Lloyd has already taken issue with the Freakonomics team's contrarian leanings regarding "primitive food", and Brian has slammed them for pushing "some of the worst climate journalism this side of Sean Hannity." So it will be interesting to see what we TreeHuggers make of their recent blog post about mass transit's potentially negative impacts on the environment. (This was regurgitated as a piece on Marketplace's Freakonomics Radio entitled Save the Earth, Drive Your Car.)
Essentially, the central tenet is this—mass transit only helps the environment if there are sufficient riders, and increasing ridership by adding more mass transit services may do more harm than good:
It is not clear that moving around large and largely empty vehicles is much of an improvement over moving around smaller ones. In fact, it may be worse. According to the Department of Energy’s Transportation Energy Data Book, in 2010 transporting each passenger one mile by car required 3447 BTUs of energy. Transporting each passenger a mile by bus required 4118 BTUs, surprisingly making bus transit less green by this metric. Rail transit admittedly fares better, at 2520 BTUs per passenger mile, but even this is not the kind of slam-dunk advantage over the auto that transit advocates might hope for.
Author Eric A. Morris goes on to note that the emissions involved with land use and vehicle manufacture are harder to equate, and play in transit's favor. He also notes that much of the low hanging fruit has already been picked in terms of areas where land use and population density are congruent with higher transit use. Here, he says, we should focus on increasing ridership through a combination of disincentives for car use and incentives for transit use. But in areas where population density and land use make transit less viable, he suggests we may actually save emissions by cutting transit services.
This isn't actually all that radical in many ways. It's pretty obvious that a mostly empty bus is going to pollute more than your average car. It's also obvious that encouraging ridership of existing infrastructure is going to have a bigger return on investment in terms of emissions saved than adding new infrastructure. But as is often the case with Freakonomics' observations (and any relatively short blog post for that matter), there are some important omissions.
Firstly, transit is not just about reducing emmissions—there are also significant social justice and quality of life issues to be considered given that being carless in America is like second class citizenship. Secondly, there is no telling what future energy prices will do for transit ridership, or on the otherhand whether the increasing electrification of private cars will offset the potential environmental benefits of transit and make the concept obsolete.
Either way, the post is a useful reminder that like most things "green", mass transit is no panacea to our environmental ills and must be considered as just one tool in our toolbox, alongside better planning, more efficient vehicles, telecommuting, car pooling and (gasp!) perhaps even putting quality of life before economic growth.