Increased rural vehicular mortality rates: roadways with higher speed limits or excessive vehicular speed?

The purpose of this study was to assess whether higher roadway speed limits and excessive vehicular speed were contributing factors to increased rural vehicular mortality rates in the State of Alabama.

During a 2-year period from January 2001 through December 2002, data were collected from Alabama police crash reports and EMS patient care reports. Police crash reports and EMS patient care reports were linked utilizing an imputational methodology. Vehicular speeds were estimated speeds extracted from police crash reports. Vehicular speeding was defined as estimated speeds greater than posted speed limits.

A total of 38,117 reports were linked. Of those, 30,260 (79%) and 7,857 (21%) were injured in rural and urban settings, respectively. The frequency of vehicular speeding was significantly higher in rural (18.8%) than in urban settings (9.4%) (p < 0.0001). At vehicular speeds less than 26 mph, mortality rates for occupants of speeding and nonspeeding vehicles were not significantly different in rural (1.68%, 0.82%) and urban (1.44%, 0.59%) settings (p = 0.78,1.0), respectively. On roads with posted speeds of 26 to 50 mph, mortality rates for occupants in speeding vehicles were not significantly different in rural (3.75%) and urban (2.23%) settings (p = 0.1360). For occupants of nonspeeding vehicles on roads with posted speeds of 26 to 50 mph, mortality rates were significantly greater in rural (0.72%) than in urban (0.35%) settings (p < 0.0032). On roads with posted speeds of 51 to 70 mph, mortality rates for occupants in speeding vehicles were not significantly different in rural (5.80%) and urban (4.95%) settings (p = 1.0). For occupants of nonspeeding vehicles on roads with posted speeds of 51 to 70 mph, mortality rates were significantly greater in rural (1.92%) than in urban (0.94%) settings (p = 0.01).

Vehicular speeding occurs with significantly higher frequency in rural settings. This imparts a greater overall vehicular mortality rate. At higher rates of speed, mortality rates for travel above the posted speed limit are similar in rural and urban settings; however, mortality rates for travel within the posted speed limit are greater in rural settings. This suggests factors beyond higher and excessive vehicular speed impart higher rates in rural settings.