M7/N24 Ballysimon Junction Improvement Scheme

Project Summary

The existing motorway bridge originally accommodated a total of 3 traffic lanes (two straight through lanes and one turning lane). The improvement works increased this provision to 5 lanes (four straight through and one turning lane) by removing the hard shoulder and reducing the existing raised verge width.

Project Description

This road realignment scheme provided junction capacity improvement works and also, a new roundabout, some realignment and new drainage on the N24 Trunk Road over a length of 2.0km.  The motorway junction consisted of a dual carriageway bridge over the M7 Motorway with the on and off slip lanes forming staggered junctions with the N24 which were controlled by traffic signals.  The scheme included widening of the northbound M7 slip road to provide an additional lane for exiting traffic.

Project Delivery

Realignment works on the N24 included construction of a new roundabout at its junction with the Old Ballysimon Road. The works also included construction of new drainage systems and installation of services ducts over a length of 2km, new road formation, diversion of a stream into a new precast concrete box culvert, a gabion basket embankment, street lighting, protection of live services, carriageway surfacing and re-surfacing, line marking, fencing and landscaping.  Waterproofing remedial works to the existing bridge structure were instructed during the works.  The two sets of traffic signals on the bridge were replaced as part of the works and the traffic signal control system was upgraded to improve coordination between the two sets of signals.

There was approximately 14,000m2 of road construction on the project. The construction type varied from full road construction to partial road construction to re-surfacing depending on the change in levels/alignment proposed or if it was a new section of pavement.  Coffey Construction undertook the earthworks to formation level and the sub-base, base course, binder course and surface course were sub-contracted to Roadstone Wood Ltd (RWL).  Regular liaison took place with RWL to ensure the timely sequencing of operations as well for quality control.  Tarmac planings were recycled to reduce the carbon footprint of the project and some existing safety barriers, lighting columns and bridge deck drainage units were re-used, providing a saving to the client.

Traffic Management (TM) formed a large part of the works as the works site was on an existing busy interchange.  All TM Plans were approved by the local authority and the police prior to implementation.  Once implemented, TM systems were inspected twice each day.

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