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Impact of Safety-Belt Use on Motor-Vehicle Injuries and Costs -- Iowa, 1987-1988

Each year in the United States, motor-vehicle-related trauma results in approximately 40,000 deaths, 5.4 million nonfatal injuries, and $15.4 billion in direct medical costs and costs of emergency services (1,2). The use of safety belts reduces the number and severity of injuries from motor-vehicle crashes, and since states began enacting safety-belt laws, the prevalence of safety-belt use in the United States has increased substantially (3). In Iowa, where a safety-belt use law was enacted in 1986, the observed rate of safety-belt use increased from 18% in 1985 to 55% in 1988 (4). Data from the Iowa Safety Restraint Assessment were used to estimate the effect of this increase on injury severity and hospital costs and to estimate the statewide savings in direct costs (i.e., hospital and professional fees) and indirect costs (i.e., administrative costs and loss of productivity) for 1 year (5). This report summarizes the findings of this study.

The Iowa Safety Restraint Assessment was conducted by the Iowa Methodist Medical Center from November 1, 1987, through March 31, 1988. Data were gathered on injured motor-vehicle occupants treated at nine urban (population: greater than 50,000 persons each) and seven rural hospital emergency departments located in all regions of Iowa. Emergency department nurses conducted interviews with patients or obtained information from other sources (e.g., witnesses, ambulance personnel, or police on the crash scene) when patients were unable to answer questions because of severe injury or alcohol intoxication. Persons were asked about safety-belt use at the time of the crash, vehicle type and speed, type of crash (e.g., head-on or rear-end), and position of person(s) in the vehicle. Alcohol use was defined as a blood alcohol content of greater than or equal to 0.01 g/dL or documented clinical suspicion of alcohol use in the medical record. The hospitals provided data on hospital charges and estimated payments by source (i.e., private insurance, Medicare, Medicaid, and self-pay {uninsured}). Analyses were restricted to persons subject to the provisions of the safety-belt use law (i.e., front-seat occupants aged greater than or equal to 6 years) and to the 11 hospitals that provided cost data. Costs associated with injuries for each participating hospital were calculated by multiplying its charges by the average percentage of charges collected from each source of payment. The projected annual statewide savings in direct and indirect costs for 1 year were based on a comparison between estimates of actual costs for the study population and expected costs if safety-belt use in Iowa remained at 18% (5).

During the 5-month period, 997 patients met the criteria for inclusion in the study. The overall prevalence of safety-belt use at the time of crash among the case-patients was 50.5%. The mean age for nonbelted persons (n=494) was significantly lower than that for belted persons (n=503) (28.2 years versus 34.9 years {p less than 0.001}). Nonbelted occupants were more likely to be male, have consumed alcohol, have been in a head-on or rollover crash, have had higher injury severity scores (p less than 0.001), have been hospitalized (25.6% versus 7.6% {p less than 0.001}), have been permanently disabled (2.0% versus 0.2% {p=0.005}), or have died in the hospital (0 versus 2.0% {p=0.001}).

Nonbelted persons accounted for 78% of hospital costs. Although most injured persons had private insurance, nonbelted occupants were more likely than belted occupants to be covered by Medicaid (10.5% versus 1.4%) or to be uninsured (19.6% versus 5.6%). Mean hospital costs were 3.6 times higher for nonbelted than for belted persons ($2660 versus $738), and median hospital costs were 35% higher ($182 versus $135 {p=0.001}).

Observed and expected lifetime direct and indirect costs of injury were based on estimates for injuries resulting from motor-vehicle crashes using the human capital approach (6). Initial hospital costs, including professional fees, accounted for an estimated 30% of all lifetime direct costs; lifetime indirect costs were approximately three times greater than lifetime direct costs (5). The estimated savings in the lifetime cost of injury (direct plus indirect cost) associated with increased safety-belt use for the study population was more than $7.9 million. Based on these findings, the statewide savings in the long-term direct and indirect costs of injuries resulting from the increase in safety-belt use for 1 year were approximately $69 million. Reported by: TD Peterson, Iowa Methodist Medical Center, Des Moines. Div of Unintentional Injuries, National Center for Injury Prevention and Control, CDC.

