Although conventional wisdom and crowded streets might suggest otherwise, vehicle ownership, fuel consumption, and miles driven per year seem to be on the decline.

These three indicators, referred to cumulatively as “motorization,” have been studied extensively by Michael Sivak, a research professor at University of Michigan’s Transportation Research Institute, in his six part research study “Has Motorization in the U.S. Peaked?”

Sivak just released the most recent installment of his study which focuses on the relationship between road transportation and economic activity, and his findings suggest that the decrease in motorization is not caused by economic factors.

In his previous reports, Sivak studied changes in the number of registered light-duty vehicles and related changes in the number of miles driven and the amount of fuel consumed. Sivak’s research indicated that despite population growth, all three indicators of motorization reached their height around 2004 and have been declining ever since. Because the decline of these rates began before the Great Recession of 2008, Sivak argued that their decline was not likely caused by the economic factors.

Sivak’s most recent report examined the relationship between distance driven and inflation-adjusted GDP, as well as fuel consumed and inflation-adjusted GDP. The results of his research showed that distance driven per GDP reached its height in the 1970s and plateaued until the early 1990s, when it began to decrease. By 2012, distance driven per GDP had experienced a 22 percent decrease from its highest point, which occurred in 1977.

The amount of fuel consumed per GDP also reached its height in the 1970s, and experienced a 47 percent decrease by 2012. According to Sivak, the dramatic decline in fuel consumed per GDP can likely be attributed to improved vehicle fuel economy over the years.

Sivak’s most recent findings support his assertion from earlier research that the reduction of motorization is caused by “fundamental, noneconomic changes in society.” But if economics aren’t the primary factor in motorization’s decline, what is? Sivak guesses that factors like increased telecommuting, increased use of public transportation, increased urbanization of the population, and changes in the age composition of drivers are likely contributors to motorization’s decline.

Abstract, UMTRI Publications