Projects - N4 Lucan Bypass

N4 Lucan Bypass

Project Description

The contract comprised of the design and execution of the widening of the existing road (5.9km) from 2 lane dual carriageway with hard shoulder to 3 lane carriageway with bus lanes. It included a section of split-level carriageway, conversion of the at-grade signalled Newcastle Road Junction to a grade separated junction which included an overbridge and 4 ramps, provision of signal controls on the at grade junctions between the slip road and the realigned Newcastle Road. There were 18 no principle structures on the project which included the replacement of 2 no. footbridges. There was also strengthening works carried out to another footbridge and remedial works carried out to the existing structures.

There was extensive Traffic Management on this project as this is a main artery from Dublin (AADT 75,000). It included a temporary diversion which consisted of a temporary signalised gyratory on the N4 dual carriageway at its junction with the Newcastle Road to allow for the construction of the Newcastle Road Bridge.

There was a substantial rock cut at Newcastle Junction, which was reprocessed and utilised throughout the project. The contract also included substantial diversion of services in very tight areas including Bord Gais, ESB, NTL, Eircom and South Dublin Watermain and Sewer division.

Through liaison with the Parks Department the design of the attenuation pond changed to a fully constructed wet land feature.


South Dublin County Council


Lucan, County Dublin


Roughan and O Donovan


JB Barry Partners


Works Contractor, Designer, PSCS and PSDP