that a shoulder belt placed behind a

child's back is counted as non-use, and this practice is commonly observed among children,

therefore contributing to the lower usage rate.

TABLE 2. 1999 DRIVER RESTRAINT USE BY AGE

Driver Age

15 -19 20-60 Over 60

0/0 Restrained 75.7 79.3 83.0

% Unrestrained 24.3 20.7 17.0

Total Drivers (N) 366 14,797 1,207

TABLE 3. 1999 PASSENGER RESTRAINT USE BY AGE

Pnssenger Age ,

0-4· 5 -14 15-19 20 -60 Over 60

% Restrained 65.9 62.5 71.6 73.2 81.7

0/0 Unrestrained 34.1 37.5 28.4 26.8 18.3

Total Passengers (N) 44 466 486 2,926 399

*Restraint use was consIdered eIther safety belt or child safety seat.

5

Cross-classification of the data by age and gender (Table 4) revealed that female drivers are

more likely than male drivers are to wear safety belts at every age level. The difference in usage

rates by males and females was smallest in the oldest age category and was largest among teenage

drivers.

TABLE 4. 1999 PERCENTAGE OF RESTRAINED DRIVERS BY AGE AND GENDER

Drivelr Gender

Driver Age Male Female

15 - 19 (n=366) 72.0 81.1

20 - 60 (n=14,797) 76.1 83.7

Over 60 (n=1,207) 80.7 86.6

Restraint use among passengers was also analyzed by gender and age (Table 5). The highest

restraint use was evidenced by females over 60 (84.7 percent). Males 5 to 14 years evidenced the

lowest level of use (61.7 percent).

TABLE 5. 1999 PERCENTAGE OF RESTRAINED PASSENGERS BY AGE AND GENDER

Passenger Gender

Passenger Age Male Female

0-4 (n=44) 68.4 64.0

5 - 14 (n=466) 61.7 77.0

15 - 19 (n=486) 72.1 71.0

20 - 60 (n=2,926) 68.3 77.0

Over 60 (n=399) 74.6 84.7

6

For both drivers and passengers, restraint use was found to be higher for occupants of

passenger cars than for pick-up trucks, as seen in Table 6. The difference was 7 percentage points

for drivers and 8.4 percentage points for passengers.

TABLE 6. 1999 OCCUPANT RESTRAINT USE BY VEHICLE TYPE

Driver Passenger

Car Pick-up Car Pick""up

0/0 Restrained 81.2 74.2 74.3 65.9

0/0 Unrestrained 18.8 25.8 25.7 34.1

Total Occupants (N) 12,388 3,982 3,410 911

As was true in previous surveys, there was a strong association between driver restraint use

and passenger restraint use, often referred to as the audience effect. In the 1999 survey, 26 percent

of all vehicles observed had a passenger in the front outboard seating position. In this sample of

4,320 vehicles, if the driver was restrained, it was very likely that the passenger was also restrained

(83.3 percent of the time). Likewise, if the driver was unrestrained, it was very likely that the

passenger was also unrestrained (68.7 percent of the time). Restrained passengers were riding with

unrestrained drivers only 31.3 percent of the time (Table 7).

7

TABLE 7. ASSOCIATION BETWEEN DRIVER AND PASSENGER RESTRAINT USE

Drivers Restrained Pa.ssengers Restraim:d

% Unrestrained % Restrained Total

% Unrestrained 68.7 (614) 31.3 (280) 100 (894)

% Restrained 16.7 (572) 83.3 (2854) 100 (3426)

Table 8 shows the observed restraint usage rate for each of the 18 cities using data from the

6 sites used to represent geographic cross sections of each city. These estimates provide the usage

rate for all front seat occupants observed in each city and does not differentiate among drivers and

passengers. Citywide occupant restraint use ranged from a low of70.1 percent in Laredo to a high

of 89.1 percent in Amarillo. Seven of the 18 cities had usage rates above 80 percent for drivers and

passengers in passenger cars and pick-ups combined.

The data that provided information regarding driver and passenger were analyzed separately

for each of the 18 cities. Table 9 shows that driver restraint use ranged from a low of 72.2 percent

in Laredo to a high of 89.8 percent in Amarillo. Passenger restraint use ranged from 62.7 percent

in Beaumont to 86.2 percent in Amarillo. The total percentage of drivers restrained was greater than

the observed percentage of passengers restrained, with an average difference of approximately 7

percentage points.

