2002 Seatbelt Final Report

THE

2002 SEAT BELT/MOTORCYCLE HELMET SURVEY

Prepared for: The Office of Highway Safety Division of Public Safety Planning Mississippi Department of Public Safety October 2002

Prepared by: David R. Parrish and James W. Landrum Social Science Research Center Mississippi State University Mississippi State, MS 39762

October 24, 2002

SSRC

Social Science Research Center Mississippi State University

HELPING OUR NATION SAVE LIVES Prelude The goal has been set. By 2003 the Bush Administration wants a nationwide 78 percent of automobile occupants to be restrained by seat belt devices. According to Jeffrey W. Runge, M.D., Administrator of the National Highway Traffic Safety Administration (NHTSA), in 2002 seat belt usage is continuing its upward trend to an impressive 75 percent national usage rate – its highest level since national surveys first started in 1994.

Usage is up 2 percent from 73 percent in 2001. This

increase translates into an estimated 6 million new users of safety restraints and 500 saved lives.1 Death shadows over every automobile accident. It waits for the opportunity to claim another human life. In 2000 an average of 115 people died every day in motor vehicle accidents. That is one life claimed every 13 minutes! During the same year there were more than 41,000 deaths and three million injuries as a result of crashes.

These vehicle crashes cost us, the American people,

approximately $150 billion in economic costs, and it is these costs that are passed on to every person in America in the range of about $580 per person per year.2 Despite the dollar amounts associated with traffic fatalities, it is more of a tragic and distressing fact that the leading cause of death is motor vehicle accidents for ALL Americans of every age from 4 to 33 years old.3 This fact should be the driving force for the continued monitoring of seat belt usage and the enforcement of seat belt laws. As the Mississippi Click It or Ticket television commercial best states, “We are GOING to save lives.”4 Contrary to the accident death rate in 2000, seat belts saved the lives of an estimated 11,889 people that year. 3 In test after test, statistic after statistic, the use of seat belts proves to be the most effective safety device in reducing the chances of death or serious bodily injury in 1

U.S. Department of Transportation Press Release, September 9, 2002 (http://www.nhtsa.dot.gov) Buckle Up America Faith Community Leader Safety Facts, 2002 (http://www.nhtsa.dot.gov) 3 NHTSA Occupant Protection Division – Winter 2002 (http://www.nhtsa.dot.gov) 2

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motor vehicle crashes. It takes only a few seconds to fasten a seat belt, and the importance of using this restraint device cannot be overstated. Figure 1 below exemplifies the benefits of using seat belts by graphically representing the cumulative estimated number of lives saved by safety belt use from 1975 to 2000. It is imperative that Mississippians understand the difference wearing a seat belt can make in crash occurrences, and it is the duty of Mississippi to provide the information that will instill a belief and encourage a behavior that saves lives. Without a primary seat belt law Mississippi law enforcement is limited, but Mississippi must undertake the commitment to ensure seat belt usage rates continue to rise and lives continue to be saved.

Figure 1: Cumulative Estimated Number of Lives Saved Nationwide by Safety Belt Use 1975 – 2000

125,000

4

1994

123, 213

112, 016

100, 998

48 90,2

1975- 1993 1992

79,8

44

38

70,0

Source: Traffic Safety Facts 2000: Occupant Protection U.S. Department of Transportation, National Highway Traffic Safety Administration DOT HS 809 327

52,4

25,000

60,8

91

50,000

34

75,000

135, 102

100,000

0 1995

1996

1997

1998

1999

Excerpt from television commercial for the 2001 MS Click It or Ticket Campaign. 2

