LA Land Use Patterns Help Reduce VMT

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.

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7 thoughts on “LA Land Use Patterns Help Reduce VMT

  1. dan

    Back in 2008, Chris Bradford at his Austin Contrarian blog (http://austinzoning.typepad.com/austincontrarian/2008/09/the-association-between-density-and-mode-of-commuting.html) posted some basic correlation charts on transit and various ways of calculating density. What he found was that the greatest correlation for high transit use was what he called a “clump index” (the weighted density divided by the standard density), which generally tells you how much density is focused, rather than evenly spread.

    In fact, cities with relatively low densities but high “clumping” (probably often along transit corridors) experience high transit use. Admittedly, this isn’t super scientific research, but this has always seemed intuitive to me:

    — If your city is focused along fixed transit routes, you can experience full(er) access to what the metropolis has to offer through transit. This, coupled with the competitive low cost of transit may persuade you against the costs of owning a car, or against driving your car everywhere you go.

    — If destinations and origins are spread evenly, then owning a car and using it often makes much more sense in order to have a comparable share of access to the metropolis.

    In other words, I intuit (generally) that it’s not “high” density along transit routes that boosts transit ridership, but rather “higher” density than non-transit-accessible areas.

    Reply
    1. letsgola Post author

      Thanks for the link; it’s a good post. Note that the Brownstone study relates to VMT, but not mode share (though there is a dummy variable in his model for rail transit). The Austin Contrarian post would suggest that though LA’s land use pattern results in relatively low gasoline use, it will not lend itself to higher transit mode share.

      The issue I’d take with that analysis is that it omits another important variable: clumping of jobs. All of the cities that have high weighted population density to standard population density ratios will also have a high degree of job clumping in the CBD (NYC is off the chart; “legacy” cities Boston, Phila, Chicago, DC, & SF are the rest). So residential clumping and job clumping are pretty codependent.

      So the question would be, which variable drives higher mode share? Job clumping or residential clumping, or some combination? The question is important, because if job clumping dominates, then it wouldn’t matter if we reshape residential zoning to clump density around transit stations.

      The really interesting question for LA is if you can increase transit mode share in a city that is dense but not very clumped (in terms of both housing and employment). I’m not sure if there’s a good city to use as a comparison; LA might be pioneering this question & transformation the same way that LA defined the polycentric city. With 10 million people in LA County already living and working within the LA land use pattern, it’s unlikely that we’re going to remake the city to function like NYC or Boston.

      As you might guess from this blog’s tone, I’m optimistic that transit works in a place like LA.

      Reply
      1. Dan

        Thanks for the response. It would be great if we had reliable job location data from the census or otherwise — then we could run an analysis like Bradford’s that would likely be much more accurate. I would completely agree that job clustering is the second largest determinant of transit use (behind availability of parking..). Los Angeles will likely never have an economic engine that makes sense to be clustered into high-cost office building cbds.

        At the same time, I don’t think that it quite “doesn’t matter” that housing be located near transit. It definitely helps for housing to be within walking distance of a transit stop (no need for it to be directly on top). But if I had to choose (and had sim city powers) I would definitely put jobs on top of/adjacent to transit before I thought about housing.

        I’m also optimistic that transit works in a place like LA — though I tend to be more interested in comprehensive bus lanes than in skeletal rail line networks (but you need both!).

      2. letsgola Post author

        Totally agree on need for bus lanes in LA in addition to rail network! I’ve been meaning to post about bus service but just haven’t gotten to it yet…

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