''"The definition of an urban area is an extent of at least 20 hectares and at least 1,500 residents at the time of the 2001 Census. The starting point is the identification by OS (Ordnance Survey) of areas with land use which is irreversibly urban in character. This comprises permanent structures and the land on which they are situated, including land enclosed by or closely associated with such structures; transportation corridors such as roads, railways and canals which have built up land on one or both sides, or which link built-up sites which are less than 200 metres apart; transportation features such as airports and operational airfields, railway yards, motorway service areas and car parks; mine buildings, excluding mineral workings and quarries; and any area completely surrounded by builtup sites. Areas such as playing fields and golf courses are excluded unless completely surrounded by builtup sites. The prerequisite for the recognition of an urban area is that the area of urban land should extend for 20 hectares or more. Separate areas of urban land are linked if less than 200 metres apart. Land between built-up areas is not regarded as urban unless it satisfies one of the conditions listed above."''〔(ONS definition of urban areas )〕