Many people live in cities today. Many more will do so in future. This increases the demand for space and (space for) transport. Space to expand roads is usually scarce. Building tunnels or elevated bridges is very expensive. Solving one bottleneck creates another bottleneck downstream. More road infra- structure leads to more cars and more cars to more congestion and externalities. Megacities invest in large-scale (preferably underground) public transport while smaller cities lack the required number of travellers and the money to warrant the high investment costs. In a sustainable city, the supply of goods, services, water, energy and transportation should differ from the current practice. New technologies in car manufacture are interesting, in particular, the nearly roadworthy self-driving (autonomous) cars. It is still a demanding challenge to let these share roads with conventional cars, cyclists and pedestrians. Currently, cities lack the space for a separate network for these cars. A socially challenging alternative would be to replace all private cars by shared electric self-driving cars and small shuttle buses and inte- grate these with mass transport, cycling and walking. Passenger transport would need much less space for driving and parking. Congestion will vanish. Local air pollution, noise and use of resources to pro- duce cars and road materials will be reduced. Reclaimed space can be used to create a more sustainable and social environment and to optimize city logistics. The building blocks of such a (public–private)system exist already or will become available in the future.
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