Ken Anderson, of Blacksburg, has forwarded to me a 2003 study, “Highways and Sprawl in North Carolina,” by David T. Hartgen, professor of transportation studies at the University of North Carolina-Charlotte and written for the John Locke Foundation. Clearly, the Tarheels are asking many of the same questions that we are in Virginia.
For this study, Hartgen surveyed a voluminous amount of academic literature on the connection between transportation and “sprawl,” and compiled a massive amount of data: population change by census tract, household size, job creation, income growth, travel times, and road projects constructed during the 1990s. His major conclusion: “This study between growth and road improvements in North Carolina finds only a modest correlation between road investments and [residential] growth.”
“Major road improvements can have a modest effect on the magnitude of growth and its specific location,” Hartgen writes, “but they are not in and of themselves either sufficient or necessary for growth. Most growth will occur in the absence of road improvements, going to areas where space is available.”
Rural economic development. The backdrop of Hartgen’s study was a program by North Carolina to jump-start growth in small towns and poor counties to bring 90 percent of the state’s population within 10 miles of a four-lane road, an effort projected to cost about $13 billion back in 1989. (You can double that number to get an idea of what it would cost today.)
“The determinants of [census] tract growth are largely local,” Hartgen concluded. “Tract growth is influenced largely by local economic health, housing quality, schools, taxes, infrastructure provision and a host of other factors. This means that local governments hoping to spur growth should generally look within, not to Raleigh or Washington, for the key actions needed.”
That finding should give pause to communities in Southside and Southwest Virginia that look to multibillion-dollar road improvement projects — the Coalfield Expressway, Interstate 73, four-laning of U.S. 58 — for their economic salvation. The projects are so vast in scope that they are, for all practical purposes, unaffordable. Even if the state, local and federal government could scrape up the billions of dollars required, the investment would yield low economic returns. It would make far more sense — this is Bacon speaking, not Hartgen — to invest the money otherwise: in education, in broadband connectivity, in quality-of-life enhancements.
Induced demand. Hartgen also takes a position contrary to one that I have espoused on the issue of “induced demand.” By temporarily lowering the cost of travel, many have argued, road improvements encourage families to move farther from job centers to areas where they can find more affordable housing. Over time, as new development projects arise on the urban periphery, those roads fill up. The result: More people driving farther — on roads that become increasingly congested.
Hartgen found that the phenomenon of induced demand does exist, but it is relatively minor in explaining where growth occurs. “These effects are likely to be largest in suburban tracts where growth is rapid and where congestion increases the area’s attractiveness. However, the relative impact of these effects is modest, about 2-14 percentage points added to baseline growth. And the overall effect is typically small. An additional 500 persons (a large effect of a road improvement) would generate about the same traffic as a single small McDonalds Restaurant, about 1,500 trips per day.”
However, I think there is one big hole in Hartgen’s methodology. Induced demand does not occur overnight. It takes years for developers to assemble the land, line up the permitting and build new housing tracts, and even longer for new households to move in. In other words, there is a built-in delay. However, the scope of Hartgen’s project covers the decade of 1990 to 2000. As he notes, “This study does not look at the longer-term (20-30 year) impact of major roads on recent growth. Such a study while useful is beyond the scope of the research and introduces even greater uncertainty as to the causes of growth.”
More accurately stated, then, Hartgen finds that the induced demand of road projects is modest within a time frame of 10 years or less. Beyond that — who knows?
Density caps. Hartgen makes one other interesting point: The location of growth is guided less by the existence of roads than by the amount of room to accommodate it. “When local planners set zoning, they are essentially specifying its residential capacity. Growth slows as it nears this limit, because land prices rise and parcels get harder to assemble. Developers sometimes receive variances to increase development above current zoning limits but they also look to nearby less-developed tracts. Near urban regions this growth goes primarily to the edges of urban regions where tracts have room for it.”
Extrapolated to Virginia, that means, if the residents of Loudoun, Prince William, Clark, Fauquier, Culpeper, Orange and other counties on the edge of Northern Virginia want to preserve their small-town and farming way of life, stalling transportation improvements won’t do the job. As long as core jurisdictions — Fairfax, Arlington and Alexandria cap residential density while creating new jobs, the development will move outward, roads or no roads.
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