Seatbelt law enforcement and motor vehicle crash fatalities among blacks and whites in Louisiana and Mississippi.

Background: Seatbelt laws save lives. Primary enforcement (allowing citations solely for seatbelt nonuse) is a more effective means of saving lives, yet seven southern states have no primary laws, due in part to concern about racial profiling.

Methods: Non-Hispanic, black:white (B:W), occupant motor vehicle crash mortality rate ratios (MRRs) were compared across the 15 to 64 age range over two time periods in two demographically comparable southern states (Louisiana and Mississippi).

Results: From 1992 to 1994 (when neither state had primary law) to 1996 to 1998 (when Louisiana had primary law) B:W MRRs were 0.73 (95% confidence interval = 0.61, 0.88) and 0.72 (0.60, 0.86) in Louisiana and 1.01 (0.9, 1.12) and 1.22 (1.10, 1.35) in Mississippi.

Conclusions: Successful opposition to primary seat belt enforcement may have the unintended effect of producing racial disparities in motor vehicle crash mortality that adversely affects blacks.

Key Words: motor vehicle crash fatality, race, injury prevention, legislation

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Motor vehicle crashes are a leading cause of preventable morbidity and mortality in the US, accounting for more than 44,000 fatalities, 3 million nonfatal injuries, 290,000 hospitalizations, and 3.4 million emergency department visits annually. (1-4) Safety belts are the single most effective way to reduce fatal injury from motor vehicle crashes, and have saved hundreds of thousands of lives over the past three decades. (4, 5) However, this public health success has largely been attributable to the enforcement of state seatbelt laws. Before the passage of the first state seatbelt enforcement law in 1984, seatbelt use among US motorists was 11%. (6) Since then, it has climbed to 80%. (7)

While seatbelt laws increase seatbelt usage, their effectiveness varies by type of enforcement. Primary laws, which allow law enforcement officers to stop and cite motorists solely for nonuse of seatbelts, are more effective than secondary laws, under which motorists can be cited for seatbelt law violations only after being stopped for another offense. (4, 8-11) Specifically, Rivara et al. (8) found that eight of nine studies assessing the impact of primary laws on motor vehicle crash mortality showed a decrease, while the US Preventive Services Task Force Guide to Community Preventive Services accepted evidence showing a 3.1% to 13.9% drop in motor vehicle crash fatalities per vehicle-mile traveled. (4, 9-11) Nevertheless, only 21 states and the District of Columbia have primary laws covering adults. (7) Of these, eight states (Delaware, GA, LA, MD, NC, OK, TN, TX) plus the District of Columbia come from one of the 16 geographic areas classified as southern by the US Census Bureau; (12) while Arkansas, Florida, Kentucky, Mississippi, South Carolina, Virginia, and West Virginia have secondary laws. (7) The failure of many southern states to pass primary legislation is of particular importance because the per capita motor vehicle crash mortality in the South is 37% higher than the rest of the nation. (13) Moreover, the disproportionate numbers of black motorists in the South magnifies the potential number of lives that might be saved with greater southern participation, because motor vehicle crash mortality among blacks is generally higher than among whites, due, in part, to lower seatbelt use, as well as factors related to lower socioeconomic status. (14)

One barrier to the passage of primary seat belt laws is concern about racial implications, particularly racial profiling. (4) Concerns about racial profiling have not been supported by data from studies focusing on the impact of primary seat belt laws in the South (15, 16) or elsewhere, (17) but limited data do suggest that motorists who are members of minority racial/ethnic groups are more responsive to the enforcement of primary laws than their white counterparts. (18-21) To our knowledge, however, there are no published data indicating that this has impacted the black: white disparity in motor vehicle crash mortality.

The failure of many southern states to pass primary laws produces a milieu for field (or natural) experiments to examine this question at the level of comparable aggregate populations. In natural experiments, comparable populations, in this case the populations of entire states, voluntarily assign themselves different levels of risk. (22) In the present report, we use this approach to explore motor vehicle crash mortality among blacks and whites in two contiguous and demographically comparable southern states, Louisiana (LA) and Mississippi (MS). Louisiana passed primary legislation in 1995, while Mississippi has never passed primary legislation for adults. This is consistent with the relative positions of the two states with respect to seatbelt use. Specifically, in 2004, MS (63.2% use) was tied for 51st among all states plus the District of Columbia, while LA (75%) ranked 39th. (7)

