this post was pirated from the Freakonomics blog:

*this is by the main author of Freakonomics and made me laugh out loud:
(original post here)

May 1, 2008, 9:36 am

More Analysis of the Environmental Impact of Walking vs. Driving

By Steven D. Levitt

Last month I blogged about Chris Goodall’s claim that walking could exacerbate global warming more than driving if the person doing the walking gets his or her calories from foods like beef or milk.

A group called the Pacific Institute has done some further analysis of the data. Their analysis suggests that for most reasonable assumptions about the diet of the walker, driving generates a greater carbon footprint.

I like how the Pacific Institute approached this issue. They used data and clearly articulated assumptions to better understand these claims. They put everything out on the internet so that people can check what they have done and challenge it if appropriate.