Roads in The United Kingdom - Classification

Classification

Roads in the UK are classified into M (Motorway), A, and B roads. For internal purposes, Local Authorities may also use C, D and U (the latter standing for 'Unclassified'). Each road is given a number which is combined with the prefix, for example M40, A40 and B1110. Roads in Great Britain are numbered according to a zonal system. There is no available explanation for the allocation of road numbers in Northern Ireland. Motorways are used for the majority of the major inter-urban routes and are designed to carry long distance traffic. Between them is the primary route network, which are A roads. A primary route is defined as:

...a route, not being a route comprising any part of a motorway, in respect of which the Secretary of State —

(a) in the case of a trunk road is of the opinion, and

(b) in any other case after consultation with the traffic authority for the road comprised in the route is of the opinion,

that it provides the most satisfactory route for through traffic between places of traffic importance