The methodology used by ONS in 2011 is set out in 2011 Built-up Areas – Methodology and Guidance, published in June 2013. When ONS reported the results of the 2011 UK census, it used the term "built-up area" rather than the term "urban area" as used in previous censuses. ONS states, however, that the criteria used to define "built-up area" have not changed:
the definition follows a ‘bricks and mortar’ approach, with areas defined as built-up land with a minimum area of 20 hectares (200,000 m2), while settlements within 200 metres of each other are linked. Built-up area sub-divisions are also identified to provide greater detail in the data, especially in the larger conurbations.
In reporting the 2001 census, ONS gave a clearer definition of the term "built-up" as follows:
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...
List of most populous urban areas
The list below shows the most populated urban areas in the United Kingdom as defined by the Office for National Statistics (ONS), but as readily referenced at Citypopulation.de. The list includes all urban areas with a population in excess of 100,000 at the 2011 census.
- ONS definition. Excludes motorways, rivers, lakes, parks and other open space, even if fully contained but wider than 200m.:10
- ONS definition.:6
- These 'metropolitan area' definitions were created by ESPON with the intent to create a pan-European model. They were not defined by the ONS and have no official status. The list has not been refreshed after subsequent censuses.
- Some of the names of subdivisions and the areas they represent have changed between the two censuses. So it may look as though an area has become part of a built-up area between the two censuses but it may have already been part of the 2001 urban area but was included under a different subdivision.
- The urban sub-area that the ONS has called 'Milton Keynes' is actually just the northern 80% (approx) of Milton Keynes proper. The ONS has separated out Bletchley (which is about 20% of MK) for reasons that are not explained.
- Stapenhill and Winshill were treated as a separate urban area in the 2001 census but in the 2011 census they were treated as part of the Burton-upon-Trent subdivision.
- Office for National Statistics, 2011 Built-up Areas – Methodology and Guidance, p.3 Archived 21 September 2013 at the Wayback Machine
- ONS definition of urban areas Archived 27 March 2009 at the Wayback Machine
- "United Kingdom: Urban Areas". Citypopulation.de. Retrieved 31 December 2014.
- "2011 Census – Built-up areas". ONS. Retrieved 1 July 2013. (needs a more direct citation)
- http://www.espon.eu/export/sites/default/Documents/Projects/ESPON2006Projects/StudiesScientificSupportProjects/UrbanFunctions/fr-1.4.3_April2007-final.pdf#page=122 Archived 24 September 2015 at the Wayback Machine
- Census 2001 Key Statistics, Urban areas in England and Wales Office of National Statistics
- UK Census (2011). "Local Area Report – Milton Keynes BUA Built-up area (E34005056)". Nomis. Office for National Statistics. Retrieved 29 March 2019.