High-quality dual carriageway

A High-quality dual carriageway (HQDC) is a category of road in Ireland. It is an all-purpose dual carriageway road type built to near motorway standards, but without motorway classification or motorway restrictions. High-quality dual carriageways have full grade-separated access and do not have junctions with minor roads. Such roads in the Republic of Ireland have been built as part of the 2000-2006 and 2007-2013 National Development Plans, including interurban routes from Dublin to other cities.

While HQDCs or roads of similar type exist in a number of countries this article concentrates mainly on such roads in Ireland.

Standard motorways: 52,000 vehicles AADT - annual average daily traffic. The road type is all-purpose dual carriageway (D2AP), but with the same specifications as motorway: a carriageway width of 7 metres (23 ft) and a hard shoulder of 2.5 metres (8 ft 2 in) width. HQDCs are limited access (grade-separated junctions only) and not intended to have junctions with minor roads. Junctions with major roads are grade-separated and to motorway standards.

All HQDCs in Ireland currently form part of national primary roads, and therefore use the national road speed limit of 100 km/h (62 mph). There are exceptions however, as special speed limits may now be specified for sections of road if the local authority passes a by-law. For example, a section of the N1 from the northern end of the M1 motorway (north of Dundalk to the border with Northern Ireland) has a 120 km/h (75 mph) speed limit.

Signage on Irish HQDCs is similar to signage used on Irish motorways, and junction numbers may be present (as on motorways, indicated by a white number on a black panel in the corner of signs). However signage on HQDCs uses a green background instead of the blue background used on Irish motorway signage. In the event of an HQDC being a regional road, black text on a white background would be used instead. Also, as on other all-purpose roads, signs should include patches for roads of other classifications (on motorways, all information signage should have a blue background).

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