Materials and Methods

Study Design: In a natural experiment, motor vehicle crash mortality among blacks and whites was compared in Louisiana and Mississippi over two 3-year time periods: 1992 to 1994 and 1996 to 1998. The 3-year period from 1992 to 1994 was immediately before passage of legislation mandating primary enforcement of seatbelt laws in Louisiana, which went into effect September 1, 1995. During 1992 to 1994, both LA and MS had secondary enforcement of state seatbelt laws. The 3-year period from 1996 to 1998 was immediately after primary legislation went into effect in LA. During this time, MS continued with secondary enforcement of its state seatbelt law. LA and MS were selected for analysis because they have the greatest proportion of black residents. To underscore overall demographic comparability, data from Census 2000 (23) were used to compare both states across measures of age structure, socioeconomic status, racial composition and population density.

Outcome Measure: State-specific motor vehicle crash mortality rates for non-Hispanic blacks and non-Hispanic whites ages 15 to 64 in LA and MS were compared across 1992 to 1994 and 1996 to 1998 using two measures: 1). Race-and age-specific mortality rates per 100,000 population; and 2). Black:white mortality rate ratios (MRR), which were calculated as the age-specific and age-standardized mortality rates among blacks divided by the corresponding mortality rates among whites. Approximate 95% confidence intervals for MRRs were calculated using StatsDirect software (Cheshire, United Kingdom). (24, 25)

Data Source: Motor vehicle crash mortality data were obtained from WISQARS (Web-based Injury Statistics Query and Reporting System) which is maintained by the National Center for Injury Prevention of the Centers for Disease Control. (25) WISQARS is an interactive database system that provides customized reports of injury-related data. Data were limited to ICD-9 E codes for traffic crash fatalities involving occupants of motor vehicles (ICD-9 Codes: E810-E819 [0.0, 0.1)] Because coding of mortality data changed significantly in 1999, as a result of the transition from ICD-9 to ICD-10, the analysis was limited to mortality data through 1998.

Results

The demographic comparability of the two states is shown (Table 1) by similar values in the year 2000 census for percentage of the population under 5 years (7.2% MS and 7.1% LA), under 18 years (27.3% and 27.3%), over 65 years (57.7% and 57.6%), the percentage of white (61.4% and 63.9%), and black (36.3% and 32.5%), the percentage > 5 years of age living in the same household in 1995 and 2000 (58.5% and 59%), the percentage of high school graduates (72.9% and 74.8%), bachelor's degree graduates or higher in persons 25 and older (16.9% and 18.7%), mean travel time to work (24.6 min and 25.7 min), persons per household (2.63 and 2.62) and percent below poverty in 1999 (19.9% and 19.6%). Per capita income ($15,583 and $16,912) was about 10% higher in LA, although both states are well below the national average of $21,587. Also, 9.2% of persons age 5+ years speak a language other than English at home in LA (versus 3.6% in MS) and the number of persons per square mile is higher in LA (102.6 versus 60.6) and overall age-standardized.

Table 2 shows race- and state-specific mortality rates for occupants of motor vehicles among non-Hispanic persons aged 15 to 64 in Mississippi and Louisiana during 1992 to 1994 (when both states had secondary laws), and 1996 to 1998 (when LA had a primary law for adults and MS had a secondary law). In each period, rates for MS blacks were higher than those for LA blacks and rates for MS whites were higher than those for LA whites.

Figure 1a-d shows age-specific (5-year age groups) non-Hispanic black:white mortality rate ratios for motor vehicle occupant mortality in MS (1a and b) and LA (1c and d) in 1992 to 1994 and 1996 to 1998. Rate ratios held steady in LA, with none of the lower boundaries for the 95% being above 1.00 (equality) in either period and the overall rate ratio being significantly under 1.00 in both. In contrast, while there were no rate ratios significantly greater than 1.00 in MS in 1992 to 94, five of the six age groups from 25 to 54 years were significantly above equality in 1996 to 98, and the state as a whole had moved from a position of 1.01 (95% confidence interval (CI) 0.9, 1.12 = not significantly different from equality) to 1.22 (95% CI 1.10, 1.35 = significant inequality). Meanwhile, in Louisiana, the overall rate ratios remained nearly the same, with both showing a significant advantage for blacks of 0.73 (95% CI 0.61, 0.88) in 1992-94 and 0.72 (95% CI 0.60, 0.86) in 1996 to 98. From a somewhat different perspective, it is seen that while the rate ratios for MS in 1992 to 94 versus 1996 to 98 and for LA in 1992 to 94 versus 1996 to 98 were not significantly different from each other in either state across time periods, the net change in MS (+0.21 from 1.01-1.22) was more than 20 times greater than the net change in LA (-0.01 from 0.73-0.72).