2000

SEAT BELT/MOTORCYCLE HELMET SURVEY Introduction Two full Seat Belt/Motorcycle Helmet Surveys were conducted in the Spring of 2002. The first survey was conducted prior to the implementation of the Click It or Ticket Project, and the second survey was conducted after the implementation of the project. The survey sampling plan used for the surveys was developed in accordance with NHTSA guidelines and formally approved by NHTSA. The original plan was modified once to accommodate pickup trucks in the sample. The surveys were conducted by the Social Science Research Center at Mississippi State University for the Mississippi Office of Highway Safety. The Seat Belt/Motorcycle Helmet Survey for Mississippi uses a multistage area probability approach. In the first stage, an appropriate number of sampling units are randomly selected. The primary sampling unit for the Mississippi survey is the county. The least populated counties, approximately 15% of the State’s population, are excluded from the sampling process. The survey was conducted in 16 Mississippi Counties containing approximately 46% of the State’s population. These counties can be seen in Figure 2.

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Figure 2: Mississippi counties chosen for Seat Belt Surveys in 2002

Summary of Sampling Methodology I.

Three counties were selected as certainty counties because of having populations much larger than other Mississippi Counties. The certainty counties were Harrison, Hinds, and Jackson. Thirty-two of the least populated counties, whose combined population accounted for only 15% of the state’s population, were eliminated from sampling.

III.

Sampling was done with replacement. In addition to the 3 certainty counties, 13 other counties were chosen, thus the sample consists of 16 counties.

IV.

The sample includes 409 forty-minute observation periods. The 3 certainty counties were allotted 28 observation periods each, while the remaining 13 counties were allotted 25 observation periods each.

V.

The Mississippi Department of Transportation (MDOT) provided information for all road segments having an Average Daily Travel (ADT) equal to or exceeding 500 miles. Through a random variable generated by the computer program Statistical Program for the Social Sciences (SPSS), all road segments in each of the counties were randomly selected.

VI.

The roads were then sorted by county and functional road classification. The functional road classifications for each road segment were re-coded into six functional classes.

VII.

The number of observation periods per road classification per county was calculated using Total Vehicle Miles Traveled (VMT) and ADT criteria. Total VMT for each county were calculated by multiplying ADT for each segment to the corresponding road segment lengths. A similar statistic was calculated for each of the functional road classes. This figure was divided by the total county VMT and then multiplied by the number of observation time periods allotted for each county. For example, there are 3,860 road segments in Hinds County with a VMT of 5,905,627.26 miles. Functional road Class 1 had a VMT of 640,676 miles. The 4

640,676 was then divided by 5,905,627.26 equaling 0.1084857, which was in turn multiplied by 28, or the number of observation periods allotted to Hinds County. Thus 3.0375991, or three observation periods were allotted to Class 1 roads in Hinds County. The first three randomly sorted segments from road Class 1 in Hinds County were chosen for the sample. In the same manner, segments for each road class in each county were chosen to be observation locations in the study. VIII.

All road segments were randomly selected and sorted by functional class. The number of roads to be sampled in each class was selected in the order that they were chosen in the random sampling process. For example, if Hinds County needed to sample three Class 1 roads, the first three Class 1 roads plus several back up selections were chosen. The “TP” number or location designation was then sent to MDOT to be placed on maps and sent back to Mississippi State.

IX.

For observational convenience and efficiency, sites for each county were clustered according to geographical proximity.

X.

For each cluster a day of the week was randomly chosen. All days of the week were eligible for selection. However, once a day had been chosen, it was no longer available for the remaining sites in that particular county.

XI.

Once a site was assigned a day of the week, observation times between 8:00 a.m. and 6:00 p.m. were randomly chosen in hourly increments for each site. One hour for lunch was randomly chosen of the hours from 11:00 a.m. to 2:00 p.m.

XII.

Direction of traffic observation was randomly assigned for all 409 sites using random assignment procedure generated by SPSS.

XIII.

Observers were instructed to observe from a site using the assigned direction for a period of 40 5

minutes. Interstate sites were surveyed on off-ramps. XIV.

The sampling frame includes counting all passenger vehicles, sports utility vehicles, vans, and pickup trucks not exempted by state law. Two observers are used at each observation site. One observer counts the driver and outside passengers on the front seat of passenger cars, sport utility vehicles, and vans. The other observer counts the driver and outside passenger in pickup trucks.

