N4 Collooney to Castlebaldwin

Sligo’s Largest Infrastructural Project In Modern Times

Official Road Opening

An Taoiseach Micheál Martin, T.D. officially open the new N4 Collooney to Castlebaldwin Roads Project in County Sligo on Monday 18th October 2021.

An Taoiseach, Micheál Martin, T.D. said

“This project is about enhancing people’s quality of life.  It will significantly improve road safety for local communities and for everyone travelling between Sligo and Dublin.  The new road will also be a catalyst for sustainable regional growth and development, encouraging further investment and employment opportunities in Sligo and the Northwest.  It will enhance the quality of life of this community, improving accessibility and making this an even more attractive destination for investment and a place to work and live.”

Minister of State at the Department of Transport, Hildegarde Naughton, T.D. said

“The opening of the N4 today is not only an important milestone for Sligo, the communities and businesses that it serves; so too is it critical from a road safety perspective.  Tragically, in the past three decades we have lost 30 lives on the old N4; I am confident that the 15km of new National Primary Road will make it a safer place for commutes to work and school, or for travel to visit friends and family in the decades ahead.  While it is impossible to put a price on any one life saved on our roads, Government’s investment of €140 million on this vital piece of infrastructure will result in 27 fewer fatalities and 87 fewer serious injuries by 2051, based on current predictions.”

Welcoming the project Councillor Paul Taylor, Cathaoirleach of Sligo County Council said

“This is an important project for everybody in Co. Sligo.  Removing cars and trucks from the old N4 and designating it a Local Road with a new cycleway makes local communities safer and enables people to choose walking or cycling for short local journeys.  It also has the potential to be a game changer by helping to boost the local economy, bring jobs to the region and make Sligo a better and safer place to live, travel, and work in.”

The N4 National Primary Route is part of the East/West road corridor linking Ireland’s largest transportation node (Dublin) with the largest transportation node in the North West (Sligo).  It measures c. 34.8km in County Sligo of which c. 11.6km between Sligo Town and Collooney is Type 1 Dual Carriageway with c. 8.8km south of Castlebaldwin having already been realigned to Standard Single Carriageway standard (Part of the N4 Curlews Bypass).

The new N4 Type 2 Dual Carriageway between Collooney and Castlebaldwin is one of the most significant road projects ever built in the Northwest Region. It provides approximately 15km of new national road, built to the highest safety, environmental and infrastructural standards, and will change the future of Sligo. It forms part of a key strategic link between Dublin and Sligo and also opens up the N17 Atlantic Economic Corridor network. It has the potential to be a game changer – by helping to boost the local economy, bring jobs to the region and make Sligo a better and safer place to live, travel, and work.

The N4 Collooney to Castlebaldwin Road Project links the existing N4 Dual Carriageway at Collooney to the Curlews By-Pass, just south of Castlebaldwin village. It completes the upgrade of the N4 to modern standards in County Sligo. Included in the Scheme is 8km of new and upgraded side roads, 12 Primary Bridge Structures and 3km of off-road cycleway.

Delivery of this Scheme is projected to:

  • Significantly improve safety, by reducing the number of fatalities and injuries on the N4 and the existing surrounding local road network.
  • Reduce inter-urban journey times and improve journey time reliability, which will remove barriers to economic development of the region.
  • Provide a corridor of transport infrastructure that will encourage and support existing investment and employment in Sligo and the North West.
  • Improve Road based Public Transport, quality of life for residents and improve accessibility to work, education and other activities.
  • Improve conditions for pedestrians and cyclists wishing to access local services.

National Policy Context

The N4 Collooney to Castlebaldwin Road Scheme was included in the Building on Recovery: Infrastructure and Capital Investment Capital Plan 2016-2021, as a key priority in the roads programme which will support economic growth. The Plan identified it as one of the “critical gaps” in our existing infrastructure, which needs to be upgraded.

