N4 road (Ireland)

The N4 road is a national primary road in Ireland, running from Dublin to the northwest of Ireland and Sligo town. The M6 to Galway diverges from this route after Kinnegad, while the N5 to Westport diverges at Longford town. Most sections of the N4 that are motorway-standard are designated the M4 motorway.

Road standard
The N4 originates at an intersection with the M50 motorway at Junction 7. This is also Junction 1 of the N/M4. The Liffey Valley Shopping Centre is located at Junction 2. The road has three lanes and a bus lane in each direction between the M50 and Junction 5 which is also the start of the M4 motorway at Leixlip.

The N4 was the only one of the main inter-urban national routes whose dual-carriageway section continued into the city centre; however, the section inside the M50 was re-classified as the R148 in 2012.

Heading west, the PPP motorway section (see below) ends west of Kinnegad, and the motorway terminates 5 km further west; it continues as HQDC and bypasses Mullingar. From the Mullingar bypass to Edgeworthstown, the road is a wide single carriageway with hard shoulders. Between Edgeworthstown and Longford, there is a lower standard single carriageway road. Between Longford and Rooskey single carriageway continues at a higher standard. Dromod and Rooskey were bypassed in late 2007. This section of the road consists of three roundabouts and a Type 2 dual carriageway, i.e.: two lanes in each direction and no hard shoulder. The road resumes as a single carriageway with hard shoulders until it reaches Carrick-on-Shannon, where it becomes a local urban road through five roundabouts, and passing over the River Shannon into County Roscommon. The road becomes a high-quality single carriageway bypass 3 km outside of Boyle town, with periodic alternating overtaking lanes passing Lough Key Forest Park and Ballinafad until it reaches Castlebaldwin. From Castlebaldwin to Collooney the road is a Type 2 dual carriageway. Funding for the expansion of this section was announced in October 2018, and it opened in 2021. The road becomes near-motorway standard dual carriageway again at Collooney, approaching Sligo town.

M4 motorway
The section from Leixlip to the west of Kinnegad is the M4 motorway. The first section of this motorway (Leixlip – Kilcock) was opened on 19 December 1994.

Tolled section of the M4 motorway
Under the Government announcement of the pilot projects on 1 June 1999 this project was to be assessed by the NRA for its suitability to be advanced as a Public-private partnership (PPP). Subsequently, the project was included as one of the projects approved under Tranche II of the PPP Roads programme as announced by the NRA in June 2000. The project involved the construction of 39 km of motorway from Kinnegad to Kilcock and is an extension of the Kilcock-Maynooth-Leixlip motorway on the N4/N6 Sligo/Galway to Dublin route. The motorway bypasses the towns of Enfield and Kinnegad.

The PPP contract was awarded in March 2003 to the EuroLink Consortium (SIAC Construction Ltd and Cintra - Concesiones de Infraestructuras de Transporte S.A.) and allows for them to collect tolls for 30 years from that date.

This tolled section (from Kilcock to Kinnegad) opened on 12 December 2005, almost a year ahead of schedule. It is the second-most expensive toll road in Ireland (after the Dublin Port Tunnel). A toll of €3.40 (as of 2024) for cars is charged at a toll plaza just west of Kilcock and at smaller toll plazas at on and off-ramps at Enfield. Between Enfield and Kinnegad, no further access to the M4 is possible.

Eurolink operates this tolling scheme, the first in Ireland not operated by NTR plc. From 2005 to 2007, Eurolink started to accept several tags issued by other motorways such as M1, M8, eTrip and Dublin Port Tunnel tags. On 14 June 2007 NTR plc joined the Nationwide Electronic Toll Payment System introducing their popular EazyPass tags on the system and allowing all other toll plazas in the country (different from those owned by NTR plc) to accept them, meaning that each toll company's electronic tag will work on all toll roads in the State.

In the 1 July 2006 edition of the Meath Chronicle it was claimed that up to 10% of the €420 million road project had "to be ripped up and replaced" shortly after it opened due to rushed construction, however this cost would have had to be carried by the toll operators, not the state, as per the contract.

The bypassed former N4 road has been reclassified as the R148.

