On its face, Vehicle Miles Traveled, or VMT, is a very simple metric: one car (or bus, or motorcycle) traveling one mile on a public road. To transportation experts, however, it’s precisely because the VMT implies so much more that it has become so useful.
The graph of VMT growth over the last century shows a near-ceaseless increase, punctuated only by blips marking wars or recessions. It tells not just the story of America’s increasing economic prosperity and standards of living, but also one in which those advances became increasingly intertwined with our reliance on the automobile.
Except, that is, if you’re Oregon.
Obligatory “Portlandia” jokes aside, the Beaver State has achieved something remarkable with its driving habits over the last decade and a half.
That’s not VMT per capita—a measure that has declined in many states, as Wonkblog’s Emily Badger recently noted.
No, it’s VMT total. Oregon wasn’t the only state that saw a drop—Michigan, Pennsylvania, and Rhode Island VMT declined too. But Oregon was exceptional for one big reason: it happened despite a rapid increase in both the state’s economic productivity and its population.
Driving Less, with More People
First, let’s review the facts. Between 1999 and 2013, Oregon added 600,000 residents, a growth rate above the national average. Its increase in GDP, meanwhile, was the greatest of any state that didn’t strike oil. Nor did Oregonians stop buying cars—vehicle registrations increased 17 percent according to the federal Office of Highway Policy Information, again slightly above the national average.
Yet despite all this, Oregon drivers drove 974 million fewer miles in 2013 than in 1999. The chart below, in which the axes intersect at the national average of VMT and GDP growth since 1999, shows just how anomalous Oregon’s case is.
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The difficulty of this accomplishment can’t be overstated. For years, the link between VMT, economic growth, and population growth was more or less taken for granted. In 2009, a study commissioned by the Cascade Policy Institute, a libertarian (and, notably, Oregon-based) think tank, concluded that “the connection between VMT and economic activity appears . . . intimate and potent.”
Oregon’s ability to break this mold is critical, for it shows that economic prosperity and population growth need not mandate increased driving and all the problems it can bring.
Planning for the Future
So what’s causing Oregon’s drop in VMT?
First, the state’s population is more urban now than it was in 1999. Over the past fifteen years, about half of Oregon’s growth was concentrated in Clackamas, Multnomah, and Washington counties, which form the core of Greater Portland. Meanwhile, the empty parts of the state are getting emptier: seven of the state’s nine most sparsely populated counties declined in population in the same span of time. In a 2013 blog post, the state Office of Economic Analysis confirmed that a drop in rural driving was the main cause of the state’s overall VMT decline.
This phenomenon isn’t unique to Oregon—other high-growth states, like Georgia and Texas, are also seeing diminished rural populations. By and large, though, Oregon has proven unique in its ability to prevent the sprawl of jobs and homes that usually accompanies such metropolitan growth and leads to more VMT.
This probably didn’t happen by accident. On the contrary, Oregon is famous among planners for its stringent land-use policy. In 1973, state lawmakers passed SB 100, which organized a Land Conservation and Development Commission (LCDC) tasked with creating statewide land-use goals. The bill came on the heels of a well-known speech from Gov. Tom McCall to the state legislature, in which he decried the proliferation of “sagebrush subdivisions, coastal ‘condomania,’ and the ravenous rampage of suburbia.”
The LCDC’s mandate is comprehensive, but its most lasting contribution may be the requirement that Oregon cities create Urban Growth Boundaries. The boundaries must contain a 20-year supply of land to meet projected population and employment growth, but cannot be expanded unless “needs cannot reasonably be accommodated on land already inside.”
This strict policy has never been totally free of controversy. Conservatives, for one, have long claimed that it artificially inflates housing prices, though evidence of this is hazy at best. But it’s important to note that the boundaries don’t generally constrain how much can be built, just where people can build.
Statistics from Greater Portland, which comprises half of the state’s population, provide the best evidence of this success. From 2005 to 2013, the Portland area added about as many new housing units per new resident as Dallas and Houston, and more than Atlanta, Denver, or Seattle, according to American Community Survey statistics.
Meanwhile, data on commuting habits shows evidence that people in Portland, on average, don’t have to travel as far to work as other Americans.
For starters, a larger proportion of Portlanders work from home than in any other major city (in a tie with Austin, Texas). And overall, compared to similarly sized urban areas, the Portland region has both a fairly small percentage of commutes over 50 miles and a large percentage of commutes under ten miles. While the latter measure declined slightly in recent years, it did so less than in those other cities, another indication that Portland has more limited sprawl than the Orlandos and San Antonios of the country.
What’s more, Portland commutes don’t divide along socioeconomic lines as much as in other cities. The difference between the percentage of lower-income workers with short commutes and higher-income workers with short commutes is less than a percentage point, compared to seven points in the Las Vegas area and almost ten in Cleveland.
This, in turn, makes it easier to build political support in Portland for investments in non-automobile transportation infrastructure geared toward shorter-distance commuters, including mass transit and bike lanes, since the benefits are better distributed across social classes than in other cities.
Ironically, the one downside to Oregon’s VMT decline may be the state’s finances. In an attempt to address the declining value of the state gas tax, Oregon is launching a pilot program that will charge drivers based on miles traveled rather than gasoline consumed. In light of the statewide VMT trend, however, it’s safe to say that such a policy would benefit almost any other state more than it will Oregon.
Taxes aside, though, it’s clear Oregon has found a way to grow that doesn’t necessarily mean driving more. And if the rest of the country can learn from its example, the U.S. could be well on its way to crafting a more sustainable, equitable, and efficient national transportation policy.