Scottish Government Urban Rural Classification 2020

3. Methodology

Data Sources

The Scottish Government Urban Rural Classification 2020 was created by combining population and accessibility information to distinguish between urban and rural areas across Scotland. Population information is sourced from the Settlements dataset provided by National Records of Scotland (NRS), and accessibility information is obtained by calculating drive times from the centres of Settlements with a population of 10,000 or more (i.e. Large and Other Urban Areas). Table 3.1 summarises the datasets used to create the 2020 version of the classification.

Settlements define built-up areas in Scotland, and are generally more identifiable as the traditional towns and cities than administrative boundaries such as Council Areas, much of which consist of land that is not developed and unpopulated. The Settlements dataset is produced by NRS, with the current version (Settlements 2020) having been released in March 2022. Small Area Population Estimates, together with information from the Royal Mail Postal Address File, were used to classify 2020 postcodes as high or low density. A Settlement is defined to be a group of high density postcodes whose combined population rounds to 500 people or more. They are separated by low density postcodes. For more information on how Settlements are created, see the NRS website.

Settlement centroids for Carlisle and Berwick-upon-Tweed in Northern England were also included in the analysis as they have populations of over 10,000 and are within a 30-minute drive of the Scottish border, and thus will influence accessibility results. For consistency, the same centroids which were used in 2013-14 and 2016 Classifications were used in the 2020 analyses. These were based on the OS 50k Gazetteer product.

Transport Network Creation

For the calculation of drive times, a network dataset including road and ferry routes was required. Roadways were obtained from Ordnance Survey (OS) MasterMap Highways (RAMI and Paths) for Scotland with an extension beyond the border to include routes for Northern England. OS Highways gives a current, comprehensive network view of Great Britain's roads. In the previous 2016 Classification, another OS product - Integrated Transport Network (ITN) - was used. This network dataset has since been retired.

The Scottish Government maintain a dataset of Scotland's ferry routes which have been digitised against OS background mapping. Both vehicle and passenger only services are included in the SG Ferry Routes, though only the vehicular routes are used within the Urban Rural analysis.

A network dataset was built from the road and ferry networks, and each road type was assigned an average speed, shown in Table 3.1. Settlement 2020 boundaries identified whether the rural or urban speed was applied. For example, motorways would have been assigned an average speed of 104.6 kph in rural areas, and 70.8 kph in urban (built up) areas. It should be noted that the process does not take into account peak and non-peak travel times; the speeds for each road type are the average for that class^[1]. For consistency, the figures used for the 2020 analyses match those used in the 2016 and 2013-14 Classifications.

The ferry speeds were already available on the Scottish Ferry Routes dataset, calculated from the online timetables, and a standard 30-minute boarding time was added for the drive times.

Analysis and Classification

The first stage in creating the classification is to categorise the Settlements dataset using the population thresholds of 125,000, 10,000 and 3,000 to identify the Settlements from which drive times will be calculated. Settlements were grouped into the following categories:

(1) Large Urban Areas - populations of 125,000 or more

(2) Other Urban Areas - populations of 10,000 to 124,999

(3) Small Towns - populations of 3,000 to 9,999

(4) Rural Areas - populations less than 3,000

The next step was to distinguish between accessible and remote areas. The drive times were calculated from the centroids of the Settlements with a population of 10,000 or more (i.e. Large and Other Urban Areas). The drive time analysis was performed using GIS software (ESRI ArcGIS Pro Network Analyst extension). The following definitions of remoteness were defined:

(1) Accessible – areas within a 30 minute drive time of a Settlement with a population of 10,000 or more.

(2) Remote – areas that are more than a 30 minute drive time (6-fold classification), or areas that have a drive time more than 30 minutes but less than or equal to 60 minutes (8-fold classification) from a Settlement with a population of 10,000 or more.

(3) Very Remote – areas that are more than a 60 minute drive time from a Settlement with a population of 10,000 or more (8-fold classification only).

Accessibility categories were assigned to the Settlement boundary layer based upon the location of the Settlement population weighted centroids. Classifying the settlements by their centroids means that the entire settlement will be assigned to a single class, regardless of whether the area is split by the drive time extent boundary.

The re-classified settlement boundaries and drive time datasets were combined to form one national dataset containing the 2, 3, 6 and 8-fold urban rural definitions. All layers were clipped to both the Mean High Water and Extent of the Realm coastlines.