[FIGURE 1 OMITTED]

Discussion

These results are consistent with the hypothesis that successful opposition to primary law may have had the unintended effect of permitting black:white racial inequalities in motor vehicle crash mortality, adversely affecting blacks. Specifically, in 1992 to 94, when both MS and LA had a secondary law, the MS black:white mortality rate ratio was not significantly different from 1.00 (equality), while in LA, blacks had a significantly lower risk than whites. However, in 1996 to 98, when LA had passed a primary law while MS remained a secondary state, the MS black:white rate ratio became significantly different from 1.00, while LA remained stable. In net, the black:white mortality rate ratio increase in MS (+0.21) was more than twenty times higher than that for LA (-0.01).

From a different perspective, the results did not show a significant change in black:white mortality rate ratio from one time period to the next in either state. This illustrates the complexity of attempting to interpret "natural" as compared with investigator-controlled experiments. While one interpretation from this perspective could be that passage of primary law in LA had no effect on the black:white mortality rate ratio, it is also possible that the effect of the law in LA was to keep LA stable. While these data cannot tell what might have happened in MS if it, too, had passed a primary law, the increased sensitivity of blacks to such legislation (18-21) makes it tempting to speculate that the state would at least have come closer to retaining its position of relative equality. Finally, while MS and LA are demographic peers, and both had black:white mortality rate ratios whose 95% confidence intervals included equality in 1992 to 94, the considerably higher absolute mortality rates in MS throughout suggests that additional factors, most probably relating to physical and cultural environmental differences, are also highly important in explaining the differences between the two states.

The problem of motor vehicle crash mortality is of particular concern in the South, because of a 37% excess in per capita motor vehicle mortality as compared with the rest of the nation. (13) In part, this may be due to a greater distance between hospitals in the South. (13) Failure to pass primary safety belt laws covering adults in seven southern states, however, may also contribute.

In addition to libertarian concerns, passage of primary legislation has been hampered by expectations that blacks would be more likely to be cited for failure to wear seat belts because of racial profiling. (4) Regarding the latter, data from the National Highway Traffic Safety Administration (27) and the US Department of Justice (28) show that blacks are more likely to be stopped for traffic-related reasons than whites, even though studies focusing on primary law fail to confirm racial profiling in this particular context. (15-17) In part, perceptions of racial profiling may fuel greater improvements in seatbelt use among African Americans and other ethnic groups relative to whites when primary laws are passed. (19-22) The likely persistence of mistrust would suggest that in addition to primary law, there is a need for companion programs that provide strong, culturally sensitive interventions promoting safety belt use among African Americans and other racial/ethnic groups based on the actual benefits of that behavior, rather than the fear of police interaction.

Finally, while these are population data, they have applicability for clinicians in at least two ways. First, physicians can participate in community systems that address health problems that require community-level action, can act as consultants for communities implementing crash prevention programs or introducing legislation and can serve as advocates to initiate and maintain effective programs. (29) Second, health care providers have an important role as prevention educators and counselors to individual patients on the matter of motor vehicle safety (30) and may find the present information useful in helping to shape those interactions.

These data are limited in the sense that temporal associations between the emergence of disparity and differences in primary and secondary seat belt law as observed in the death certificate data are ecologic. While they are consistent with the hypothesis that the observed associations may have been due to individual differences in seat belt use, they cannot confirm or deny that hypothesis.

In summary, since there was a demonstrable change in the mortality equality for black and white Mississippi residents following failure to pass the primary seatbelt law, these data should provide a caution to policy makers seeking to address racial concerns about profiling by opposition to primary law. Under such circumstances, they might agree that passage of antiharassment legislation and provision for positive, culturally sensitive, community-based interventions along with primary enforcement laws are a more prudent approach.

References

1. National Center for Injury Prevention and Control Working to prevent and control injury in the United States: fact book for the year 2000. Atlanta, GA: Centers for Disease Control and Prevention, 2000.

2. Centers for Disease Control and Prevention. Web-based Injury Statistics Query and Reporting System (WSQARS). Available at: http://www.cdc.gov/ncipc/wisqars. Accessed January 4, 2006.

3. National Highway Traffic Safety Administration safety facts, 2002: a compilation of motor vehicle crash data from the Fatality Analysis Reporting System and the General Estimates System. Washington, DC: US Department of Transportation, National Highway Traffic Safety Administration, 2002. DOT HS 809 446.

