Research
Declining road fatalities: Less driving not the only cause

Fewer Americans are dying on the nation's roads, not only because they are driving less but because the type of driving has changed, says a researcher at the U-M Transportation Research Institute.

A new article by Michael Sivak in the June issue of Injury Prevention suggests that a larger-than-expected drop in road fatalities is partly due to disproportional decreases in rural driving and leisure driving.

"Rural driving is more risky than urban driving primarily because of high speeds, but there is evidence that it has recently decreased more substantially than urban driving," says Sivak, research professor and head of UMTRI's Human Factors Division.

"Analogously, leisure driving is more risky than commuter driving because of higher speeds, greater involvement of alcohol and more nighttime driving, but we are more likely to reduce leisure driving, if needed, than commuter driving."

Using monthly data from the National Highway Transportation Safety Administration, Federal Highway Administration and Energy Information Administration, Sivak performed statistical analyses on distance driven, proportion of driving on rural roads and the average price of unleaded gasoline as a proxy for the proportion of leisure driving. His study covered the period from January 2007 to December 2008.

He found that distance driven, proportion of rural driving and the price of gasoline accounted for 81 percent of the variance in road fatalities.

"The general economic downturn has led to a greater reduction in rural driving than urban driving because people in rural areas tend to have less income to start with than those in urban areas," Sivak says. "On the other hand, the price of gasoline in particular has influenced leisure driving more than commuter driving."