Guidance

Road lengths in Great Britain statistics: Notes and definitions

Updated 21 March 2024

Applies to England, Scotland and Wales

These notes and definitions relate to the road length statistics published on the Department for Transport website. For further information on these statistics please email road length statistics.

Road length estimates are produced using information from Ordnance Survey’s Highways Network dataset, local authorities, the Scottish Government, the Welsh Government and National Highways (formerly Highways England). The majority of the data relate to a single time point of April of the year in question.

Types of road

Major roads

Includes motorways and all ‘A’ roads. These roads usually have high traffic flows and are often the main arteries to major destinations.

Motorways (built under the enabling legislation of the Special Roads Act 1949, now consolidated in the Highways Acts of 1959 and 1980). Includes major roads of regional and urban strategic importance, often used for long distance travel. They are usually 3 or more lanes in each direction and generally have the maximum speed limit of 70 miles per hour.

‘A’ roads

These can be trunk or principal roads. They are often described as the ‘main’ roads and tend to have heavy traffic flows though generally not as high as motorways.

Trunk roads (designated by the Trunk Roads Acts 1936 and 1946)

Most motorways and many of the long distance rural ‘A’ roads are trunk roads. The responsibility for their maintenance lies with the Secretary of State and they are managed by National Highways (formerly Highways England) in England, the Welsh Government and the Scottish Government (National Through Routes).

Non-trunk roads

These are roads for which local highway authorities are responsible. Non-trunk roads are either classified or unclassified, the former being of 2 types, principal and non-principal. The classified principal roads are class ‘A’ roads, plus a small amount of local authority motorway, and are of regional and urban strategic importance. The non-principal roads are those which distribute traffic to urban and regional localities. The non-principal classified roads are sub-divided into ‘B’ and ‘C’ classes. Unclassified roads are those in the least important categories, such as local distributor and access roads.

Principal roads

These are major roads which are maintained by local authorities. They are mainly ‘A’ roads, though some local authorities do have responsibility for some motorways.

Minor roads

These are ‘B’ and ‘C’ classified roads and unclassified roads (all of which are maintained by the local authorities), as referred to above. Class III (later ‘C’) roads were created in April 1946. ‘B’ roads in urban areas can have relatively high traffic flows, but are not regarded as being as significant as ‘A’ roads, though in some cases may have similarly high flows.

They are useful distributor roads often between towns or villages. ‘B’ roads in rural areas often have markedly low traffic flows compared with their ‘A’ road counterparts. ‘C’ roads are regarded as of lesser importance than either ‘B’ or ‘A’ roads, and generally have only one carriageway of 2 lanes and carry less traffic. They can have low traffic flows in rural areas. Unclassified roads include residential roads both in urban and rural situations and rural lanes, the latter again normally having very low traffic flows. Most unclassified roads will have only 2 lanes, and in rural areas may only have 1 lane with “passing bays” at intervals to allow for 2-way traffic flow.

Urban roads

These are major and minor roads that sit within a built up area, with a population of more than 10,000 in England and Wales or more than 3,000 in Scotland.

Rural roads

These are major and minor roads that sit outside urban areas (these urban areas have a population of more than 10,000 people in England and Wales or more than 3,000 in Scotland).

Private roads

For the purpose of this publication, private roads are considered to be road not maintained at public expense. For major roads, private roads (usually toll roads, tunnels and bridges) are included in the road length figures as they are accessible to the general public. For minor roads, private roads are not included in the road length figures as they are not usually accessible to the general public.

Types of road in Great Britain

The diagram below shows the road types that make up trunk and principal, and major and minor roads. Trunk roads are always major roads and are referred to in these statistics as trunk motorways and trunk ‘A’ roads. Principal roads can be major roads, referred to as principal motorways and principal ‘A’ roads, or they can be minor roads, referred to as ‘B’ roads, ‘C’ roads and ‘U’ roads.