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.

Quick Facts M4 motorway, Route information ...

M4 motorway
Mótarbhealach M4
Route information
Length	62 km (39 mi)
Existed	1994–present
History	Completed 1994–2006
Component highways
Major junctions
From	Lucan
Major intersections
To	Kinnegad
Location
Country	Ireland
Primary destinations	Leixlip, Kilcock, Enfield
Highway system
Roads in Ireland Motorways Primary Secondary Regional

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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.^[1]

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. ^[2] The road becomes near-motorway standard dual carriageway again at Collooney, approaching Sligo town.

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.^{[citation needed]}

This section is missing kilometre posts for 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.

More information County, km ...

County	km	mi	Junction	Destinations	Notes
County Dublin
			1	M 50 – Dublin Airport, Dublin Port, Dún Laoghaire	Continues as R148 towards Dublin city centre and Palmerstown.
			2	R 113 ‒ Fonthill, Liffey Valley
			2a	Ballyowen Lane	Westbound exit only. Exit lane runs parallel to mainline, ending at slip road at junction 3.
			3	R 136 – Ballyowen, Lucan
			4	R 120 – Lucan, Adamstown
			4a	L 1018 – Dodsboro, Kew Park	Only Dodsboro is signposted on eastbound approach. Exit lane runs parallel to mainline, ending at slip road at junction 5.
			5	R 148 – Celbridge, Leixlip (westbound)	Heading eastbound, both destinations are followed by the (East) cardinal direction. Continues as M4 motorway.
County Kildare
			6	R 449 ‒ Celbridge (West), Leixlip (West)	Dunboyne
			7	R 406 ‒ Maynooth, Naas	Straffan
			8	R 148 ‒ Kilcock R 407 – Clane	Enfield, Trim
			M4 Toll
			9	R 402 ‒ Edenderry, Enfield	Toll at westbound entrance and eastbound exit slip roads.
County Kildare			Enfield Service Area
County Meath			10	R 401 ‒ Kinnegad
County Westmeath			11	M 6 ‒ Galway, Athlone	Tullamore (N52)
			12	R 148 ‒ Kinnegad, Galway (M6)	Westbound entrance and eastbound exit only.
			13	L 1025 ‒ Coralstown	LILO junction. Continues as N4 dual carriageway.
			14	R 156 ‒ Killucan, The Downs
				L 5720	LILO junction. Westbound entrance and eastbound exit only.
			15	N 52 ‒ Tullamore, Mullingar (East)
			16	N 52 ‒ Dundalk, Mullingar (Centre)
			17	R 394 ‒ Castlepollard, Mullingar (West)	Mullingar Hospital Continues as N4 regular national road.
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Incomplete access        Tolled       Route transition

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This section needs additional citations for verification. (November 2021)

• 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^[3]
• Edgeworthstown – June 2006
• Dromod, Roosky – December 2007
• Castlebaldwin – August 2021^[6][7]

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.^[8] 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.^[9] The road was opened on 18 October 2021.^[6]

• Roads in Ireland
• Motorways in Ireland
• National secondary road
• Regional road