Trunk roads in Ireland

A trunk road was a road in the Republic of Ireland of the highest classification between 1926 and 1977. The lower classifaction of main road was termed a link road. Trunk and link roads were identified by numbers prefixed with the letter T or L respectively; lesser roads had no such identifiers. In 1977 the classification was changed to national primary and secondary, regional, and local roads. Typically, each segment previously classified as trunk or link respectively became national or regional, but the numbering was done on a new basis.

The UK's Ministry of Transport Act 1919 said that the British Minister of Transport "may, after consultation with the Roads Committee ... and the local authorities affected, classify roads in such manner as he thinks fit". The Irish Free State's Minister for Local Government and Public Health inherited this power under the Ministers and Secretaries Act 1924. The Local Government Act 1925 classified each road as a "main road", "county road", or "urban road", depending on whether they were to be funded by ratepayers of the whole county, the rural area, or the urban area respectively; only the minister could designate main roads. In December 1925 the minister made a "Main Roads Order" for each administrative county in consultation with its local authorities, designating certain roads as main roads, each numbered as a "Trunk" or "Link" road. A 1926 order provided that road signs should display "the route letter and number" assigned by the minister, and that 'the expression "Main Road" [in the 1919 act] included a road classified ... as a "Trunk" or "Link" Road.' A 1964 parliamentary answer described the Main Road Order process:

Subsequently, in the period 1925–26, a further classification of roads was made pursuant to the Local Government Act, 1925, into main, county and urban roads, for the purpose of apportioning statutory responsibility for construction and maintenance, and for determining the chargeability of roads expenses for the purposes of annual estimates. The 1925 Act classification, like the 1919 Act classification, was also made after consultation with the local authorities, and the roads which were declared to be main roads were the trunk and link roads of the 1919 Act classification together with some additional roads decided upon after the consultation which I have mentioned.

Even though legal authority for the erection of directional signposts was given to local councils, the Automobile Association of Ireland began an extensive road signposting scheme in 1938 which included comprehensive signposting of routes from Belfast, Cork and Dublin. Evidence that the Trunk Road and Link Road classification and numbering system had been well established by the 1950s is found in the Traffic Signs Regulations, 1956 which contains examples of several directional signs. The first and second examples show the T8 as the route to Wexford and Rosslare. In addition, Esso road-maps of Ireland from the 1950s show the Trunk and Link road network.

This current system of road classification and numbering has its origins in the late 1960s: the Minister for Local Government, Kevin Boland, announced on 23 July 1969 that a national road network would be formed, to be planned and funded by central rather than local government. The Local Government (Roads and Motorways) Act 1974 allowed for designation of roads as motorways or national roads. National roads were first designated on 1 June 1977. Twenty-five National Primary routes (N1-N25) and thirty-three National Secondary routes (N51-N83) were initially designated. Sections of national roads upgraded to motorway status would use letter M instead of N in the identifier (beginning in 1983).

The changeover to the new system was gradual: a route planning map of Ireland from the late 1970s (or early 1980s) shows a mixture of Trunk Road, Link Road and National route numbers.

Major roads within the Republic of Ireland were marked with "T" for Trunk Road, less important roads were marked with "L" for Link Road.

Trunk Roads connected major towns to each other while passing through smaller towns and villages.