How can universality, or yellowness, be re-engineered into cities? Is it desirable or even achievable? Conventional urban planning has rarely succeeded in creating universal access to services or economic opportunity, and in fact has contributed to the legacy of fragmented cities. Public services are no longer monopolies. Transport, health, schools, water, electricity, telephone, but also public space, urban development, and new infrastructure are increasingly privatised or market-led. In most cases the balance-sheet benefits from the efficiencies of private-sector management. However it also often dispenses with the cross-subsidies involved in providing for the ‘public good’, ‘common interest’, or ‘social overhead capital’. The consequence is the break-up of the social and infrastructural continuities of the city. Some districts and people are literally by-passed by improvements. Streets are disconnected and the grid of city streets is eroded.

These phenomena are recognised in cities the world over. Urban scholars have theorised these changes in different ways. The ‘splintering metropolis’ is a city of fragments separated by physical boundaries and differentiated by their level of access to services, infrastructure, and opportunity. ‘Tectonic multiculturalism’ describes the city of enclaves defined by group identities of class and ethnicity, whose shifting boundaries create periodic frictions and quakes. The ‘archipelago economy’ is a world of prosperous islands interlinked across a sea of economic underperformance. Each of these describes in its own way an urban patchwork of isolated differences which are rarely negotiated.