Further details on the sampling methodology of the survey “DOCUMENTATION OF MISSISSIPPI OBSERVATIONAL SURVEYS OF SEAT BELT AND MOTORCYCLE HELMET USE” prepared by Dr. Stephen H. Richards, Director, Transportation Center, University of Tennessee; and Dr. Tommy Wright, Adjunct Professor of Statistics, University of Tennessee. They can be obtained from the Social Science Research Center at Mississippi State University, Box 5287 Mississippi State, MS 39762, or by calling Mr. Jim Landrum at 662-325-7962.

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2002 Statewide Safety Belt Survey Results The results of the surveys performed this year shows the 2002 Click It or Ticket Campaign had a positive impact on Mississippi’s seat belt usage rate. As can be seen in Figure 3, this year’s usage rates climbed from 54% in the baseline survey to 62% in the follow-up survey. This increase is an improvement of 14.8% from the 2002 baseline figure. The margin of error for both surveys at a 95% probability is less than 4%. Figure 3: 2002 Seat Belt Usage Rates Baseline and Follow-up Statewide Surveys Sites Surveyed = 409

70% 60% 50% 40%

62% 54%

30% 20% 10% 0% Source: Social Science Research Center, Mississippi State University

Baseline

Follow-up

Similar to last year’s survey, belt usage rates increased across the board by type of road segment observed. Figure 4 illustrates the percentage increases (from baseline to follow-up) for all six types of road classes from busy urban interstates to less traveled rural local roads. For a second year in a row, major rural roads increase the most with a 10% increase from baseline to follow-up while urban local roads increase only 5% during the campaign.

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Figure 4: Belt Usage by Type of Road 2001 MS Click It or Ticket Telephone Survey Percentage Increases in Seat Belt Usage from Baseline Survey to Follow-Up Survey by Type of Road

6%

Rural Interstates

10%

Rural Major Roads

9%

Rural Local Roads

6%

Urban Interstates

7%

Urban Major Roads

5%

Urban Local Roads 0%

5%

10%

Source: Social Science Research Center, Mississippi State University

Although the figures indicate seat belt usage rates increased during the time frame between surveys this year, the 2002 figures do not appear as impressive as the results of 2001 surveys. The seat belt count of 62% is the same for the 2001 and 2002 follow-up surveys. However, in 2001 the baseline usage rate was 49% compared to the 54% baseline count in 2002. This translates into a 26% increase in usage rate for 2001 and a 15% increase in usage rate for 2002. On the other hand, the 2002 results also show a 5% increase of “sustainability of use” for Mississippians buckling up from the baseline of 2001 to the baseline of 2002. Figure 5 and Figure 6 illustrate the 2001 and 2002 figures relating to percentage differences and percentage increases from baseline to follow-up surveys.

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Figure 5: Percentage Differences in Belt Usages 2001 & 2002 MS Pre and Post Click It or Ticket Surveys 2%3%

Harrison Yazoo Lee Scott Lowndes Madison Hinds Leflore Jackson Lamar Simpson Warren Lauderdale Rankin Bolivar Desoto

6%

8% 9% 9%

15%

9%

1%

Percentage differences in Seat Belt Usages from Pre to Post Surveys

9%

6%

11%

8%

2002 2001

13%

11%

13%

6%

15%

8%

15%

7%

16%

1%

17%

2%

18%

5%

19%

2%

25%

19%

0%

5%

10%

15%

29%

20%

25%

30%

Figure 6: Percentage Increases in Belt Usages 2001 & 2002 MS Pre and Post Click It or Ticket Surveys Harrison Yazoo Lee Scott Lowndes Madison Hinds Leflore Jackson Lamar Simpson Warren Lauderdale Rankin Bolivar Desoto

