Sustainable urban mobility, an evolutionary approach

The sustainable mobility approach has many merits. However, and particularly when applied to cities, it also tends to show a lack of recognition of the intrinsic difficulty of change in real-world land use and transport systems. A complementary, evolutionary approach to urban transport planning is introduced in this article as a possible answer to this shortcoming. The focus is not so much on the identification of relevant problems and potential solutions but rather on the challenge of actually bringing about change in an existing, by definition uncertain situation. Examples from the Netherlands illustrate the discussion. There are two main conclusions. The first is that there is a need to better understand the constraints to and opportunities for change determined by local specificities and histories. The second is that it is essential to enhance adaptability and resilience of the urban land use and transport system. Introduction: sustainability and change For urban transportation planners these are exciting, but also greatly daunting times. On one side, and in spite of all the hype about dematerialization, transport and other technical networks appear ever more crucial in granting individuals and organizations the access to the increasingly spatially dispersed resources they need to thrive or even just to survive. Successful metaphors as ‘network society’ (Castells, 1996) or ‘age of access’ (Rifkin, 2000) underline this. At the same time, because of an heterogeneous mix of financial and fiscal constraints, environmental awareness and social resistance, the modern ideal of ubiquitous access is being superseded by a much more targeted, largely market and special interest driven transport infrastructure development, effectively ‘splintering’ cities (Marvin and Guy, 1999; Graham & Marvin, 2001). The resulting picture is that of a growing societal complexity of choices regarding the planning and design of urban transportation networks, which can less and less be regarded as simple technical endeavours. An approach is needed where the existence of conflicting claims to the expansion of transport systems becomes apparent, where technological possibilities and constraints are made visible and debatable, and where the broader economic, social and environmental implications of choices can be addressed. The increasingly popular sustainability-centred approach would seem to go in the right direction, particularly in its most recent, more comprehensive versions. In general terms, the sustainability approach has moved away from an original focus on the preservation of natural resources and towards a broader interpretation of sustainability that also involves economic and social aspects. As far as urban transport is concerned, the negative effects of mobility (energy use, CO2 emissions, air pollution, traffic noise, etc.) are typically weighted against the access mobility provides to organizations and individuals (for instance in terms of labour, clients and business relations, or of jobs, services and personal contacts). Following this line of reasoning, a sustainable solution is one that strikes a balance between the positive and negative effects of the urban transport system. Accordingly, most approaches to sustainable urban mobility set the task in terms of optimisation: how to maximise benefits and minimize costs? Policy documents are typically worded along this line. This is the case even when benefits and costs are defined in a broad fashion, that is, including both economic, social and environmental aspects, and both items that can and cannot be easily given a price tag. In a characteristic passage, WBCSD (2001, pp. 1-7) contends for instance that “For mobility to be sustainable, it must improve accessibility while avoiding disruptions in societal, environmental, and economic well-being that more than offset the benefits of the accessibility