In a fairly ridiculous post, Freakonomics bloggers argue that public transit in America can be often less efficient than driving.
Now, the description of their conclusions as I have put it, contains most of the information needed to understand the caveats, namely, that there are some pretty inefficient transit networks in the US. But the conclusion as Dubner and Morris wrote it, essentially suggests that public transit needs to be looked at skeptically because it often isn’t much better than driving a car. What they really mean to say, is that transit generally works well in dense areas where ridership can be fairly high, and in the US we often have public transit for other reasons (social justice issues, area equity, etc). That’s a fairly trivial conclusion, so instead they worded things rather dramatically.
Update: Silly me, I should have read Jerrett Walker’s rebuttal, and you should too. Looks like I nailed his primary point too.