Several friends have sent me this fantastic report, produced as a collaborative effort by researchers at a couple of smart growth organizations and universities. It takes a long look at the role of the built environment in climate change, and it notes that, as I’ve said here before, simply improving efficiency or switching to alternative fuels will not do enough fast enough to solve our emission issues. We also need to improve the way that we build our cities.

There are plenty of points in there worth highlighting, but the factoids that grabbed my attention were that 1) vehicle miles traveled since 1980 have grown three times as fast the population and almost twice as fast as vehicle registrations, and 2) land is being consumed for development at a rate three times faster than population growth. In other words, we’re moving steadily farther out ever faster.

I took a look at some of the dynamics at work here, but a broader point is that it’s very difficult for local governments to improve their building strategies, for two reasons. First, roads and gasoline are far too cheap. The vast majority of roads in this country are free, meaning that drivers don’t have to pay the cost of the negative congestion externalities they impose on others, meaning that the level of driving his far higher than is socially optimal. Similarly, gas prices don’t include the negative externalities of carbon emissions, again leading to greater than optimal driving. Underpriced roads and gas mean that too few people use transit, and governments have to work harder to make smart growth oriented plans and transit competitive.

Secondly, even if governments are willing to take on the challenge of reining in outward growth, the federal government makes this incredibly difficult. Relative to transit, far more money is available for new roads with far fewer strings attached. If constituents are demanding transportation solutions, the easiest way to do something about it is to build more roads. Personally, I’m amazed that so many cities are embarking on plans to build new transit lines. It’s a testament to the severity of our congestion problems that this is the case.

I’m sure no one is surprised to hear that the structure of our build environment contributes significantly to carbon emissions and makes finding solutions to climate change more challenging. We shouldn’t assume that the negative, unintended consequences of sprawl end there. Several studies have shown how sprawl enables obesity. Others have shown how low-density settlement reduces productivity. I suspect our settlement patterns exacerbate inequality, by filtering struggling middle-class families into distant exurbs, where upward economic mobility is limited and expenditures on transportation outweigh savings on home prices.

It’s a bad situation, but we could begin to improve it immediately with just a few legislative tweaks. In light of our environmental difficulties, shifting a couple billion from new highway construction to transit construction and ongoing transit subsidies seems like a no brainer. So does a change to ease the rules for authorizing funding of transit projects. Maybe at some point, politicians will even be willing to entertain the idea of a carbon tax. The point is, we don’t have to grow like this; we don’t have to build sprawling subdivisions 60 or more miles from the nearest business center. It’s long past time to fix the policies that encourage us to sprawl.