ABSTRACT
Whilst there are several types of linkage, most commentators on this topic have used commuting flows as an indicator of metropolitan allegiance. For Britain it was decided to include all districts which sent at least 10 percent of their resident workforce into the conurbation. In reality the task of dividing an urban region into concentric zones using existing administrative divisions is neither easy nor produces the zones required in many cases. Since the late-1970s Baltimore has been widely acclaimed as an example of a successful city revitalisation which has attracted numerous urban experts and attempts at imitation. For most of its history Baltimore has been a port and industrial centre, with its regional role limited by the proximity of Washington, 66 kilometres to the south-west and Philadelphia, 160 kilometres to the north-east. To many people Pittsburgh is the epitome of a smokestack city in the American Rustbelt which is suffering from the rundown of its basic industries.