A core priority under Project Ireland 2040 National Planning Framework is the essential requirement to enhance and upgrade accessibility between urban centres of population and their regions, in parallel with the initiation of compact growth of urban centres. This has a crucial role to play in maximising the growth potential of the regional urban centres, one of which is Sligo, and the economy. The delivery of the N4 Collooney to Castlebaldwin Scheme is listed as one of the key Schemes to be delivered under Strategic Outcome No. 2 ‘Enhanced Regional Accessibility’ of the National Development Plan

This Road Development Project comprises of the following:

  • 2.7km of upgrading the existing single carriageway to a Type 2 Dual Carriageway from the N4/N17 Toberbride Roundabout to Doorly Td.
  • 11.2km of offline Type 2 Dual Carriageway between Doorly Td. and the proposed Castlebaldwin Roundabout junction which is just to the southeast of Castlebaldwin village.
  • 0.80km of offline Type 1 Single Carriageway to tie in with the existing N4 at the end of the Curlews Bypass.
  • 4.5km of Type 3 Single Carriageway which run parallel to the mainline on the online section between the N4/N17 Toberbride Roundabout and Doorly Td.
  • 8.0km of side roads to facilitate construction of bridge structures and their approaches across the mainline.
  • One roundabout on the mainline together with the upgrade of the N4/N17 Toberbride Roundabout.
  • Four roundabouts on the local road network.
  • One Compact Grade Separated junction at Drumfin / Cloonlug Td. serving Ballymote, Riverstown and the local hinterlands.
  • 3.4km of combined footway/cycleway from the N4/N17 Toberbride Roundabout in Toberbride Td. to Doorly Td. just north of the N4/L-1302 junction.
  • 0.7km of combined footway linking the Miners Way in Annaghcor Td. to Castlebaldwin Village.
  • Ancillary works including retaining walls, the provision of drainage and attenuation systems, spill containment, petrol interceptors, various utility diversion and extension works, earthworks, pavement construction, boundary treatment, landscaping and street lighting.

The first 2.7km of the development at the Collooney end is online and consists of an upgrade of the existing N4 Single Carriageway to a Type 2 Dual Carriageway. It then veers offline, to the west of the existing N4 National Primary Road for approximately 7.62km where it crosses the existing N4 at Ardloy Td. (Ch10,200 approximately) to the east side and continues in a southerly direction to the east of Castlebaldwin Village in Castlebaldwin Td. where a roundabout shall be constructed. (Castlebaldwin Junction). A Type 1 Single Carriageway, which will be commensurate with the existing improved section to the south known as the Curlew Mountain Bypass, shall be constructed from Castlebaldwin Junction in a southerly direction to the tie-in location with the existing N4 National Primary Road in the townland of Cloghoge Lower Td., a total length of approximately 0.8km

View looking southeast towards Structure 2 under construction in Doorly Td.

View looking northwest at Structure 1 in Toberbride Td.

To provide connectivity with the local road network, dwellings, and farm accesses along the eastern side of the online upgrade section, a single carriageway parallel access road (Eastern Parallel Link) has been constructed between Toberbride Td. and Doorly Td. This access road connects to the eastern arm of the N4/N17 Toberbride Roundabout and the existing N4 at Doorly Td. just to the north of the local road (L1302-0) junction with the existing N4 and is currently being used to serve the National Road traffic while the existing N4 along this section is being upgraded to a Type 2 Dual Carriageway.

To provide connectivity with the local road network, dwellings, and farm accesses along the western side of the online upgrade section, a single carriageway parallel access road (Western Parallel Link) is constructed to the west of the existing N4 between Cloonamahan Td. and Doorly Td. This proposed access road shall be linked to the eastern parallel road via a proposed underbridge at Doorly Td.

An overbridge is being constructed at Toberbride Td. from the proposed Eastern Parallel Link Road to facilitate connectivity of existing local road network in this area. An underbridge is being constructed at Doorly Td. to connect the Eastern Parallel Link road and the Western Parallel Road.

Aerial view looking northwest of Castlebaldwin Roundabout and approach roads

Aerial view looking towards newly constructed Castlebaldwin Roundabout

The N4 Collooney to Castlebaldwin Road Project has a dedicated website n4realignment.ie where you will find the following:

  • Contacts for the construction project.
  • Project construction updates and newsletters.
  • Traffic management updates, etc.