8

TABLE 8. 1999 PERCENTAGE OCCUPANT RESTRAINT USE IN THE 18 STUDY CITIES

Number Percent CITY Observed Restrained

Abilene 1,128 72.8

Amarillo 1,086 89.1

Austin 1,112 84.8

Beaumont 1,129 75.0

Brownsville 1,203 72.3

Bryan/College Station 1,101 85.9

Corpus Christi 1,124 76.7

Dallas 1,192 72.9

EI Paso 1,165 84.0

Ft. Worth 1,157 72.2

Houston 1,191 76.0

Laredo 1,211 70.1

Lubbock 1,126 75.6

Midland 1,096 82.3

San Antonio 1,165 77.5

Tyler 1,163 80.7

Waco 1,112 83.7

Wichita Falls 1,228 75.4

9

TABLE 9. 1999 PERCENTAGE DRIVER AND PASSENGER RESTRAINT USE IN THE 18 STUDY CITIES

CITY Drivers Passengers

Abilene 74.9 63.9

Amarillo 89.8 86.2

Austin 86.9 75.0

Beaumont 78.0 62.7

Brownsville 73.8 67.3

Bryan/College Station 86.4 83.2

Corpus Christi 78.9 67.8

Dallas 72.5 74.2

El Paso 85.4 79.2

Ft. Worth 73.4 68.1

Houston 76.8 73.1

Laredo 72.2 63.5

Lubbock 77.3 68.7

Midland 84.3 72.7

San Antonio 80.0 69.1

Tyler 81.5 77.7

Waco 84.2 81.7

Wichita Falls 74.9 76.8

10

Longitudinal Look

Conducting annual surveys of restraint use is useful for analyzing changes over time. It is

important when using longitudinal data to assure that the data are comparable over time. If the

variable being measured is not a fixed population, as in the traffic observed to collect restraint usage

data, comparability can be achieved by: 1) holding the sites and data collection procedures constant

within cities, or 2) by using identical sampling methods each year within cities. Neither of these

safeguards has been kept throughout the survey period from the beginning (1985) to the current wave

of data collection. The sites and data collection procedures were held constant from 1985 through

1991. However, the implementation of a statewide sampling methodology in 1992 introduced a

change in both the site selection and the data collection procedures used for the 18-city surveys. In

an effort to consolidate survey efforts, data representing citywide estimates were collected from sites

selected in the probability based sample design to estimate statewide restraint use. The data

collection procedure was also changed from a quota of observations per site to a time based volume

of observations per site. The result was that the 1992-1998 data for each city was not comparable

to the cross-sectional data of 1985-1991. Nevertheless, the 1992-1998 data was collected in such

manner as to describe a city-wide estimate of front seat restraint use, and was therefore reported and

analyzed in comparison with prior years' city-wide results. The 1999 survey of front seat occupant

restraint use in 18 Texas cities represents a transition back to a methodology that is more consistent

with the pre-1992 surveys. In the 1999 survey, a quota of observations were made at half the

number of sites (6) using similar methods as were used in each city in the 1985-1991 surveys. This

provides a snapshot look at restraint use in the 18 cities for 1999 that represents a cross-section of

each city, but is not statistically comparable (at the city level) to results from previous years.

Therefore, in this year's report the longitudinal look is restricted to the presentation of results by

year, and the trend analysis at the city level is omitted.

Figure 2 is a composite view of restraint use for each year using the various data collection

methods described above. The data used for this graph are from the combined sites across all cities,

and include driver and outboard passenger belt use. Tables 10 and 11 show driver and passenger

restraint use for each year in each city. Again, variations over time may be attributable in part by

variations in the study methodology.

11

100.0

90.0

80.0

70.0

60.0 I-' N

50.0

40.0

30.0

20.0

10.0

0.0

%

1985 1986 1/87 6/87 1/88 6/88

Figure 2.

