Sometimes you find things in the darnedest places. While reading Randal O’Toole’s testimony on Washington’s Growth Management Act (spoiler: he’s opposed), I see he references work by David Brownstone down at UC Irvine:
As University of California (Irvine) economist David Brownstone concluded after thoroughly studying this issue, the link between land uses and driving is ‘too small to be useful’ in attempting to save energy or reduce emissions.
Hmm, as someone they tell me was a Great Communicator used to say: trust, but verify. So let’s see what Brownstone has to say in his most recent paper:
The estimation results indicate that residential density has a statistically significant but economically modest influence on vehicle usage, which is similar to that in previous studies. However, the joint effect of the contextual density measure (density in the context of its surrounding area) and residential density on vehicle usage is quantitatively larger than the sole effect of residential density. Moving a household from a suburban to an urban area reduces household annual mileage by 18%.
I’ll leave you to speculate as to why O’Toole would cite authoritative sounding sources that, on closer review, clearly do not say what he would like you to think.
Nevertheless, the result of the Brownstone paper is very important: density on the census block level has a relatively small impact on vehicle miles traveled (VMT). Regional effects dominate. In other words, density is much more important on the regional scale than the local scale. If you want to decrease VMT, you need to increase regional density, not just build TOD projects at transit stations.
This study lends support to things we’ve explored from an intuitive perspective before (and data is almost always better than intuition). It explains how places like LA and Orange County can show up in lists of lowest household gasoline use* – even if you have to drive, you never have to drive very far. And it also shows a possible way forward for a region that shows up on lists of highest household gasoline use – the IE. Rather than focus on building TOD projects near transit stations, officials in the IE should upzone everywhere. They should allow things like Palms-style apartments and redevelopment of Cudahy-style lots the way they’ve been redeveloped in their namesake city. Because while the IE will probably never be able to emulate New York City’s travel patterns, it could certainly emulate LA’s.
*Note: 7 of the 10 worst gas guzzling cities are in the South (excluding Texas), which also makes sense in the context of my post on suburb types.