A couple of weeks back I reviewed the 2011 Urban Mobility Report (see post), finding  credence in its measures of traffic congestion but seeing little value in its public policy solutions. My criticism were mild compared to the scathing critique by Todd Litman, head of the Victoria Transportation Policy Institute, who found the study worse than useless. You can read his withering attack here.

One argument that intrigued me was his contention that congestion has not been intensifying over the past several years, as the Urban Mobility report suggests. If anything, people are driving less and congestion is easing. Writes Litman: “U.S. vehicle travel peaked in 2003, and contrary to the UMR’s assumptions, there is no evidence that total vehicle travel will grow significantly in the future, due to demographic and economic trends that are reducing per capita vehicle travel in the U.S. and other developed countries.”

In a recent report, “The Future Isn’t What It Used to Be,” Litman shows how key trends that drove the increase in Vehicle Miles Driven are leveling off. Look at the chart at the top of this post, which shows the growth in U.S. vehicle ownership. The numbers started leveling off before the 2007 recession. That’s because among affluent and middle-class Americans, nearly every person with a driver’s license now has his or her own car. A steady increase in the number of drivers had propelled Vehicle Miles Traveled for decades. Now that everyone has a car, that impetus has lost its momentum. (There may be a pent-up demand for automobiles among lower-income Americans but tighter credit conditions and wage stagnation makes it difficult for them to join the ranks of auto owners.)

Further, Litman points out that as aging Baby Boomers reach retirement, they will drive less. Factor in the end of cheap fuel prices, a residential real estate crash that hit hardest in exurbia where people drive greater distances, the continued migration to metro areas from rural counties where people also tend to drive longer distances, the increasing disinclination of young people to buy cars, the rise of telework and a number of other reasons, it’s no wonder that Americans are driving less. Indeed, about the only major factor pushing VMT numbers up is a growing population.

Of course composite numbers at the national level can obscure a lot of cross-cutting trends. The decline in VMT has been less pronounced in Virginia, not surprising given the faster-than-average population growth and stronger-than-average economy here.  Even so, after peaking in 2008, VMT dipped in 2009 and 2010. It would be really interesting to view the numbers by transportation district or, even better, by metropolitan area. I would expect to see that VMT remained strong in Northern Virginia but that the Rest of Virginia tracked the rest of the country. If that conjecture is correct, it would call into question the need to sustain a large road/highway construction program anywhere outside Northern Virginia. And even in NoVa, one could argue,  new construction there would best be channeled into projects like retrofitting Tysons Corner transportation system than blazing new paths through undeveloped countryside.

At the very least Litman’s argument calls into question the extrapolation of past trends indefinitely into the future. The public policy apparatus of Virginia is operating on the premise that VMT will continue growing at historical rates. But if that premise is unfounded, so may be the justification for many of the transportation projects on the books.