1/89 6/89 1/90 6/90 1991 1992 1993 1994 1995 1996 1997 1998 1999

Front Seat Occupant Restraint Use By Year

TABLE 10. PERCENT OF DRIVERS RESTRAINED BY CITY OVER TIME

City 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999

Abilene NA NA NA 52.8 57.3 63.7 69.3 75.6 73.8 71.9 75.5 78.4 77.1 74.5 74.9

Amarillo 10.8 65.2 66.2 60.4 57.8 61.4 61.7 71.2 72.4 75.9 70.0 70.4 82.9 87.5 89.8

Austin 28.1 74.6 74.3 72.7 70.1 76.8 79.1 81.2 81.2 85.0 88.7 86.1 87.5 90.7 86.9

Beaumont NA 60.0 52.0 59.3 65.2 72.0 73.5 66.8 75.4 71.0 63.7 64.8 70.9 75.5 78.0

Brownsville 3.4 63.3 43.6 35.9 51.5 63.5 68.9 NA 67.7 79.3 80.1 81.3 77.8 77.2 73.8

Bryan/CS 16.4 70.4 64.1 61.5 56.9 63.7 67.8 87.2 83.9 87.7 88.3 86.8 87.4 87.5 86.4

Corpus Christi 13.4 76.8 65.9 83.3 75.6 77.5 71.4 81.0 76.8 83.3 81.8 80.7 82.7 84.1 78.9

Dallas 20.6 70.9 58.4 67.6 59.2 67.1 66.0 77.0 55.2 72.2 76.4 80.6 73.9 73.8 72.5

El Paso 15.0 63.8 63.9 72.0 64.6 72.9 68.2 62.6 68.9 65.4 74.0 68.0 74.4 83.5 85.4

Ft. Worth NA 63.3 61.2 55.0 57.8 60.7 62.1 62.2 68.6 70.0 67.4 80.5 75.8 80.1 73.4

Houston 19.7 68.6 66.0 53.3 62.1 65.4 58.3 76.5 70.3 76.1 73.9 79.2 81.3 75.3 76.8

Laredo NA NA NA 50.1 61.8 73.0 78.4 71.0 72.8 71.9 78.0 76.7 79.0 73.1 72.2

Lubbock 14.3 63.3 57.6 61.0 66.4 72.0 60.5 82.4 78.8 85.7 77.8 76.0 76.2 78.3 77.3

Midland NA NA NA 55.2 69.7 67.9 73.3 86.6 85.8 86.7 86.5 84.2 80.3 83.5 84.3

San Antonio 13.3 60.6 58.7 47.4 44.2 50.2 56.3 78.6 68.8 72.4 71.8 76.1 75.1 76.8 80.0

Tyler 16.7 67.0 59.2 72.4 76.5 80.8 81.1 77.6 76.6 76.9 83.9 77.4 83.9 83.9 81.5

Waco 9.7 57.5 48.0 45.9 47.9 53.8 55.8 73.3 74.4 73.0 79.9 75.3 78.0 78.0 84.2

Wichita Falls NA NA NA 59.9 56.3 73.6 64.2 71.6 72.8 74.8 75.9 76.3 71.0 76.9 74.9

Average 15.2 66.8 60.5 59.2 61.2 67.6 67.5 77.3 74.5 77.2 78.7 78.0 79.4 80.8 79.5

TABLE 11. PERCENT OF PASSENGERS RESTRAINED BY CITY OVER TIME

City 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 Abilene NA NA NA 39.2 52.6 61.6 67.2 69.0 62.1 63.9 73.2 74.6 68.6 68.2 63.9

Amarillo 8.7 55.8 52.4 46.8 41.8 51.2 53.3 67.0 67.0 68.0 60.1 67.2 77.1 81.8 86.2

Austin 18.1 60.5 64.4 67.3 60.3 65.4 73.4 69.7 76.8 77.7 84.2 90.8 83.5 82.1 75.0

Beaumont NA 47.2 45.5 50.9 54.3 62.0 66.0 61.5 67.4 74.2 49.3 60.9 62.9 66.3 62.7

Brownsville 2.9 54.6 32.5 24.1 35.1 43.3 50.1 NA 56.2 63.3 69.6 70.0 58.8 59.1 67.3

Bryan/CS 14.7 60.4 58.1 58.3 56.5 53.8 58.3 78.0 76.5 75.8 79.8 84.7 79.5 79.2 83.2

Corpus Christi 8.2 67.0 59.3 75.2 67.4 67.3 62.1 71.7 62.7 70.0 69.6 70.1 77.0 80.4 67.8

Dallas 11.9 68.3 47.2 54.0 55.7 55.3 58.1 54.8 49.2 68.7 66.0 63.4 65.7 75.8 74.2

EI Paso 11.4 60.3 60.7 58.8 49.6 60.1 54.6 53.2 56.4 56.7 68.2 55.6 59.5 74.5 79.2

