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]

Contents 1 List of the 25 largest urban areas in the UK 2 Commentary 3 See also 4 References

[edit] List of the 25 largest 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).

Rank	Urban Area[2]	Population (2001 Census)[2]	Localities[3][4]	Area (km²)[2]	Density (People/km²)[2]	Major localities[3][4]
1	Greater London Urban Area	8,278,251	67	1,623.37	5,099.4	London (dozens of localities of broadly similar size)
2	West Midlands Urban Area	2,284,093	22	599.72	3,808.6	Birmingham, Wolverhampton, Dudley, Walsall
3	Greater Manchester Urban Area	2,240,230	57	556.72	4,024.0	Manchester, Salford, Bolton, Stockport, Oldham, Rochdale, Bury, Wilmslow
4	West Yorkshire Urban Area	1,499,465	26	370.02	4,052.4	Leeds, Bradford, Wakefield, Huddersfield
5	Greater Glasgow	1,168,270	48	368.47	3,171.0	Glasgow, Paisley, Coatbridge, Clydebank, Motherwell
6	Tyneside	879,996	25	210.91	4,172.4	Newcastle upon Tyne, North Shields, South Shields, Gateshead, Jarrow
7	Liverpool Urban Area	816,216	8	186.17	4,384.4	Liverpool, Bootle, Litherland, Huyton, Roby, Crosby, Prescot, St. Helens, Haydock
8	Nottingham Urban Area	666,358	15	158.52	4,203.6	Nottingham, Beeston and Stapleford, Carlton, Long Eaton
9	Sheffield Urban Area	640,720	7	162.24	3,949.2	Sheffield, Rotherham, Chapeltown, Mosborough/Highlane
10	Bristol Urban Area	551,066	7	139.78	3,942.4	Bristol, Kingswood, Mangotsfield, Stoke Gifford
11	Greater Belfast	483,418	7[5]	161.67	2,990.2	Belfast, Castlereagh, Greenisland, Holywood
12	Brighton/Worthing/Littlehampton	461,181	10	94.09	4,901.5	Brighton, Worthing, Hove, Littlehampton, Shoreham, Lancing
13	Edinburgh	452,194	2	120.11	3,765.0	Edinburgh, Musselburgh
14	Portsmouth Urban Area	442,252	7	94.52	4,678.9	Portsmouth, Gosport, Waterlooville, Fareham
15	Leicester Urban Area	441,213	12	101.64	4,340.9	Leicester, Wigston, Oadby, Birstall
16	Bournemouth Urban Area	383,713	5	108.15	3,548.0	Bournemouth, Poole, Christchurch, New Milton
17	Reading/Wokingham Urban Area	369,804	5	93.17	3,969.1	Reading, Bracknell, Wokingham, Crowthorne
18	Teesside	365,323	7	113.99	3,204.9	Middlesbrough, Stockton-on-Tees, Redcar, Billingham
19	The Potteries Urban Area	362,403	3	96.62	3,750.8	Stoke-on-Trent, Newcastle-under-Lyme, Kidsgrove
20	Coventry/Bedworth Urban Area	336,452	3	75.56	4,452.8	Coventry, Bedworth, Exhall
21	Cardiff Urban Area	327,706	4	75.72	4,328.0	Cardiff, Penarth, Dinas Powys, Radyr
22	Birkenhead Urban Area	319,675	5	89.11	3,587.4	Birkenhead, Ellesmere Port, Wallasey, Bebington
23	Southampton Urban Area	304,400	3	72.80	4,181.3	Southampton, Eastleigh, Bishopstoke
24	Kingston upon Hull	301,416	1	80.44	3,747.3	Kingston upon Hull
25	Swansea Urban Area	270,506	4	79.81	3,389.0	Swansea, Neath, Port Talbot, Pontardawe/Clydach

[edit] Commentary

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, Wokingham, and 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 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: 312,521. 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.

In Merseyside there is a split between Liverpool Urban Area and the Birkenhead Urban Area. Both of these localities are thought by many to be Greater Merseyside as only the distance of the river Mersey separates them. This gives a population of 1,135,891. Where the Newcastle/Gateshead conurbation claims both sides of the river, Liverpool does not. The Liverpool Urban Area is also disputed, excluding the nearby localities of Widnes and Runcorn in Halton, which are part of the Liverpool City Region, and further to the north Southport and Warrington which could be justified on the same grounds, if not with more depth than Mancunian claims to Bolton and Rochdale.

[edit] See also

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

[edit] References