The fundamental dilemma in attempts to make urban development less dependent upon mobility by car is the inability of alternatives to match the quality of accessibility provided by private motorized transport. Failure to recognize this means that bringing about environmentally more sustainable urban mobility patterns is only possible at economic, social, and political costs that are unacceptable in most societies. In this paper we identify and discuss ways out of this dilemma, in the form of solutions that pursue the goal of increasing both sustainability and accessibility. We start by contending that what people ask is not a generic mobility, but rather opportunities to participate in spatially disjointed activities. Accordingly, accessibility should be defined as the amount and the diversity of 'spatial opportunities' that can be reached within a certain amount of time. Solutions to the accessibility-sustainability dilemma building upon this perspective (that is, planning concepts, policy measures) have been the object of recent research at the Universiteit van Amsterdam and are discussed and we look for, and find, evidence of the feasibility of these solutions in the actual trends in the Amsterdam urban region. Some policy implications of the findings are discussed.
