One strategy to reduce both building energy use and transportation energy use is smart growth — higher density development centered around mass transit nodes. In smaller dwelling units, especially if combined in apartment buildings, heating and electricity needs are lower. And it would seem likely that the location of units along transit lines will allow residents to reduce vehicular travel — especially if some of their commercial needs are combined in the development or provided by an existing town center.
However, it is unclear how much transit oriented development, as broadly construed in many state program contexts, reduces vehicle-miles-traveled (VMTs) per household. Within lower density suburban and exurban regions, residents drive long distances for multiple purposes and their VMTs are high regardless of whether they are in units located in “smart” locations. Typically, the transit service they are proximate too will meet only a subset of their needs.
The stronger factor which appears to control VMTs, at least in Eastern Massachusetts, is regional density. The closer one resides to the metropolitan core the more likely one can find what one needs close by. Infill developments which expand density within the core are the most efficient. Highly dense urban areas have GHG emissions per capita several fold below the national average — carbon emissions per capita in New York City less than one third of the national average. No one is suggesting that all future development should be in high rise buildings, but building on existing concentrations of development does seem to be the most effective approach from a climate change or fossil fuel reduction standpoint.
For a review of literature on this subject, see Growing Cooler. This publication makes a number of suggestions about state and local policies which would support growth in existing compact (more urban) areas. Many of these call for much stronger regional planning than we currently have today in Massachusetts and for a prioritization of climate goals above other goals in local aid allocations. So far, modest existing smart growth incentives have done little to channel growth to infill compact areas and, instead, have lightly sculpted suburban and exurban development. An interesting question is whether close in suburbs, in which growth would be relatively cool, can see their way towards allowing increased density by local decision-making.
Several related ideas, not mentioned explicitly in the Growing Cooler summary are: Land conservation in the exurbs, improvement of mass transit and bicycle/pedestrian options in the cities and the general challenge of subsidizing housing affordability in urban areas. Also needing further discussion is the problem of congestion (of traffic and housing) which generates opposition to increased density. In the Massachusetts context, the insights here suggest that we might want to channel 40B development to closer-in suburbs (including my own community) rather than remote suburbs. At the same time, it suggests that we need to work hard to preserve open-space, community paths and other amenities in close-in suburbs, so as to make density tolerable. More generally, every policy (from public safety to public education that operates to make urban living more attractive could be deemed a smart growth policy. Revitalizing the smaller urban areas in Massachusetts may make particular sense — the “gateway cities” strategy.
See also: Friends of the Earth Moving Cooler Summit — links at this location are to powerpoints from that conference. The talks by Winkelman and Anderson are especially useful — quantifying the potential impact of an aggressive policy favoring compact development.
Additional Notes, March 2009: These ideas were discussed at a recent informal seminar at the Lincoln Institute for Land Policy in Cambridge. The focus of the seminar was on the relative value of channeling development into close metro suburbs vs. doing “smart” development near transit hubs or existing exurban and rural centers. The discussion included the following points:
Inner suburbs travel much less than outer suburbs according to data from the RMV analyzed by MassGIS [basically, the reproduction in MA of the Growing Cooler literature]
- 40% of VMT is in long trips [this argues for more responsible vacation travel and may contribute to the income correlation with VMT and suggests that the residue of the observed MassGIS variation is even more powerfully influenced by density]
- Work travel as a percentage of total VMT has trended down and may be near 25% now [this tends to argue for the value of density in general over transit orientation because transit orientation mostly supports commuting].
- Is it possible to “nucleate” some employment growth in areas where there is housing but little employment; longest trips to work are to the central cities [works politically, supports desired development in exurbs, but should do less for VMT then concentration, given preceding observation]
- If an urbanization strategy is strongly pursued it could impoverish suburbs [a remote risk]
- Would be helpful to check MassGIS data on a percapita basis as well as per household [true shouldn’t change things much
- Not just a little increase in density will help — need to have all the pieces present to help [yes, this argues for developing in the denser metro centers and gateways that already have the pieces together rather than trying to scaffold development in improbable areas]