CDC Study Shows Fewer Traffic Deaths in Urban Areas
A new study from the Centers for Disease Control (CDC) shows that motor vehicle accident deaths remain a leading cause of death from injuries in the United States, but are less likely in major cities than in rural areas. To assess patterns in motor vehicle crash death rates, the CDC used data from the National Vital Statistics System and the U.S. Census Bureau for 2009, representing the 50 most populous U.S. metropolitan statistical areas (MSAs), a list which includes Denver.
According to the study, in 2009, motor vehicle crashes were the leading cause of death for people between the ages of 15 and 24, who represent approximately 14% of the U.S. population and comprised 22% of the 34,485 people who died in crashes. “Well-known risk factors (e.g., inexperience, lack of seat belt use, driving with teen passengers, and alcohol-impaired driving) for teens and young adults likely contributed to the higher MVC [motor vehicle crash] death rates observed for this age group,” writes The CDC’s Morbidity and Mortality Weekly Report (MMWR).
The overall MVC death rate for all 50 MSAs combined was 8.2 per 100,000 residents, as compared with a national rate of 11.1, the report says. Among those 50 MSAs, death rates ranged from 4.4 to 17.8, and 37 of those (representing 74%) had rates lower than the overall national rate. The study shows that crash rates were generally higher in southern states, with the highest rates concentrated in the southeastern U.S. Residents of the MSAs accounted for only 40% of all MVC deaths, even though those residents represented 54% of the U.S. population in 2009.
Urban sprawl, which is a function of residential density, land use mix, presence (or absence) of town centers, and street accessibility (a measure of street density and interconnectedness), might, in part, explain these findings (4). Previous research has shown that sprawl is more common in the southern United States, and that MVC death rates are higher in sprawling metropolitan areas than in compact metropolitan areas (5,6). A growing body of literature examines urban development and its association with MVCs. For example, urban sprawl has been associated with greater driving exposure (i.e., number of miles driven) (4,6).
As Nika Soon-Shiong reports in the Los Angeles Times, the study says that graduated driver licensing programs and programs to prevent impaired driving help to reduce fatal car crashes among young drivers.
Graduated driver licensing (GDL) programs initially limit teens’ independent driving and gradually introduce them to more complex and higher-risk conditions as they gain more experience and move through successive stages (i.e., permit, intermediate/provisional license, and fully unrestricted license) (7). GDL is one evidence-based intervention that can reduce crashes among young drivers, with stronger programs exhibiting greater effect (8). For example, fatal crash rates are lower where GDL programs restrict young drivers from having any passengers than where programs permit one or more passengers (7).
Effective interventions to reduce alcohol-impaired driving (e.g., sobriety checkpoints and ignition interlock programs for drivers convicted of alcohol-impaired driving) benefit drivers of all ages, including young drivers who have disproportionately high rates of impaired driving and involvement in alcohol-related fatal MVCs (9,10).
The Los Angeles Times notes that the authors of the recent CDC report concede that their study has some limitations. For one thing, they calculated death rates based on data from the National Vital Statistics System, which kept track of where the drivers lived, rather than where the crashes occurred. In addition, some death statistics were not reported because of liability and confidentiality concerns. The study’s authors also wrote that to solidify their findings, they needed data on other risk factors associated with fatal crashes, such as the blood-alcohol concentration of drivers, seat belt use, and speed, which were not available.
In a comment below the Los Angeles Times article, “Skeptical Scalpel” writes:
Couldn’t the lower death rates in urban areas be explained by two factors? One, vehicle speeds are generally lower when traffic is heavier. Two, fewer people may drive in urban areas. This is particularly true in cities with good mass transit systems such as New York.