National Roads (Republic of Ireland)
National Roads (Bóithre Náisiúnta) constitute the most important category of publicly maintained roads in the Republic of Ireland. Bearing one- or two-digit numbers in the series N1–N50 (National Primary Roads) and N51–N99 (National Secondary Roads), they are – as the name implies – roads of national strategic importance. Their planning, development, management, and maintenance are the responsibility of Transport Infrastructure Ireland: the operating name of the National Roads Authority, an agency of the Irish state established in 1994.
All or part of the length of any national road may be declared by the Minister for Transport to meet the requirements necessary for classification as a motorway: in such cases the N prefix of the road number is changed to M. It is important to be aware that in the Republic of Ireland motorways remain national roads: thus the M20, for example, is a part of the N20.
National roads are waymarked in white-on-green (with route numbers shown in gold), except where they have been classified as motorways, in which case the background colour of directional signs is blue and the route numbers are shown in white.
National roads are, in general, the only roads to have a speed limit higher than 80 km/h.
National Primary and National Secondary Roads
The distinction between national primary and national secondary roads is principally a planning and administrative one. The Department of Transport's Traffic Signs Manual describes national primary roads (including those classified as motorways) as "generally the major long-distance through routes linking principal cities, large towns, ports, and airports. They serve major geographical regions and a high percentage of the total population". It describes national secondary roads as "generally medium-distance through routes serving medium to large geographical areas".
For the ordinary road user there is no distinction between the two classes of national road, whether in terms of directional signage or in the regulations applied, such as the default speed limits, which in the absence of local restrictions are 100 km/h (or 120 km/h on motorways).
NB: This article is in the course of construction.