Does Urban Form Really Matter?
Does Urban Form Really Matter? This is the subtitle of a paper by Echenique et al., just published in the Journal of the American Planning Association.
The paper scrutinizes the claim that compaction makes cities more sustainable. Starting point is the finding of the US Commission of Integrated Transport (2009) that compaction has a modest effect in reducing vehicle travel. Echenique et al. posit that the social and economic costs needs to be treated comprehensively. Using modifications of the advanced transport-land-use model software MEPLAN, the authors model the impact of three different land-use developments in three English regions/cities, identifying 26 sustainability indices. The three developments are labeled dispersal, planned expansion, and compaction. Compaction reduces CO2-emissions from buildings and transport only between 1-5% compared with the dispersal scenario running from 1997 to 2031. Moreover, the differences in land-use due to spatial configurations are small compared to the impact of socio-economic change and population growth.
A little surprising is the relatively high increase in transport energy use of 10-38% from 1997 to 2031 in the baseline scenario (the other scenarios are only marginally different). With EU regulation, CO2-intensity of new cars will be reduced in average from >180gCO2/km in 2005 to 130gCO2/km in 2015 and (planned) 95gCO2/km in 2020. This massive reduction is mostly achieved by energy efficiency measures and is sufficient to reduce transport energy use even with increasing population and growth (assuming a car turnover time of 15 years). It would be interesting to see the underlying assumptions in the scenarios of this paper. (The background report at www.suburbansolutions.ac.uk speaks about “slightly more fuel efficient vehicles” without specifying details). However, irrespective of technological advances in vehicle fleet, the conclusions on compaction relative to the other scenarios remain valid.
Most interesting then is the net economic benefit. Also here, trend dominates the overall results: In baseline, economic costs of land use are high, as land prices and congestion increases, reducing economic competitiveness and costs for residents. Spatial developments make hardly a dent in this calculation and with different sign depending on the circumstances (compaction is suggested to be economically beneficial for the Cambridge region but economically disadvantageous for the other English areas studied). This aspect deserves more exploration. One can include various aspects into such cost calculation. For examples, one could include the time and convenience savings in non-motorized transport. Or one could develop a scenario where the increased monopoly land rents are taxed and other more economically harmful taxes on labor and capital are decreased. Such assumption would considerably change the results.
This consideration aside, the paper powerfully demonstrates that urban form policies have rather moderate and context-depending effects for reducing CO2-emissions. Compaction is no silver bullet. In turn, research focus should increasingly focus on sets of integrated policies, combining urban planning, transport demand management and infrastructure investment, identifying possible synergies and opportunities.
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