This site uses cookies. By continuing to use this site you agree to our use of cookies. To find out more, see our Privacy and Cookies policy.
Skip to the content

IOP A community website from IOP Publishing

Powered by Movable Type 4.34-en

Sustain to gain: May 2012 Archives


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. 


Walking and cycling dominate urban transport in Asia and Africa. This statement is worth repeating. Walking and cycling dominate urban transport in Asia and Africa. It is one of the key statements in the book "Urban Transport in the Developing World", subtitled "A Handbook for Policy and Practice", edited by Harry Dimitriou and Ralph Gakenheimer. But it is much more than a handbook. It is the most comprehensive overview on the topic. With more than 600 pages, take your time reading it. While there is some redundancy, reading this book carefully will provide you with a superb, encompassing understanding of urban transport in the developing world.

Here is the book's story. 60% of the world's population live in Asia, and Asia is the epicenter of the global urbanization wave. Asia is also the focal point of incredible motorization with China alone being projected to have in 2050 nearly as many cars, as the world has currently on its roads, in totol: 700 million cars. An Asian city also gives its name to one of the key concepts I extracted from the book: the Bangkok syndrome. Similar to their OECD counterparts, Asian and African cities start with dense, walkable city cores. At the beginning of the last century, OECD cities invested in the then upcoming rail-based transport infrastructure, shaping cities profoundly. With the relatively slow but profound rise of automobility, American cities developed into low-density automobile cities, while European cities kept their inner cities served with public transit. Asian and African cities seem to be mostly on a different trajectory: They skip the stage of public transport infrastructures and move directly into individualized motorized mobility. This is too some degree quite surprising: Relative to their GDP, cities of the developing world invest much more into highways, citizens proportionally much more into personal transport than their OECD counterparts do and have done (see e.g. Jeffrey Kenworthy's contribution). Inversely, these developing cities have high population density and are unsuitable for car transport. As a result, especially Asian cities develop into 'motorcycle' cities (Barter, 2000): motorized two-wheelers are best adapt to navigate the traffic disasters, but are subject to high accident rates and still face congestion.

Distribution and accessibility is another, related theme that develops continously across chapters. As the introductary statement indicates, paraphrased from Setty Pendakur's chapter, non-motorized transport is the starting point of analysis, for transport efficiency and transport equity matters alike. Urban transport planning is often technocratically framed as 'apolitical intervention' (Eduardo Vasconcellos), where in fact it is top income segment who by driving their cars consume 10 times more space than the urban poor, consume a largest part of transport energy, and are responsible for most of street-level air pollution. It is then quite clear that a suitable normative objective for urban transport is reasonable accessibility for all, possibly emphasizing the urban poor (the concept itself actually may need to be qualified, see Xavier Godard's chapter). Accesssibility itself is a highly interesting concept: Some cities, such as Dakar, seem to have high accessibililty - walkability - for the poorest quantile. In contrast, in cities like Buenos Aires the lowest income quintile pays proportionally to income much more than the richest quantile. Poverty may also directly reduce social contact by rendering visits to family or friends infeasible.

In line of the this comprehensive analysis, it then follows naturally to require comprehensive assessments of urban transport projects and plans, relying on strategic environmental assessments (Michael Replogle), inclusive equity evaluation (Eduardo Vasconcellos), and context-specific economic appraisal (Walter Hook). The key conundrum, however, is then in the meta-level of institions (Elliott Sclar and Julie Touber). In the dense urban environment of Asian and many African cities, the traffic disaster of the Bangkok syndrome can only be tackled with efficient public transport. But public transport can be regarded as a quasi-public good, and will not emerge from demand-side focussed market outcomes. Hence institutional capacity, a governance framework of promoting public goods and better public transport and non-motorized transport system need to coevolve simultenously. Transport planning alone is not enough.