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A conurbation is formed when towns expand sufficiently that their urban areas join up with each other. This process has happened many times in the United Kingdom. Green Belts were introduced in the 20th century to try to prevent urban sprawl and so stop new conurbations forming.

In many cases, there are differences of interpretation as to the limits of a conurbation - where it begins and ends. For the purposes of consistency, the list on this page sets out urban areas as defined by the Office for National Statistics (ONS).

The ONS definition of an urban area is based on the continuously built-up area, and is as follows:-

"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."^[1]

List of major urban areas in the UK

The list below shows the most populous urban areas in the UK as defined by the Office for National Statistics (ONS).

Commentary

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There is a spectrum that can be drawn between the conurbations that have a clear 'head' (such as Nottingham, Southampton) to those that do not - known as multi-centred conurbations (such as Bournemouth/Poole and Teesside) - via ones that are more borderline (West Midlands). In the case of the West Midlands, for example, the largest city, Birmingham did expand massively and is now considered to include areas that were formerly independent towns, such as Sutton Coldfield and Aston. However, here it stopped, with the Black Country and Wolverhampton retaining strong identities.

In various parts of the country are more borderline cases, where the areas expanded into did not necessarily have strong identities as towns. However, the areas do retain separate local government structures, and are therefore considered conurbations by the ONS, on this basis :

• Bristol urban area - Bristol, Kingswood, Longwell Green, Mangotsfield, Frenchay, Downend, Filton, Bradley Stoke, Patchway, Cribbs Causeway
• Greater Leicester, including Birstall, Syston, Oadby and Wigston, Glenfield, Braunstone
• Reading/Wokingham Urban Area - including Reading, Purley-on-Thames, Wokingham, Bracknell

There are also various places where whilst not actually running into each other, the amount of development in a large area is substantial. Heavily built up areas of this type include :

• South Hampshire, consisting of the Portsmouth and Southampton areas mentioned above, was considered for metropolitan county status in the 1970s
• West Yorkshire and South Yorkshire, which are both heavily built up but not entirely devoid of countryside (both are metropolitan counties)
• Cardiff/Newport, consisting of the cities of Cardiff and Newport, Cwmbran, much of the eastern South Wales Valleys with towns such as Risca, Ebbw Vale, Pontypool and Caerphilly and part of the Vale of Glamorgan including Penarth and Barry.

The entire Merseyside/Warrington/Greater Manchester area (2821sq km) is not much bigger than West Yorkshire (2029sq km) but has a population topping 4 million in comparison to the 2.5 million of West Yorkshire. There are gaps of countryside between towns on the way from Liverpool to Manchester, but not especially big ones. The area between is protected as part of a Green Belt, to stop the conurbation proceeding further.

The metropolitan county of Tyne and Wear is almost a quarter of the size of West Yorkshire, but the two main settlements (Newcastle/Tyneside and Sunderland/Wearside) are not part of the same conurbation due to the fact that a gap of countryside exists between South Tyneside and Sunderland, but this gap is fairly small. If these two conurbations were counted as one, the population would be 1,182,517 with Wearside containting the settlements of Sunderland, Washington and Seaham, population: 302,521. Newcastle's urban area also extends northwards into Northumberland with settlements such as Cramlington and Blyth potentially increasing the Tyneside and Wearside urban area further.

Smaller examples of conurbations also exist on a more local level. For example, Harrogate runs into Knaresborough, Warwick runs into Leamington Spa, Luton runs into Dunstable, and Grimsby runs into Cleethorpes.

See also

• List of largest United Kingdom settlements by population
• Metropolitan areas of Ireland

References