I've spent the last several days at the Intelligent Transportation Society of America's 20th annual conference in Houston, and today I was on a panel on transportation and climate change with Deron Lovaas (Natural Resources Defense Council), Reid Ewing (University of Maryland), Wendell Cox (demographia.com) and Dick Mudge (Delcan Corp).
The U.S. Department of Transportation has made environmental sustainability one of its key strategic planning goals, and much of the talk was on reducing vehicle miles traveled, or VMT. But is this an appropriate metric? I don't think so.
The first slide in my powerpoint noted that climate change policy was really about reducing greenhouse gases, the most prominent of which is carbon dioxide. This has nothing to do (directly) with travel. It's not a big leap, for example, to think of someone conducting most of his or her travel in an electric car powered by hydroelectric or nuclear power, two carbon-free sources of energy.
The solution to climate change, interpreted as reducing greenhouse gases, is to stop burning fossil fuels. Burning fossil fuels, mainly oil and coal, generate carbon dioxide. So, its not the travel that is the problem; it's the fuel we use to generate the energy needed to propel a vehicle from point A to point B. Thus, VMT is a very poor metric for evaluating progress toward climate goals.
The focus on VMT as a climate change strategy is actually quite telling. VMT reduction is a planning metric, not a climate change metric. VMT reduction is really just another way of attacking urban sprawl and low density housing.
That won't help reduce carbon dioxide production, however. The only solution to that is to stop using fossil fuels. That, in the end, requires a technical solution, not necessarily (or even primarily) behavioral change.