Peak Car Travel in the United States: Two-Decade-Long Phenomenon at the State Level

Peak car travel is an international phenomenon that became evident in the United States on a national scale in 2004. Potentially related to peak car travel is the decoupling of economic growth from driving levels. A wealth of research has addressed these phenomena on a national scale in the United States and other developed countries. Yet few studies have been undertaken on other geographic scales, especially the statewide scale in the United States. This study investigated U.S. state-level driving and economic patterns from 1980 to 2011 to understand occurring changes. The research results showed that peak car travel first occurred at the state level as early as 1992 in Washington State, whereas another 10 states peaked in 2000. By 2011, 48 of the 50 states had peaked. The longevity of this phenomenon at the state level provided evidence that peak car travel in the United States was a more permanent phenomenon than previously thought. In addition, the decoupling of economic growth from driving was evident at the state level. In the 1980s, these indicators were positively correlated at the state level. A significant change occurred by the 2000s, however, when any significant connection ceased for most states. For four of the earliest peak car travel states, the relationship between economic growth and driving turned negative. This finding showed that decreases in driving were not associated with negative economic consequences. Rather, in several states, driving reductions were now associated with increased, rather than decreased, economic growth.