Ft. Worth NA 54.0 53.2 45.9 48.1 50.2 46.4 34.8 56.8 75.8 61.8 89.4 77.0 78.9 68.1

Houston 8.2 6.6 59.6 52.6 52.9 49.7 42.9 76.1 62.9 66.7 69.8 68.2 84.1 73.3 73.1

Laredo NA NA NA 42.7 52.9 55.8 67.4 59.0 61.3 55.2 63.7 62.4 66.7 60.5 63.5

Lubbock 9.3 53.0 50.8 40.9 44.1 57.5 51.7 72.8 71.8 72.1 69.9 73.4 69.9 76.6 68.7

Midland NA NA NA 40.2 56.5 65.1 56.9 80.6 67.4 79.3 78.2 68.5 72.5 76.2 72.7

San Antonio 4.9 46.6 44.4 32.2 35.6 34.2 41.6 67.7 59.2 71.4 59.8 69.1 66.2 70.2 69.1

Tyler 12.1 56.9 48.8 64.3 72.8 69.7 76.4 65.8 62.9 68.7 79.8 71.4 78.0 71.3 77.7

Waco 6.7 49.2 35.3 32.3 36.4 47.1 41.1 65.3 82.1 73.3 76.8 84.5 71.8 75.3 81.7

Wichita Falls NA NA NA 46.2 48.1 67.0 56.5 53.5 61.5 59.7 54.8 70.7 58.6 67.2 76.8

Average 9.6 58.7 51.1 48.2 50.7 55.0 56.1 67.4 64.2 68.3 69.7 71.0 71.1 73.4 72.6

Table 12 shows changes over time in driver and passenger restraint use by males and females

for all cities included in the observational survey. These data show a drop in use by both males and

females following the first full year of the MUL. However, the drop in female restraint use was not

as large and rebounded more quickly than usage for males. Belt use among males and females in

1992 was approximately 10 percentage points higher than 1991. Again, the sites included in the

1992 survey were a subset of earlier surveys and therefore do not represent a replication of earlier

surveys. A significant decrease from the 1992 usage rate was observed in 1993 for males and

females. In 1994, however, the male and female driver restraint usage rate returned to approximate

the 1992 rate. A small, but statistically significant increase in belt use for male drivers was observed

in 1995. This increase for males was again observed in the 1997 survey and continued to be

observed in the 1998 survey. The usage rate for male drivers remained statistically the same in 1999,

while the female driver restraint use slipped to the 1996 level.

Table 12 also shows a similar trend in restraint use for male and female passengers over time.

As with drivers, male passengers were less likely to be belted prior to safety belt legislation (7.5

percent male passengers restrained and 10.8 percent female passengers restrained in 1985). Male

passenger usage dropped to a greater degree after the first year of the enactment period (from 55.1

percent in 1986 to 44.7 percent in 1987, compared to 58.0 and 53.4 percent for female passengers).

The decrease in passenger restraint use from June of 1987 to June of 1988 was significantly smaller

for both males and females. The slow downward trend was reversed for both male and female

passengers in 1989. The trend of gradual increases in passenger restraint use for both males and

females has continued in the 90's. However, in 1999 the passenger restraint usage rate for females

dipped slightly. This decrease was not statistically significant.

15

TABLE 12. DRIVER AND PASSENGER RESTRAINT USE BY GENDER AND YEAR

Percent Rlestrained Percent Restrained

Year Drivers PaSSe][lgers

Male Female Male Female

1985 13.8 16.9 7.5 10.8

1986 64.8 67.8 55.1 58.0

1987 (June) 57.0 63.8 44.7 53.4

1988 (June) 54.9 64.7 42.2 50.0

1989 (June) 57.2 66.3 45.4 54.8

1990 (June) 64.2 71.8 52.1 57.1

1991 63.9 72.3 51.6 59.1

1992 73.5 82.7 60.0 72.6

1993 70.1 80.7 60.5 67.1

1994 73.2 83.0 62.4 72.6

1995 74.9 84.1 63.0 74.5

1996 73.8 83.8 67.1 73.7

1997 75.2 85.0 66.8 74.4

1998 76.8 86.2 67.4 77.6

1999 76.4 83.9 68.3 76.0

Changes in restraint use by the three age groups over time were also analyzed. The results

revealed that the oldest group of drivers (over 60 years) showed the highest increase in belt use for

the first year after the law went into effect (52 percentage points) and the lowest decrease in belt use

during the second year (four percentage points) compared to the other two age groups (Figure 3).

