Factors affecting the decline in VMT: A new SSTI report

By Chris McCahill
SSTI has released a paper outlining factors contributing to the recent decline in American driving and the implications for transportation planning. As previously reported, per capita VMT has decreased steadily for the past eight years, resulting in a slight decrease in overall VMT during that time period. In contrast to prior fluctuations, this recent dip in VMT does not appear to be driven by economic conditions or high gas prices. Instead, researchers attribute this new trend to a culmination of decades-long growth, along with changing personal preferences.
As researchers such as Steven Polzin suggested even before the recent downturn, many of the factors that contributed to rapid increases in driving during the twentieth century have nearly reached their peak. These include the rise of women in the workforce, the baby boom, an emerging middle class, and growing automobile ownership. As these trends flatten out or decrease, so too will VMT in the coming decades.
Another important consideration is that, while trip lengths and trip frequencies rose for decades, Americans appear to be pushing the upper bounds of how much they will drive. The costs of automobile ownership, the amount of time people are willing to spend in their cars, and rising levels of traffic congestion impose limits on the number of miles each person can realistically travel.
Finally, Americans have begun to favor a style of living in which driving plays a less important role. Young people, in particular, are driving less and relying more on transit, biking, and walking, regardless of employment status or income. Compact, mixed-use living arrangements are becoming more popular, particularly among young adults and aging retirees. These trends are generally expected to continue, driving down per capita VMT even further and limiting overall VMT growth.
Read and download the full paper by clicking here.
Chris McCahill is a Senior Associate at SSTI.