Road classification: how does it work?

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There are three systems through which roads are organised and classified nationwide – the strategic road network, the primary route network and roads classification.

The responsibility for classification of the Strategic Road Network (SRN) lies with National Highways.

Since 2012 local highway authorities have had greater responsibility in the management of the roads classification system without the need for central approval. Similarly local highway authorities also  have greater responsibility in the management of the Primary Road Network (PRN).

The Primary Road Network (PRN) is constructed from a series of locations (primary destinations) selected by the Department for Transport, which are then linked by roads (primary routes) selected by the local highway authority.

A list of primary destinations in England can be found in Annex A of the DfT Guidance on Road Classification and the Primary Road Network. (Link here)

All UK roads (excluding motorways) fall into the following 4 categories:

  • A roads – major roads intended to provide large-scale transport links within or between areas
  • B roads – roads intended to connect different areas, and to feed traffic between A roads and smaller roads on the network
  • classified unnumbered – smaller roads intended to connect together unclassified roads with A and B roads, and often linking a housing estate or a village to the rest of the network. Known unofficially as C roads
  • unclassified – local roads intended for local traffic. The vast majority (60%) of roads in the UK fall within this category

Road Class indicates the class of the road upon which a crash occurred. The letter designating each type of classified road forms a prefix to its number.

  • Motorway
    • M
    • A(M)
  • Main
    • A
    • B
  • Minor
    • C
    • Unclassified
  • Unknown

In STATS19, for crashes at junctions which cannot clearly be allocated to one specific road, the class of the main road is entered. The main road is defined as the road which has priority. For roundabouts and signal controlled junctions, the main road is the one with the highest class of all the roads entering the junction. If roads are of equal class then the road with the lowest number is taken as the main road.

Service roads are recorded as Unclassified, not with the class of the main road alongside which they run.

Individual highways authorities can determine whether they wish to classify C roads separately from Unclassified roads. For this reason, this distinction cannot be relied upon nationwide.


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