Although teen restraint use steadily decreased since 1986, a dramatic increase occurred in 1989 and

16

% 100

80

60

40

20

o 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99

-e- Teen + Adult -1$l- Senior

Figure 3. Driver Restraint Use By Age and Year

continued in 1990 and 1991 for teen belt use. Adult and senior use both increased significantly in

1990 (adults by 6.5 percentage points and seniors by 5.0 percentage points) and did not significantly

change in 1991. In 1992, all three age groups experienced significant increases. However, in 1993,

teen and older driver restraint use remained constant, while the adult age 20 to 60 group significantly

increased restraint use. Both teens and adults showed increases in restraint use in 1994, while no

change was observed in senior belt use. In 1995 a significant increase in adult belt use was

observed, while teenage and senior belt use stayed statistically the same. Adult belt use returned to

the 1994 level in 1996. The adult category significantly increased again in 1997 and 1998, and teen

belt use increased dramatically in 1998. However, in 1999 belt use among teens returned to the pre-

1998 level. The 4.4 percentage point difference from 1998 to 1999 in belt use among teens is not

a statistically significant change. Much larger sample sizes for this group are required to detect a

.05 level of significance. Belt use among seniors stayed statistically the same in 1999 as the prior

year. The 1.1 percentage point decrease among adult drivers (20-60 years) was statistically

significant.

When gender and age were analyzed together (Table 13), the results show that through the

years males and females at each age level have seldom shown the same belt wearing behavior. With

some exceptions in some years, females in each age group were restrained more often than males.

Of particular noteworthiness is the return to the 1997 level of belt use for teenage female drivers,

which significantly affected the decline in teen belt use overall. Also note that decreases observed

in 1999 in female restraint use among those 20 and above show a reversal of the preceding two-year

trend.

18

Year

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

Conclusions

TABLE 13. DRIVER RESTRAINT USE OVER TIME BY AGE AND GENDER

Percent Restrained By Age and Gender

15~19 20··60 Over 60

Male Female Male Female Male Female

6.5 12.0 13.8 16.9 15.9 18.3

46.9 51.9 64.9 68.0 68.8 69.3

45.1 44.0 56.9 63.7 61.8 69.3

38.9 46.8 54.8 59.7 63.0 72.6

51.0 61.9 57.0 66.3 63.6 69.5

54.9 63.4 64.3 71.9 67.7 74.2

53.1 60.7 64.0 72.4 67.0 74.6

65.5 73.9 73.3 82.6 77.4 85.5

64.5 71.0 69.7 80.7 75.7 84.0

72.6 79.4 72.7 83.0 78.3 84.4

70.4 69.2 74.8 84.3 76.8 84.5

72.0 81.4 73.4 83.6 79.5 87.9

68.7 79.0 75.0 85.0 79.5 85.9

72.2 91.2 76.4 85.8 81.9 88.8

72.0 81.1 76.1 83.7 80.7 86.6

The initial survey of 1985 showed front seat occupant restraint use in 12 Texas cities

averaging 14.2 percent for all front seat occupants observed. Not surprisingly, a dramatic increase

in belt use was observed during the first year of the post-MUL period. Restraint use rates in the

1986 survey were 64.9 percent overall. At that time, compliance was considerably higher than

reported usage rates in other MUL States.

19

In the second year of the post-law period (1987), observed usage rates for front seat

occupants decreased by approximately seven percent to a 57 percent usage rate for all cities

combined. During this second year of MUL experience, decreases in use were attributed to those

segments of the population that were least likely to be restrained prior to seat belt legislation.

Specifically, males, teens, and pick-up occupants showed the largest decreases in use.

The January survey of 1988 seemed to support further evidence of the post-law decline. The

average belt use rate of 52 percent for 18 cities surveyed in January of 1988 was six percentage

points lower than June of 1987. One factor contributing to the decrease was the inclusion of the four

additional cities for this survey wave. Without the new cities the 14-city average was 55.7 percent.

Observed usage rates rose to an average of 56.9 percent for the 18 cities surveyed in June of

1988. As with the downward shift from June of 1987 to June of 1988, this upward change may have

been due in part to normal fluctuations in the data.

