Motorways in Ireland

In Ireland, the highest category of road is a motorway (mótarbhealach, plural: mótarbhealaí), indicated by the prefix M followed by one, two or three digits. The Motorway network predominantly consists of two-lane dual carriageways primarily focused around Dublin, although a few motorways contain three lanes and the M50 has four lanes at some points.

The completion of the Major Inter-Urban motorway project in December 2010, which connected Dublin completely by motorway to the cities of Cork, Limerick, Waterford and Galway, as well as other projects, increased the total motorway network in the state to 916 kilometres (569 mi). Planned new road construction will possibly lead to almost 1,100 kilometres (680 mi) of motorway by 2035, subjected to availability of funding.

Motorways in Ireland have a set of restrictions, which prohibit certain traffic from using the road. The following classes of traffic are not allowed on Irish motorways:

Rules for driving on motorways include the following:

The general motorway speed limit is 120 km/h (75 mph).

For more on motorway specification in general, view this motorway article.

Motorways in Ireland are generally constructed to high-quality dual carriageway standard – with sightlines, curves and elevation designed for 120 km/h speeds. Until recently, all motorways were built with wide medians in the centre, which typically have a wire or steel barrier. The more recent schemes have narrow medians, only 3 metres in width, with a concrete barrier in the middle. These narrow-median schemes also have reduced carriageway width – a typical narrow-median motorway cross section has two 3.5-metre running lanes, a 2.5-metre hard shoulder and a 1.5-metre central reserve in each direction whereas a typical wide median motorway has 3.75-metre running lanes and a 3-metre hard shoulder. Ireland has only a small amount of D3M (motorway with three lanes in each direction). The M50 is the most notable example, having been upgraded in parts from a two-lane motorway, to a three or four lane motorway in each direction.

Apart from terminal junctions, motorways can only be accessed using grade-separated junctions. These typically take the form of roundabout interchanges for higher-capacity junctions, or dumbbell interchanges – which are a variant on the diamond-style interchange. – for lower-trafficked interchanges. A number of other types of junction are also used on the motorway network. The M4/M6 and M7/M9 junctions use a variant of the trumpet-style interchange while the M50/N7 and M50/N4 interchanges use partial cloverleaf junctions.

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Wikipedia