Can public transport “solve” the obesity epidemic?

My entry in Ted Baillieu's (proposed) competition. Flinders St Station - originally planned Swanston St elevation

A new US study has found that there is a significant association between public transport use and reductions in Body Mass Index over time.

This study has excited a lot of attention because it used a before-and-after “natural experiment” (see here, here, and here).

The researchers did an initial “before” telephone survey of residents living within one mile of a proposed new light rail line in Charlotte NC. They followed up with an “after” telephone survey 6-8 months after the new line opened.

There are some major methodological limitations with the study. Respondents self-reported their weight. The initial sample of 839 fell to 498 respondents in the follow-up phase. Only 26 respondents used the new line to commute on a daily basis.

Nevertheless, I have no difficulty with the proposition that those who choose to commute by transit are likely to be thinner than those who choose to drive to work. After all, transit requires the expenditure of more calories on walking and standing than driving does.

But in my view, the key issue is to what extent better health outcomes – and in this context specifically weight reduction – should shape transport policy. In order to look at that issue it is essential to understand what’s driving the “obesity epidemic” in Australia. Read the rest of this entry »