Car crash death rates get increasingly high as population density drops, fueled in part by lower seat belt use in the remotest rural areas, a US study suggests.

“We already knew that death rates were higher and seat belt use was lower in rural versus urban areas,” said lead study author Laurie Beck, of the US Centers for Disease Control and Prevention (CDC) in Atlanta.

“This study expanded those findings to show that, even within rural areas, there are differences in passenger-vehicle occupant death rates and seat belt use,” Beck said by e-mail.

Car crashes are a leading cause of death nationwide, CDC researchers note in the Morbidity and Mortality Weekly Report, online September 22. While collisions are more common on urban roads, fatalities occur more often in rural regions.

For the study, CDC researchers examined data based on six categories of population density from the most metropolitan, with at least 1 million city residents, to the most rural, with fewer than 2,500 residents living in urban communities.

Passenger vehicles included cars, light trucks, vans and sport utility vehicles. Crash deaths focused on adults 18 or older, and excluded younger passengers.

Seat belt use ranged from about 89% in the most urban counties to slightly less than 75% in the most urban counties.

Lower seat belt use in rural areas clearly contributes to higher death rates

One limitation of the study is that researchers calculated crash-death rates based on where the victim lived, not where the collision occurred, the authors note. This might have underestimated the difference in fatalities between urban and rural areas because drivers who travel across different regions are more likely to head from small towns to big cities, the authors point out.

Still, lower seat belt use in rural areas clearly contributes to higher death rates, said Jacob Sunshine, a researcher at the University of Washington in Seattle who wasn’t involved in the study.

“Other potential contributing factors include higher speeds that are readily achieved in rural areas compared to urban areas; increased per-capita levels of impaired driving; and less proximity to designated trauma centres following traumatic injuries sustained in a motor vehicle crash,” Sunshine said by e-mail.

Lower wages and higher unemployment in some rural communities might also mean more people are driving older cars with fewer safety features to prevent fatalities in a crash, Sunshine added.

But the study also shows that stricter seat belt laws can make a difference, especially with more stringent enforcement, he said.

“Seat belts are proven to save lives and we should educate drivers and passengers about their benefits,” Sunshine said. “Laws are important too; enforcement needs to be a priority, particularly in rural areas.”