New road development strengthens transport connectivity in the south-east of Ireland

Creating an enhanced user experience

Procured as a public-private partnership (PPP), the N25 New Ross bypass provides a quality transportation route, improving regional, national, and international connectivity on the N25 Cork to Rosslare Euroroute. It also links the N25 with the N30 New Ross to Enniscorthy route.

Arup took a user-led design approach to enhance the experience of road users. Our design aimed to improve road efficiency and safety and to optimize trip predictability and connectivity. Our engineers designed numerous features along the 8.7km of N25 divided highway, 5km of N30 divided highway, and 1.2km of N30 tie-in undivided highway, including one interchange, three at-grade intersections, an overpass crossing the abandoned New Ross/Waterford railway line, 11 local road bridges, and 13 minor structures.

Rose Fitzgerald Kennedy Bridge: Ireland’s longest bridge

At 887m in length, the new bridge—the 46th crossing over the River Barrow—is the longest river crossing in Ireland, connecting Pink Point in Kilkenny to Stokestown in Wexford. At 36m above the Barrow, there is ample space for shipping traffic to pass under the bridge into the Port of New Ross. Before the design of this project, the O’Hanrahan Bridge was the only crossing in New Ross and was plagued with delays and frequent closures.

This three-tower extradosed bridge combines the main elements of both a prestressed box girder bridge and a cable-stayed bridge.

An extradosed bridge uses much shorter towers than a cable-stayed bridge and a significantly shallower deck than a box girder, resulting in a bridge that harmonizes with its surroundings while providing the necessary navigational clearance into the Port of New Ross.

Arup and CFC designed the bridge to consist of nine spans in total. The cross-section of the deck is a single box of prestressed concrete with inclined precast solid panels to reduce the cantilever length while providing a smooth appearance. Due to the high compressive forces associated with long-span extradosed bridges, high-strength concrete up to C80/95 was necessary for large parts of the deck box.

The scale of the structure is impressive in its size and slenderness, rising 36m over the water. The central 650m of the crossing over the river and floodplain is spanned with only three supports, using a single plane of stay cables to support the deck, each of them having up to 125 strands. The cables went through a full scale of two million cycles of fatigue testing in a lab in Chicago, one of only two labs worldwide that can test cables of this size.

Constructing the longest bridge in Ireland required significant temporary structures, including two temporary piers, a push-pull prop for the balanced cantilever construction, and a temporary artificial island to facilitate the construction of the main central pier. Reviewing the design of the temporary structures was a key part of our role in coordinating safety and health during the design process.

Protecting the surrounding area: designing for conservation

Arup’s flooding team conducted 2D hydrodynamic modeling to estimate the potential changes in the flow regime associated with both the temporary island and the permanent in-channel bridge pier. A detailed scour assessment was also conducted to estimate the likely scour depths and extents related to the bridge pier.

Arup’s environmental consultants advised on the design of the project to ensure that it is compatible with its surroundings. The River Barrow is a candidate Special Area of Conservation (cSAC), due to rare habitats and species, and the River Barrow Estuary is a proposed Natural Heritage Area.