4. Task Force on Community Preventive Services. Motor-vehicle occupant injury: strategies for increasing use of child safety seats, increasing use of safety belts, and reducing alcohol-impaired driving. MMWR Recommendations and Reports 2001;50 (RR07):1-13.

5. National Highway Traffic Safety Administration. Traffic safety facts 2002: occupant protection. Washington, DC: US Department of Transportation, National Highway Traffic Safety Administration, 2002, DOT HS 809 610.

6. Department of Transportation. National Highway Traffic Safety Administration. Traffic Safety Facts 1996. 1997, 808-649.

7. Glassbrenner D. Safety belt use in 2004--Use rates in the states and territories. Traffic Safety Facts. Research Note, 2004, DOT HS 809 813.

8. Rivara FP, Thompson DC, Cummings P. Effectiveness of primary and secondary enforced seat belt laws. Am J Prev Med 1999;16(1 Suppl): 30-9.

9. Waagenar AC, Maybee RG, Sullivan KP. Mandatory seat belt laws in eight states:a time-series evaluation. J Safety Res 1988;19:51-70.

10. Evans WN, Graham JD. Risk reduction or risk compensation? The case of mandatory seat belt laws. J Risk and Uncertainty 1991;4:61-73.

11. Winniki J. Safety belt use laws: evaluation of primary enforcement and other provisions. Washington, DC: Department of Transportation National Highway Traffic Safety Administration, 1995, DOT HS 808 324.

12. US Census Bureau. Census 2000. Appendix A. Geographic terms and concepts. Available at: http://www.census.gov/geo/www/tiger/glossry2.pdf. Accessed May 9, 2005.

13. Clark DE, Cushing BM. Predicting regional variations in mortality from motor vehicle crashes. Academic Emergency Medicine 1999;6:125-130.

14. Braver ER. Race, Hispanic origin, and socioeconomic status in relation to motor vehicle occupant death rates and risk factors among adults. Accid Anal Prev 2003;35:295-309.

15. Preusser DR, Preusser CW. Evaluation of Louisiana's safety belt law change to primary enforcement. Washington, DC: US Department of Transportation, National Highway Traffic Safety Administration. 1997, DOT HS 808 620.

16. Solomon MG, Nissen WJ. Evaluation of Maryland, Oklahoma, and The District of Columbia's seat belt law change to primary enforcement. Washington, DC: US Department of Transportation, National Highway Traffic Safety Administration, 2000, DOT HS 809 213.

17. Eby DW. Vivoda JM, Forcyce TA. The effects of standard enforcement on Michigan safety belt use. Accid Anal Prev 2002;34:815-823.

18. Martin M, Leonard M, Allen S, et al. Commentary: using culturally competent strategies to improve traffic safety in the black community. An Emerg Med 2004;44:414-418.

19. Davis JW, Bennink L, Kaups KL, et al. Motor vehicle restraints: primary versus secondary enforcement and ethnicity. J Trauma 2002;52:225-228.

20. Reinfurt DW. Campbell BJ, Stewart JR, et al. North Carolina's occupant restraint law: a three year evaluation. Chapel Hill, University of North Carolina Highway Safety Research Center, 1988, UNC/HSRC-88/10/5.

21. US Department of Transportation, National Highway Traffic Safety Administration. Highway safety needs of US Hispanic communities: issues and strategies. Washington, DC: National Highway Traffic Safety Administration, 1995, DOT HS 808 373.

22. Hennekens CH, Buring JE. Epidemiology in Medicine. Boston, Little Brown, 1987.

23. FedStats. Available at: http://www.fedstats.gov. Accessed May 9, 2005.

24. Armitage P, Berry G, Matthews JNS. Statistical Methods in Medical Research, 4th ed. Oxford, Blackwell Science, 2002.

25. Newman SC. Biostatistical Methods in Epidemiology. New York, John Wiley & Sons, 2001.

26. Centers for Disease Control and Prevention, National Centers for Injury Prevention and Control. Web-based Injury Statistics Query and Reporting System (WISQARS) [online]. Available at: http://www.cdc.gov/ncipe/wisqars. Accessed January 4, 2006.

27. National Highway Traffic Safety Administration. 1998 Motor Vehicle Occupant Safety Survey. Available at: http://www.nhtsa.dot.gov/people/injury/research/safetysurvey/1998_Vol3/CSSR_Index.hti. Accessed August 19, 2004, per Citation 18.