7% 4% 11% 16% 20% 21%

9%

16% 19% 14% 23% 29%

11% 14%

2002 2001

45%

31% 29%

36% 33%

1%

0%

43%

25%

2%

Percentage increases in Seat Belt Usages from Pre to Post Surveys

29%

4%

18%

7%

35%

5%

89%

37%

20%

65%

40%

60%

9

80%

100%

The percentage differences are calculated by subtracting the baseline usage rates from the follow-up rates [Example: 2002 Follow-up Harrison – 2002 Baseline Harrison = 49% – 46% = 3%]. As can be seen in Figure 5, Harrison and Scott counties are the only counties with higher percentage differences in 2002 than in 2001. However, Harrison County’s usage rates are lower than those recorded last year. Also between 2001 and 2002, significant negative contrasts in the usage rate differences for Lowndes, Jackson, Simpson, Warren, Lauderdale, Rankin, and Bolivar counties contribute to the minimal statewide usage rate difference for 2002 (+8). The percentage increases for 2001 and 2002 in Figure 6 are calculated by taking the results in Figure 5 and dividing each result by the baseline figure for the associated county and year [Example: (2002 Follow-up Harrison – 2002 Baseline Harrison ) ÷ 2002 Baseline Harrison = (49% – 46%) ÷ 46% = 7%]. The most dramatic shift recognizable in Figure 6 is the change for Bolivar County. Bolivar had a percentage increase of 89% for 2001 compared to a 5% increase in 2002. Similar to the percentage differences in Figure 5, the percentage increases in Figure 6 are much higher for 2001. However, again it is Scott County deserving commendations for an extremely significant belt usage increase in 2002. To compare these two years at another level, Figure 7 depicts the differences in baseline figures and follow-up figures between the two years [Example: 2002 Baseline Harrison – 2001 Baseline Harrison = 46% - 52% = -6%].

These data give an indication to the counties that had success in belt usage

sustainability between the two years. Rankin (+13%) and Bolivar (+10%) counties had the highest baseline sustainability, but Warren (-18%) and Bolivar (-13%) showed less favorable figures in the follow-up comparisons. A majority of the baseline differences between the two years are positive, which is a good indication of Mississippi’s progress in the “drive to save lives” by continuing to buckle-up. 10

Figure 7: Sustainability of Belt Usage 2001 & 2002 MS Click It or Ticket Surveys Harrison Yazoo Lee Scott Lowndes Madison Hinds Leflore Jackson Lamar Simpson Warren Lauderdale Rankin Bolivar Desoto

-5% -6%

5% 3% 3% -1% -2%

5% 6%

2%

7%

2% -4%

6% 7%

9%

Follow-up 2002 minus Follow-up 2001

5%

-2% -18%

Percentage differences in survey results from 2001 to 2002 survey

7%

0%

-1%

5%

Baseline 2002 minus Baseline 2001

-2% -6%

9%

-1%

13%

-13%

10%

-3%

-20%

-10%

7%

0%

10%

20%

The two major messages brought forth by Figures 5 through 7 are the lack of usage increases by county from 2001 to 2002 and the substantial sustainability of baseline usage rates from 2001 to 2002. The fact that usage rates did not increase as much as they did last year

is

offset

by

a

Figure 8: Confidence Intervals considerably higher baseline

Weighted Seat Belt Counts 2001 – 2002 Baseline and Post Click It or Ticket 95% Confidence Intervals

in Baseline 2001

49% +/- 3.32%

representation

Post 2001

62% +/- 3.74%

Baseline 2002

Figure

Post 2002 50

52

54

56

58

60

62

64

of

visual this

8

along

with

confidence intervals to show

62% +/- 3.59% 48

A

phenomenon is presented in

54% +/- 4.41%

46

2002.

66

overlap and calculated error.

Percent

11

The following table provides a county-by-county breakdown of seat belt use in the 2001 and 2002 pre and post surveys in weighted count by county. The survey results listed in this table were used to produce all graph information in Figures 5 through 8.