The 1989 survey indicated a leveling off for the average restraint usage rate across the 18

study cities of 59 percent. Three survey waves (June 1988 through June 1989) reflected a

consistency in the overall restraint use average that, incidentally, was not reflected uniformly at the

city level.

The 1990 survey revealed a significant increase in safety belt use. The average percentage

of front seat occupants restrained across all 18 cities was the highest ever observed in the June

survey wave. Every city in the sample experienced an increase in driver restraint use from June of

1989 to June of 1990, with the exception of Midland (which experienced a statistically non­

significant decrease in use). Eight of the 18 cities reached the national (NHTSA) and state (TxDOT)

target goal of70 percent by 1990.

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No significant changes in the combined 18-city safety belt use rate were revealed in the 1991

survey from June of 1990. At the city level, six cities showed increases and five cities showed

decreases in belt use. Six of the 18 cities surveyed sustained a usage rate above 70 percent.

The 1992 survey revealed significant increases in front seat restraint use in 11 cities. Five

of these cities showed increases in driver restraint use by over 15 percentage points. Eight of the 18

cities surveyed in 1992 sustained a usage rate above 70 percent, and of those, three had over 80

percent restraint use by front seat occupants.

A statistically significant change in the combined 18-city safety belt use rate was not

observed in 1993 from the overall rate observed in 1992. At the city level, only one city increased

in driver usage in 1993, whereas four cities had statistically significant decreases. In 1993, 12 of the

18 cities had occupant restraint usage rates above 70 percent, and two cities had usage rates above

80 percent.

Statistically significant increases in the combined 18-city safety belt use rates were observed

in 1994, 1995, 1996, and 1997. The safety belt use rate for front seat occupants in 1998 was

statistically equal to the estimate in 1997. All of the 18 cities had safety belt use rates above 70

percent in 1998, and seven cities were above 80 percent. The national goal of 85 percent by 2000

was attained in three cities. In 1999, the usage rate in the 18 urban areas increased again with

statistical significance. Using six sites to observe 900 vehicles in each city revealed that the 80

percent restraint usage rate for front seat occupants was attained in seven cities, as in 1998. Amarillo

and Bryan/College Station also surpassed the 2000 goal of 85 percent.

Analysis of safety belt use for males and females and for the three age groups revealed

somewhat comparable patterns in the 1999 survey to previous observed usage patterns. Females

evidenced higher usage rates than males, both as drivers and as passengers. Teenage driver restraint

use was lowest, and senior driver restraint use was highest. An upward progression in belt use by

age was found for passengers. Infants and children were least likely to be restrained (65.9 and 62.5

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percent, respectively) and passengers over 60 were most likely to be restrained (81.7 percent).

Occupants of cars (driver and .passenger) were restrained 79.7 percent of the time. Whereas

occupants of pick-up trucks (driver and passenger) were restrained 72.6 percent of the time, a

difference of 7.1 percentage points.

As in earlier years, the audience effect was found to be quite strong. In other words, two

front seat occupants were shown to behave in a very similar manner in terms of restraint use--either

both individuals used the available restraint system, or both rode unrestrained. The gap between

driver restraint use and passenger restraint use was 6.9 percentage points, a difference that was

exactly the same as in 1998, and which is consistent with the trend observed in previous surveys.

SUMMARY

In summary, 1999 observation of occupant restraint use revealed an average usage rate across

the 18 cities of78.0 percent. All of the 18 cities in the sample had greater than 70 percent usage

rates for front seat occupants. Additionally, seven cities surveyed had greater than 80 percent

restraint usage for front seat occupants, which was established as a national target usage rate for

1994. A current national goal is for 85 percent restraint usage rate by the year 2000. This goal has

been reached in Amarillo and Bryan/College Station in 1999.

The collection of data specific to the occupants observed revealed that female drivers used

seat belts more often than male drivers, and female passengers were belted more often than male

passengers were belted. Children and infants were least likely to be buckled as passengers.

Additionally, restraint use in cars was higher than restraint use in pick-up trucks.

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REFERENCES

Hatfield, N.G., W.M. Hinshaw, N.G. Bunch, and R. Bremer, Observed Pre-Law Safety Belt Use by Adult Front Seat Occupants in Twelve Texas Cities, Texas Transportation Institute, Texas A&M University System, December, 1985.

Downie, N.M. and R.W. Heath, Basic Statistical Methods, Harper and Row, New York, NY, 1965.

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