Motorway reclassification
On 28 August 2009, the Department of Transport implemented the second round of proposed reclassifications of dual carriageways as motorways under the Roads Act 2007. A short section of the N4 between Kinnegad (J12) and McNead's Bridge (J13) was affected by this. This extended the M4 westward by 6.8 km.

Junctions
The route begins as a dual carriageway at junction 7 of the M50, becoming a motorway after junction 5. It then becomes a dual carriageway after junction 13. After Mullingar, it becomes a regular national road.

{| class="plainrowheaders wikitable" !scope=col|County !scope=col|km !scope=col|mi !scope=col|Junction !scope=col|Destinations !scope=col|Notes Continues as M4 motorway. – Clane Continues as N4 regular national road.
 * rowspan="8"|County Dublin
 * 1
 * – Dublin Airport, Dublin Port, Dún Laoghaire
 * Continues as R148 towards Dublin city centre and Palmerstown.
 * 2
 * ‒ Fonthill, Liffey Valley
 * bgcolor="ffdddd"|2a
 * bgcolor="ffdddd"|Ballyowen Lane
 * bgcolor="ffdddd"|Westbound exit only. Exit lane runs parallel to mainline, ending at slip road at junction 3.
 * 3
 * – Ballyowen, Lucan
 * 4
 * – Lucan, Adamstown
 * 4a
 * – Dodsboro, Kew Park
 * Only Dodsboro is signposted on eastbound approach. Exit lane runs parallel to mainline, ending at slip road at junction 5.
 * bgcolor="dff9f9"|5
 * bgcolor="dff9f9"| – Celbridge, Leixlip (westbound)
 * bgcolor="dff9f9"|Heading eastbound, both destinations are followed by the (East) cardinal direction.
 * bgcolor="ffdddd"|Westbound exit only. Exit lane runs parallel to mainline, ending at slip road at junction 3.
 * 3
 * – Ballyowen, Lucan
 * 4
 * – Lucan, Adamstown
 * 4a
 * – Dodsboro, Kew Park
 * Only Dodsboro is signposted on eastbound approach. Exit lane runs parallel to mainline, ending at slip road at junction 5.
 * bgcolor="dff9f9"|5
 * bgcolor="dff9f9"| – Celbridge, Leixlip (westbound)
 * bgcolor="dff9f9"|Heading eastbound, both destinations are followed by the (East) cardinal direction.
 * – Lucan, Adamstown
 * 4a
 * – Dodsboro, Kew Park
 * Only Dodsboro is signposted on eastbound approach. Exit lane runs parallel to mainline, ending at slip road at junction 5.
 * bgcolor="dff9f9"|5
 * bgcolor="dff9f9"| – Celbridge, Leixlip (westbound)
 * bgcolor="dff9f9"|Heading eastbound, both destinations are followed by the (East) cardinal direction.
 * Only Dodsboro is signposted on eastbound approach. Exit lane runs parallel to mainline, ending at slip road at junction 5.
 * bgcolor="dff9f9"|5
 * bgcolor="dff9f9"| – Celbridge, Leixlip (westbound)
 * bgcolor="dff9f9"|Heading eastbound, both destinations are followed by the (East) cardinal direction.
 * bgcolor="dff9f9"|5
 * bgcolor="dff9f9"| – Celbridge, Leixlip (westbound)
 * bgcolor="dff9f9"|Heading eastbound, both destinations are followed by the (East) cardinal direction.
 * rowspan="6"|County Kildare
 * 6
 * ‒ Celbridge (West), Leixlip (West)
 * Dunboyne
 * 7
 * ‒ Maynooth, Naas
 * Straffan
 * 8
 * ‒ Kilcock
 * 7
 * ‒ Maynooth, Naas
 * Straffan
 * 8
 * ‒ Kilcock
 * 8
 * ‒ Kilcock
 * 8
 * ‒ Kilcock
 * ‒ Kilcock
 * Enfield, Trim
 * bgcolor="dcdcfe" colspan="3" align="center"|IE road sign symbol F-060.svg M4 Toll
 * 9
 * ‒ Edenderry, Enfield
 * Toll at westbound entrance and eastbound exit slip roads.
 * County Kildare
 * colspan="3" align="center"|Motorway Services Ireland.png Enfield Service Area
 * County Meath
 * 10
 * ‒ Kinnegad
 * rowspan="8"|County Westmeath
 * 11
 * ‒ Galway, Athlone
 * Tullamore (N52)
 * bgcolor="ffdddd"|12
 * bgcolor="ffdddd"| ‒ Kinnegad, Galway (M6)
 * bgcolor="ffdddd"|Westbound entrance and eastbound exit only.
 * bgcolor="dff9f9"|13
 * bgcolor="dff9f9"| ‒ Coralstown
 * bgcolor="dff9f9"|LILO junction. Continues as N4 dual carriageway.
 * 14
 * ‒ Killucan, The Downs
 * bgcolor="ffdddd"|
 * bgcolor="ffdddd"|
 * bgcolor="ffdddd"|LILO junction. Westbound entrance and eastbound exit only.
 * 15
 * ‒ Tullamore, Mullingar (East)
 * 16
 * ‒ Dundalk, Mullingar (Centre)
 * 17
 * ‒ Castlepollard, Mullingar (West)
 * Mullingar Hospital
 * bgcolor="ffdddd"|12
 * bgcolor="ffdddd"| ‒ Kinnegad, Galway (M6)
 * bgcolor="ffdddd"|Westbound entrance and eastbound exit only.
 * bgcolor="dff9f9"|13
 * bgcolor="dff9f9"| ‒ Coralstown
 * bgcolor="dff9f9"|LILO junction. Continues as N4 dual carriageway.
 * 14
 * ‒ Killucan, The Downs
 * bgcolor="ffdddd"|
 * bgcolor="ffdddd"|
 * bgcolor="ffdddd"|LILO junction. Westbound entrance and eastbound exit only.
 * 15
 * ‒ Tullamore, Mullingar (East)
 * 16
 * ‒ Dundalk, Mullingar (Centre)
 * 17
 * ‒ Castlepollard, Mullingar (West)
 * Mullingar Hospital
 * bgcolor="ffdddd"|
 * bgcolor="ffdddd"|
 * bgcolor="ffdddd"|LILO junction. Westbound entrance and eastbound exit only.
 * 15
 * ‒ Tullamore, Mullingar (East)
 * 16
 * ‒ Dundalk, Mullingar (Centre)
 * 17
 * ‒ Castlepollard, Mullingar (West)
 * Mullingar Hospital
 * 16
 * ‒ Dundalk, Mullingar (Centre)
 * 17
 * ‒ Castlepollard, Mullingar (West)
 * Mullingar Hospital
 * 17
 * ‒ Castlepollard, Mullingar (West)
 * Mullingar Hospital
 * 17
 * ‒ Castlepollard, Mullingar (West)
 * Mullingar Hospital
 * Mullingar Hospital