2001-2002 County-by-County Weighted Seat Belt Counts for Baseline and Follow-up Surveys

County

Baseline Weighted (%) 2001

Post Survey Weighted (%) 2001

Baseline Weighted (%) 2002

Post Survey Weighted (%) 2002

Bolivar

28

53

38

40

Desoto

44

73

51

70

Harrison

52

54

46

49

Hinds

52

64

58

66

Jackson

49

64

54

60

Lamar

52

67

57

65

Lauderdale

48

65

57

59

Lee

42

51

45

54

Leflore

29

42

38

49

Lowndes

55

64

61

62

Madison

57

68

64

70

Rankin

55

74

68

73

Scott

36

45

35

50

Simpson

48

64

47

64

Warren

58

75

56

57

Yazoo

49

57

56

62

Total

49 ±3.32

62 ± 3.74

54 ±4.41

62± 3.59

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The contrast and comparison of the figures from the 2001 and 2002 campaigns show that 2002 was not as productive a year as 2001 with respect to raising seat belt usage rates to a higher bar. At a 62% usage rate, Mississippi is 13% off the 2002 national usage rate of 75%. Whether it is more effective media campaigns, stricter enforcement, or some other form of belt use encouragement, Mississippi will need to set its sights higher to approach this nationwide figure in the future.

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2002 Statewide Motorcycle Helmet Survey Results The final segment to be discussed concerns the Motorcycle Helmet Use in Mississippi. As a part of the Seat Belt Survey, Motorcycle Helmets are also counted. Mississippi is fortunate to have an excellent Motorcycle Helmet law. All motorcycle riders must wear helmets or receive a ticket. Motorcycle Helmet use is over 98 % in Mississippi. Thus, there is little room for improvement in helmet use. Motorcycle Helmet Usage Rates for 2002 In the baseline sample helmet use was 97.98% (+/-) 2.86 and that figure improved slightly to 98.76% (+/-) 2.27 in the follow-up survey.

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Mississippi Seat Belt/Motorcycle Helmet Surveys 2002 Survey Facts

•

Official statewide seat belt use in baseline survey was 54% ± 4.41.

•

Official statewide seat belt use in post survey was 62% ± 3.59.

•

All survey counties increased in belt use in the post project survey, both in per person observations and in the weighted percentage.

•

Highest increases occurred in Scott (43%), Desoto (37%), Simpson (36%), Leflore (29%), and Lee (20%) counties.

•

Lowest increases occurred in Hinds (14%), Lamar (14%), Jackson (11%), Yazoo (11%), Madison (9%), Harrison (7%), Rankin (7%), Bolivar (5%), Lauderdale (4%), Lowndes (2%), and Warren (1%) counties.

•

Seat belt use increased on all types of roads: Rural Interstates (9%), Rural Major Roads (18%), Rural Local Roads (18%), Urban Interstates (11%), Urban Major Roads (10%), Urban Local Roads (8%).

•

Seat belt use increased in both cars (15%), and pickup trucks (11%).

•

Seat belt use in cars (follow-up survey) was 65.64% (+/-) 4.57.

•

Seat belt use in trucks (follow-up survey) was 52.57% (+/-) 2.93.

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REFERENCES

U.S. Department of Transportation Press Release, September 9, 2002 (http://www.nhtsa.dot.gov). Buckle Up America Faith Community Leader Safety Facts, 2002 (http://www.nhtsa.dot.gov) NHTSA Occupant Protection Division – Winter 2002 (http://www.nhtsa.dot.gov) Documentation of Mississippi Observational Surveys of Safety Belt and Motorcycle Helmet . Dr. Stephen H. Richards, Transportation Center the University of Tennessee and Dr. Tommy Wright, Adjunct Associate Professor of Statistics, The University of Tennessee. Can be obtained from the Social Science Research Center, Box 5286, Mississippi State University, Mississippi State, MS 39762, Contact James W. Landrum.

B e f o r e and A ft e r S ta e w id e S u rv e y

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