28. US Department of Justice Statistics. Contacts between police and the public, 1999. Available at: http://www.ojp./gov/bjs/pub/pdf/cpop99.pdf. Accessed August 19, 2004 per Citation 18.

29. United States Preventive Services Task Force. Guide to Clinical Preventive Services, 2nd ed, 1996. Available at: http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=hstat3.section.10513. Accessed May 3, 2005.

30. Ellis HM, Nelson B, Cosby O, Morgan L, et al. Achieving a credible health and safety approach to increasing seat belt use among African Americans. J Health Care Poor Underserved 2000;11:144-50.</p> <pre> Vitality shows in not only the ability to persist but the ability to start over. --F. Scott Fitzgerald </pre> <p>Robert S. Levine, MD, Nathaniel C. Briggs, MD, MSC, David G. Schlundt, PHD, Nathan Stinson Jr., MD, PHD, MPH, Rueben C. Warren, DDS, DRPH, and Irwin A. Goldzweig, MS

From the National Center for Primary Care, Department of Community Medicine/Preventive Medicine, Morehouse School Of Medicine, Atlanta, GA; the Department of Family & Community Medicine, Division of Preventive Medicine, Meharry Medical College, Nashville, Nashville, TN; and the Department of Psychology, Vanderbilt University School of Medicine, Nashville, TN.

Reprint requests to Robert S. Levine, MD, National Center for Primary Care. Department of Community and Preventive Medicine, Morehouse School of Medicine, 720 Westview Drive SW. Atlanta, GA 33010. Email: [e-mail]

Financial support from the Meharry State Farm Alliance, Office of Minority Health/Centers for Medicare and Medicaid Services.

Accepted October 4, 2005.

RELATED ARTICLE: Key Points

* Primary enforcement of state seatbelt laws (i.e., motorists can be cited solely for violating a seatbelt law) saves more lives than secondary enforcement (i.e., motorists can be cited for nonuse of seatbelts only after being stopped for another violation).

* Concerns about differential enforcement (racial profiling) have been a major barrier to passage of primary law legislation in the South and elsewhere.

* We compared state-specific mortality among blacks and whites in the context of a natural experiment characterized by a primary law state (Louisiana) that was geographically contiguous with, and demographically comparable to, a secondary law state (Mississippi).

* Louisiana's passage of a primary law, in combination with Mississippi's failure to do so, was associated with a significantly lower black:white motor vehicle crash mortality disparity in Louisiana, and reciprocally, a significantly higher black:white motor vehicle crash mortality disparity in Mississippi.

* Successful opposition to primary seat belt laws may have the unintended effect of worsening racial disparities in mortality.

Table 1. Demographic characteristics of Mississippi and Louisiana
(1999-2000)

Population characteristic                     Louisiana     Mississippi

Total population                              4,468,976     2,844,658
Percent < 5 years of age                              7.1%          7.2%
Percent < 18 years of age                            27.3%         27.3%
Percent > 65 years of age                            11.6%         12.1%
Percent female                                       51.6%         51.7%
Percent white                                        63.9%         61.4%
Percent black                                        32.5%         36.3%
Percent of persons age 5+ years living in            59.0%         58.5%
  same house in 1995 and 2000
Percent Hispanic or Latino origin                     2.4%          1.4%
Percent home language other than English              9.2%          3.6%
Percent high school graduates (25+ years of          74.8%         72.9%
  age)
Percent bachelor's degree (25+ years of age)         18.7%         16.9%
Mean travel time to work                             25.7          24.6
                                                   minutes       minutes
Persons per household                                 2.62          2.63
Per capita money income                         $16,912       $15,853
Percent below poverty                                19.6%         19.9%
Persons per square mile                             102.6          60.3

Table 2. Race-specific mortality rates among non-Hispanic motor vehicle
occupants 15-64 years of age in Louisiana and Mississippi before and
after passage of primary seatbelt legislation in Louisiana in 1995

                                  Louisiana
                 No. of deaths  Population   Crude death rate

1992-94  Blacks       154       2,513,217         6.13
         Whites       454       5,532,575         8.21
1996-98  Blacks       165       2,701,311         6.11
         Whites       465       5,611,841         8.29

                                  Mississippi
                 No. of deaths  Population  Crude death rate

1992-94  Blacks       548       1,746,567        31.38
         Whites       989       3,269,178        30.25
1996-98  Blacks       652       1,905,758        34.21
         Whites       936       3,397,361        27.55