Bypasses



 * Palmerstown – 1984
 * Lucan – 1988
 * Leixlip, Maynooth, Kilcock – 1994
 * Mullingar – 1994
 * Longford – 1995
 * Drumsna, Jamestown – 1997
 * Collooney, Ballisodare – January 1998
 * Boyle, Ballinafad – 1998–1999
 * Sligo (partial) – September 2005
 * Enfield, Kinnegad – December 2005
 * Edgeworthstown – June 2006
 * Dromod, Roosky – December 2007
 * Castlebaldwin – August 2021

Upgrades


In July 2009, an upgrade of the section between the M50 junction and the Leixlip interchange was completed. In this section the road is three lanes in each direction, the median crossings were removed and the junction with the R120 is a fully grade-separated junction. Private accesses and some left turns remain which prevents the section from being designated a motorway. The speed limit is 80 km/h. There are currently no signal-controlled junctions on the N/M4 between the M50 motorway and the Sligo through-pass.

In 2013, a 5 km stretch of dual carriageway with at-grade crossover junctions between the M4 and the Mullingar bypass was upgraded to HQDC.

Construction of a 2+2 road at the 15 km stretch between Collooney and Castlebaldwin began in 2019 to improve road safety. The road was opened on 18 October 2021.

Planned improvements to the route

 * Mullingar to Longford; 40 km dual carriageway, including bypass of Longford Town. As of November 2023, route corridor options have been presented, awaiting decision on preferred route corridor.
 * Dromod to Carrick-on-Shannon 21 km, including 10 km bypass of Carrick-on-Shannon. At planning stage, as of November 2023.