National highway investments and some regulations, such as the federal Corporate Average Fuel Economy standards, are closely linked to how much use our roads get. One vehicle traveling one mile equals one vehicle mile traveled (VMT), the benchmark statistic for vehicle and road usage. Every year, about three trillion VMT are recorded in the U.S. With support from Volpe, the Federal Highway Administration (FHWA) is offering new projections on what our miles traveled by vehicle might look like in 30 years.

While auto usage has historically paralleled economic growth, dipping and rising with recessions, current auto travel has yet to bounce back from the recession that began in the late 2000s. The model Volpe developed to produce new VMT projections shows that growth is likely to pick up slightly in coming years, but will remain well below its historical rate, aligning more closely with population growth over the next few decades.

Volpe’s History with VMT

“We started investigating VMT with approaches we might use to model and forecast VMT back in 2009,” said David Pace, an economic analyst at Volpe who helped conduct this research. “That was an initial literature review. We investigated the influences on VMT—the economic and demographic influences—and how other institutions, government agencies, and academia might be approaching the task of forecasting VMT. Then, around 2010, we started building a model to provide yearly VMT projections for FHWA.”

FHWA released its current VMT projections, prepared with support from Volpe in May 2014. Over the previous 30 years, VMT growth averaged more than 2 percent annually, but much slower growth is likely for the next 30 years: just 0.75 percent annual growth, according to Volpe’s projections. VMT trends and projections impact FHWA research and policies, and are also used in state pilot programs testing fees based on distance traveled.

Impacts from Lower VMT

Other than the lingering effect of the last recession, a variety of other reasons help explain why the rate of VMT growth has slowed. Car ownership appears to be nearing a saturation point and young adults are driving less. Debt from higher education may be holding young people back from making big-ticket purchases such as homes and automobiles. Gasoline prices have also become more volatile and remain relatively high by historical standards.

“With many of these aspects, there really isn’t a lot of robust, complete data yet, so it’s difficult to determine the exact influence each of these reasons is having,” Pace said. “A lot of the effects of the recession hit households at the lower end of the income bracket. When lower-income homes see a decline in income, the effect on driving tends to be fairly pronounced. People at higher income levels, by contrast, don’t see as much of a pronounced effect.”

Slower future growth in VMT is likely to have several effects. There will be slower revenue growth for the Highway Trust Fund, which supports highway construction, transit facilities, and other infrastructure improvements. While congestion levels in urban areas seem unlikely to decline, they are also unlikely to become much worse with slower future VMT growth except in a few isolated locations. There may also be environmental benefits from a slowing rate of growth in the number of miles traveled by vehicles.

There is still plenty of uncertainty about what will happen to VMT growth over the next 30 years. Truck use continues to grow and a return of widespread economic prosperity could reinvigorate automobile use. A stronger employment market and lower energy prices, for instance, would give households more disposable income to buy cars. The prospect for automated vehicles adds even more uncertainty to future growth in travel. One thing is certain: even if VMT growth continues to remain slow, the personal vehicle is unlikely to go away anytime soon—after all, more than 85 percent of Americans get to work by car, either alone or via carpool, and similarly large fractions of trips for many other purposes, such as shopping or personal business, are also made by car.