Roadbridge Ltd. was awarded the construction contract and commenced the detailed design and construction works in Quarter 1, 2019. The project required significant earthworks. Poor ground conditions proved a major challenge through the construction of the road embankments with peat depths ranging from 2 – 8m. A haul road was constructed along one side of the embankment with the unsuitable material cast to the side and relocated to permanent storage areas once the haul road was complete.

Current Progress

Works were substantially completed in Q3, 2021 and the new Type 2 Dual Carriageway was opened under traffic management to traffic on the 23rd August 2021. The new road was officially opened to traffic on Monday the 18th October 2021 by An Taoiseach Micheál Martin. Some outstanding snagging and accommodation works were completed over the remaining months in 2021.


The Project requires the construction of four overbridges, six under bridges and two clear span river bridges across the Drumfin and Turnalaydan rivers as setout in Table below. Snagging works are currently being undertaken on nine of the structures with deck construction nearing completion on the remaining three.

Structure Number Structure Name
Structure 1 Toberbride Overbridge
Structure 2 Doorly Underbridge (North)
Structure 3 Doorly Underbridge (South)
Structure 4 Lackagh Bridge
Structure 5 Turnalaydan River Bridge
Structure 6 Drumfin Overbridge (North)
Structure 7 Drumfin Overbridge (South)
Structure 8 Drumfin Riverbridge
Structure 9 Carrownagark underbridge
Structure 10 Kingsbrook Underbridge
Structure 11 Existing N4 Ardloy Underbridge
Structure 12 Tawnagh Underbridge

Aerial view looking north east of the L-5502 following opening under traffic management to traffic in September 2020

Aerial view looking north of the Compact Grade separated junction at Drumfin / Cloonlurg Td. on the L-1502 under construction

View looking northwest at Structure 8 Drumfin River Br. in Carrowkeel/Cloonlurg Td’s

View looking north at Structure 1 in Toberbride Td.


The Project also requires the construction of approximately 50 culverts to facilitate connectivity of existing streams and drainage networks. These culverts were designed and constructed in consultation with the OPW and IFI, considering all requirements of these Statutory Bodies. Works on culverts is now largely complete.

Aerial view looking northeast of Culvert under construction at Toberscanavan Td. which serves the outlet channel of Toberscanavan Lough

View looking northeast of a culvert under construction in Cloghoge Lower Td. to facilitate a landowner accommodation road (Stream Riverbed mitigation evident)

View looking northeast of a culvert under construction in Cloghoge Lower Td. to facilitate a landowner accommodation road (Stream Riverbed mitigation evident)

Combined Footway/Cycleway

The Project includes construction of 3.4km of combined footway/cycleway from Toberbride Td. in Collooney to Doorly Td. During the detailed design stage, its location was redesigned offline to provide a facility which more replicates a greenway and which shall provide a safer environment with increased amenity value. Construction of this greenway is now complete with only snagging works outstanding.

View looking southeast in the townlands of Ardcurley and Cloonamahan where the offline Greenway facility can be seen on the left of the image

The planning and design of the N4 Collooney to Castlebaldwin Road Project was developed in accordance with the National Roads Authority (Now Transport Infrastructure Ireland) Project Management Guidelines. This document outlines the framework for the phased approach to the development, management and delivery of national road schemes. The 2010 version which applied largely to this Project set outs the progression of a National Road Realignment Project into seven phases as outlined below:

Following An Bord Pleanála’s confirmation of the Environmental Impact Statement (EIS) and Compulsory Purchase Order (CPO), Sligo County Councils National Road Project Office continued to manage the development of the Project.

The Notice to Treat and Notice to Enter were issued to affected landowners in Q1, 2015 to enable Advance Works Contracts to commence.  The following Advance Works Contracts were prepared, tendered and managed directly by Sligo County Council (SCC) National Road Project Office (NRPO) and completed from 2015 to 2017:

  • Archaeological investigation and preservation by record.
  • Ground Investigation.
  • Service Diversions which included 110kv diversion works and construction of a 220kv pylon.
  • Detailed topographical survey.
  • Topographical Check Survey.
  • Building demolition.
  • Fencing and tree clearance.

View Advanced Works Photos on the Sligo County Council website 

This also enabled land purchase to commence. The Project required the compulsory acquisition of approximately 450 acres of land which impacted 135 landowners and 16 house owners. All house cases have been closed out with only four land acquisition cases remaining. Sligo County Council wishes to take this opportunity to acknowledge the goodwill and co-operation of the affected landowners throughout the progression of this Project.

