Abstract

The harmonious development of cities is a key problem of our times. Is it possible to have sustainable urban areas that enhance rather than diminish the standard of living of their inhabitants? To better understand the issues behind this question, we begin by defining sustainability and the factors that should be associated with a sustainable urban development. We then consider urban mobility, focusing on one of its major challenges: vehicle congestion. With a view to devising possible solutions to the congestion challenge, we characterize it using basic tools from the field of traffic management and engineering. This reveals that, as with many other problems, apparently common sense solutions do not work, and in particular that congestion cannot be solved by road infrastructure construction alone. In this context, we also discuss two paradoxes that reinforce the idea that "obvious" solutions do not work, and outline certain phenomena suggesting that the worst enemy of urban sustainability is the indiscriminate use of private cars in congested scenarios. We then argue that urban development and mobility are wicked problems in organized complexity and, as such, do not have completely satisfactory solutions. In this light we propose what we believe has become the most consensual solution among specialists: a stick and carrot approach. The stick is a policy such as road pricing that charges for using cars in urban areas during congested periods, while the carrot consists of a good public transport system. Finally, we caution that this approach is unlikely to be implemented unless there is a political champion who is prepared to lead longer-term strategies that can capture the enthusiasm of the citizenry.