Alienation leads to conflict, graffiti, vandalism, mugging, theft etc. Urban layouts can either encourage alienation or help people to make contact with each other. Multiplicity of use keeps all parts active. The philosophy that, to regenerate derelict areas, we must provide ideal conditions for commercial development is the most destructive policy for a city's social equilibrium. Good urban layouts can provide the 'passive' social contact that stands alongside the 'active' efforts of clubs, agencies, churches etc.
Most informal contact happens when people are walking.
City life is dependent on people walking. Only recently have people been forced off the street by cars. On foot you need to feel you are in a designed 'place', you need a sense of enclosure. The surrounding walls need doors and windows so that the spaces are overlooked and full of movement . You need direct routes - an extra quarter of a mile really matters when walking or in a wheelchair.