A tender process was undertaken to appoint Consultants to progress remaining Phases 5 works in addition to provision of technical support to Sligo County Council for Phase 6 and 7 of the NRA Project Management Guidelines. Halcrow Barry (Now Barry Transportation Ltd.) were awarded this Contract in Q2, 2017.

A Contract Notice for the main construction works was published on e-Tenders and the associated Official Journal of the European Union (OJEU) website commencing the pre-qualification process for a construction contractor in Q4, 2017. Seven Candidates submitted Suitability Assessment Questionnaires by the closing date in Q1, 2018. Following assessment, five Candidates were shortlisted and invited to tender in Q2, 2018. Tenders were received from four of the five Candidates before the deadline for tender receipt in Q3, 2018. The fifth Candidate withdrew from the tender process in May 2018. A detailed tender assessment was undertaken to determine the winning Candidate.

Sligo County Council sought the necessary approvals to award the contract in Q4, 2018. Approval was granted to award the construction contract to Roadbridge Ltd. in January 2019.

In early December 2013, correspondence was received from the NRA (now TII) conveying approval to publish the Compulsory Purchase Order (CPO), Environmental Impact Statement (EIS) and Natura Impact Statement (NIS) and to submit the N4 Collooney to Castlebaldwin Proposed Road Development to An Bord Pleanála for planning approval.  The publication of Statutory Notices in Local and National press on the 19th and 21st December 2013 commenced this process.  The CPO, EIS and NIS were placed on Public display and submissions or observations were requested to be made by interested parties to An Bord Pleanála.

The Board subsequently held an Oral Hearing from the 28th to the 30th of April in the Castledargan Hotel, Ballygawley.  This provided a forum for the cross examination of the aforementioned witnesses by those who had made bona-fide submissions and the Inspector delegated by the Board to conduct the hearing.

Following this the Board, having considered the objections made and the report of the Inspector who conducted the Oral Hearing approved (on the 22nd of July, 2014) the Proposed Road Development under section 51 of the Roads Act, 1993 (as amended).  The Board also confirmed the CPO for the Proposed Road Development.  Notice of Confirmation of the CPO was published in the Sligo Weekender on the 28th August 2014 with the CPO becoming operative 3 weeks later.  The eight week period during which an appeal to the High Court could take place ended on the 24th October, 2014.

View Environmental Impact Statement for the Proposed Road Development

View Briefs of Evidence for the Proposed Road Development 

View An Bord Pleanála for the Proposed Road Development Oral Hearing 

View Supplementary Information for the Proposed Road Development Oral Hearing

The scheme was designed in-house by Sligo County Council’s National Road Project Office Team so the lead witnesses at the An Bord Pleanála Oral Hearing were Sligo County Council Road Design Engineers.

The Environmental Impact Statement (EIS) was also produced by the Sligo County Council’s National Road Project Office Team whom also coordinated and managed the environmental assessment input from groups of specialist sub-consultants whose disciplines related to Traffic Modelling, Geotechnical, Flood Risk, Socio-Economic, Non-Agricultural Property, Noise and Vibration, Air Quality, Landscape and Visual, Agricultural Property, Flora, Fauna and Fisheries, Soils and Geology, Hydrology and Hydrogeology, Archaeology, Architecture and Cultural Heritage.  Each sub-consultant also provided evidence at the Oral Hearing relative to their various disciplines.

The detailed and complex Compulsory Purchase Order (CPO) was also prepared by members of the in-house National Road Project Office team.


Current Status

  • An Bord Pleanála approved the Project in July 2014.
  • The Compulsory Purchase Order was confirmed by Sligo County Council in August 2014.
  • All advance works completed between 2015 and 2017.
  • Land purchase and accommodation works agreements 98%
  • Construction contract awarded to Roadbridge Ltd. in January 2019.
  • Construction works completed in October 2021.
  • Official Road Opening by An Taoiseach Micheál Martin, T.D. on the 18th October 2021.

Contact Details

Project Contact Details

Roadbridge Ltd:

Sligo County Council: