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UK Roads

From bustling cross-country motorways to less travelled country lanes, public roads in the UK are differentiated by a letter and one or more numbers in combination. These designations reflect the nature of the road, the destinations they link, and the typical traffic density along the route. They also assist with navigation.

Road Network

Roads are classified as trunk roads and non-trunk roads. Trunk roads are routes of national importance. They are maintained by the national highway authorities of England, Scotland, Wales and Northern Ireland. For example, the Highways Agency maintains trunk roads within England. Other public roads or non-trunk roads are maintained by local authorities, such as a county or city council. All maintenance costs for trunk roads are paid for by the central government, while costs for other roads are cost-shared between local authorities and the central government.

Roads are classified in three tiers: motorways, A-roads and B-roads. Additional designations may also be assigned by local authorities, although they generally do not appear on maps or signs. With the exception of M designated motorways, numbers for roads are based on designated zones throughout Britain. For example, roads in Zone 3 are numbered A3, A32 and A351. Motorways are generally numbered based on zone boundaries in England and Wales, while in Scotland they are assigned the number of the pre-existing A-road the motorway replaced.


Motorways are controlled access dual carriageway roads, also known as freeways or highways in other parts of the world. They are designed with an M prefix, such as M1 or M4. Some A-roads designed as motorways are assigned a (M) suffice, such as the A1(M). The speed limit on motorways is typically 70 miles per hour, or 110 km/h. Signs on motorways indicating destinations and directions are blue with white text. A hard shoulder is typically present. Motorways also feature emergency telephones to assist motorists during a breakdown or collision. Cyclists, pedestrians and certain vehicles, such as slow vehicles and mopeds, are not permitted on motorways.

Junctions at regular intervals provide access to and from a motorway. Junctions are typically numbered, although they may also feature a letter suffix. They are identified with signs approximately one mile before the exit, with additional signs placed at regular intervals until the exit. A junction’s designation (for example, J5 for Junction 5) is identified in a small black box on all signs for the junction.

The UK's first full length motorway was the M1. Today, most major cities and towns in the United Kingdom are linked by a motorway. There are 49 numbered motorways in England, Scotland and Wales, including one toll motorway (M6 Toll) near Birmingham. In addition, there are 17 upgraded primary A-roads with designations as motorways. In Northern Ireland, there are 6 M-designated motorways and one primary A-road designated as a motorway.


A non-primary A-road is located near a main or primary recommended route, such as a primary A-road or motorway. Non-primary A roads duplicate the function of primary routes. On maps they are distinguished by red lines. Signage is white with black letting. By comparison, primary A-roads are labelled green on maps and signs. These roads are main routes and are typically single or dual carriageways. All primary roads in the UK are fully connected.

Most A-roads have clearway restrictions where street parking is limited or not permitted. In large cities, primary A-routes may also be categorised as red routes. Vehicles along red routes are not permitted to stop or stand for any purpose. These routes are often used as bus and commuting corridors. Red routes are distinguished by red lines along the sides of the road. A double red line indicates that stopping prohibitions apply at all times, while single red lines means that regulations apply at certain times as indicated on signs on the route. Most red routes in the UK are found in London and West Midlands.

In England and Wales, primary A-roads feature single digit numbers. Primary A-roads include the A1 between London and Edinburgh, the A2 from London to Dover, the A3 between London and Portsmouth, the A4 from London to Avonmouth, and the A5 from London to Holyhead. Other primary A-roads include the A6 from Luton to Carlisle, the A7 between Edinburgh and Carlisle, the A8 from Edinburgh to Greenock, and the A9 between Falkirk and Scarbster. Primary A-roads are supplemented by two-digit route numbers. Although still major routes, they are largely secondary to primary A-roads. A-roads with three and four digit numbers are typically newer routes. The lower the number, the closer the origin is to London. Certain A-roads are designed as trunk roads and motorways. Sections where an A-road is recognised as a motorway will include the suffix (M), such as A3(M) and A627(M).


B-roads are local routes with less traffic when compared to A-roads. They are often regional in nature and are identified as brown or yellow routes on maps. White and black signage along B-roads are similar to non-primary A-roads. B-roads can range from one-lane roads to dual carriageways. They are numbered similar to A-roads with one to four digits, although most B-roads have 3 or 4 number designations.

Other Designations

Roads and lanes with low traffic are assigned C, D or U. U-roads are also known as unclassified roads. These designations are typically assigned by local authorities and generally do not appear on public signage. These routes are generally not illustrated on maps. Designation is often arbitrary, as determined by local decision-makers.