Editorial Note

Editorial Note: Motor-vehicle crashes are the leading cause of death for persons in all age groups from 1 through 34 years. The proper use of lap and shoulder belts reduces the risk for death from motor-vehicle crashes by 43% and of serious injury by 43%-52%, making safety-belt use potentially the single most effective method for preventing injuries from motor-vehicle crashes (7). In addition to confirming that safety-belt use decreases the severity of motor-vehicle injuries (3), the findings in this report document that wearing safety belts substantially decreases the costs associated with motor-vehicle injury (8).

In the United States and in other countries, safety-belt use laws have been the most effective intervention to increase safety-belt use (3). Safety belts have been required in cars marketed in the United States since 1966; in 1983, however, before any state had enacted a safety-belt use law, the prevalence of front-seat occupant use was 15% (3). As of September 1, 1993, 43 states and the District of Columbia had implemented safety-belt laws, and the national rate of safety-belt use has increased to 62% (1). Rates of use are higher in states that allow primary enforcement of safety-belt use laws than in those that allow only secondary enforcement (3).*

One of the national health objectives for the year 2000 (9) is to increase to at least 85% the use of occupant protection systems (i.e., safety belts, inflatable safety restraints, and child safety seats) (objective 9.12). Achievement of this objective is being assisted by a requirement that, beginning with the 1990 model year, passive-restraint systems be installed in all cars marketed in the United States. In addition, 10 states now allow primary enforcement of safety-belt use.

Nearly 30% of the first-year medical costs of hospitalized persons injured in motor-vehicle crashes in the United States is paid by federal, state, or local government sources such as Medicaid and Medicare (10). Estimates of cost savings and of fatality and injury reductions associated with safety-belt use and other preventive measures can assist legislators and voters in making informed decisions in mandating safety-belt use. After the Iowa Safety Restraint Assessment, repeal of Iowa's safety-belt use law was considered; however, findings from this study had a substantial impact on the state legislature's decision to retain the law.


  1. National Highway Traffic Safety Administration. Card announces record year for highway safety {News release}. Washington, DC: US Department of Transportation, December 1992.

  2. Blincoe LJ, Faigin BM. The economic cost of motor vehicle crashes, 1990. Washington, DC: US Department of Transportation, National Highway Traffic Safety Administration, 1992; report no. DOT-HS-807-876.

  3. Campbell BJ, Campbell FA. Injury reduction and belt use associated with occupant restraint laws. In: Graham JD, ed. Preventing automobile injury: new findings from evaluation research. Dover, Massachusetts: Auburn House, 1988:24-50.

  4. owa Department of Transportation. Observational safety belt usage survey. Des Moines: Iowa Department of Transportation, Office of Driver Services, 1988.

  5. Nelson DE, Peterson TD, Chorba TL, Devine OJ, Sacks JJ. Cost savings associated with increased safety belt use in Iowa, 1987- 1988. Accid Anal Prev 1993;25:521-8.

  6. Rice DP, MacKenzie EJ, Jones AS, et al. The cost of injury in the United States: a report to Congress. San Francisco: University of California, Institute of Health and Aging; Johns Hopkins University, Injury Prevention Center, 1989.

  7. Evans L. The effectiveness of safety belts in preventing fatalities. Accid Anal Prev 1986;18:229-41.

  8. Peterson TD. Trauma prevention from the use of seat belts. Iowa Med 1987;77:233-6.

  9. Public Health Service. Healthy people 2000: national health promotion and disease prevention objectives -- full report, with commentary. Washington, DC: US Department of Health and Human Services, Public Health Service, 1991; DHHS publication no. (PHS)91-50212.

  10. Harris JS. Source of payment for the medical cost of motor vehicle injuries in the United States, 1990. Washington, DC: US Department of Transportation, National Highway Traffic Safety Administration, 1992; report no. DOT-HS-807-800.

* Primary enforcement safety-belt use laws permit law enforcement officers to stop drivers for a safety-belt law violation alone. Secondary enforcement laws require that a person be stopped for a separate infraction before being cited for a safety-belt law violation.

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