Ireland - Services


Bridges & Tunnels

RPS has a proven track record in delivering optimum, efficient and elegant bridge solutions. Our bridge forms include concrete and steel solutions for crossings of road, river, rail and coastal bays, as well as complex interchanges incorporating bridges and tunnels. Our bridge design philosophy is to design for appearance through the life of the structure with minimum recourse to maintenance. We also deliver engineering services for existing bridge structures of various forms and materials, including inspections, assessments and rehabilitation works.

We are experienced in the conceptual and detailed design of cut and cover tunnels, top down tunnels, immersed tunnels, bored tunnels and hard rock tunnels. Recent examples of large tunnel developments include Limerick Tunnel under the Shannon Estuary and the early development of tunnels for Metro North.

Case Studies

Limerick Tunnel



The 675m tunnel under the River Shannon is one of the largest and most complex infrastructural projects ever undertaken in Mid-West Ireland.

RPS, in a joint venture with COWI A/S of Denmark, fulfilled the role of project consultant and worked with Limerick City & County Council and Transport Infrastructure Ireland to deliver the southern bypass of Limerick City. This key piece of infrastructure forms a critical link from the N18 to the N7, part of the Atlantic Corridor on the west coast of the country.

We developed the project through constraints study, route selection, traffic modelling, tolling studies, preliminary design, EIS, CPO and oral hearing. Once planning permission was granted, we provided technical advice and assistance to Transport Infrastructure Ireland for the tender phase and provided technical advice, design review and contract monitoring services during the construction phase of the project.

The project comprises 10km of mainline dual carriageway, four grade separated junctions, 11 major bridges, including two bridges in excess of 100m in length and the tunnel itself. The two largest bridge structures were the N18 Interchange Underbridge (122m) and St. Nessan’s Road Overbridge, a reinforced earth structure (115m).

The key element of the preliminary design was the selection of a crossing type for the River Shannon with factors including marine traffic, environmental, engineering and cost considerations. The tunnel was ultimately favoured over low or high level bridge options based on long term environmental benefits and significant public support for the tunnel option.

M8/M73/M74 Motorway Improvements, Scotland


Image: courtesy of Lagan Forrovial


RPS acted as Contractor’s Designer on behalf of Transport Scotland for this major £400m DBFO project comprising a new 12km dual three-lane motorway section of the M8 between Bailliestown and Newhouse, with three new grade separated motorway junctions and amendments to two existing motorway junctions. It also comprised upgrades to approximately 16km of the existing motorway network including widening for additional lanes, realignments, drainage, mining stabilisation works, environmental mitigation and provision of Intelligent Transport System (ITS) across the network.

RPS carried out the detailed design for 40 structures on the project; of which 23 were new structures and 13 existing bridges were widened and/or strengthened. The project also involved traffic signals, lighting, drainage, pavement, road markings, footways and cycleways, road markings, soft ground challenges (including deep peat), environmental management, gantries, noise barriers and demolition of existing structures.

Raith Interchange was the most complex element of the scheme involving the construction of a new underpass structure to provide free flow for the existing A725, the realigned Raith Roundabout, three new bridge decks, pedestrian and cyclist facilities over the roundabout and flood alleviation storage ponds. RPS delivered a combined temporary and permanent works solution for the junction. The detailed design for the underpass at Raith, approximately 600m long, included a secant pile wall solution with inclined ground anchors at the head. The anchored solution optimised secant pile diameters and toe depths and controlled lateral wall deflections while increasing durability performance.

RPS developed a BIM model of the interchange, a collaborative effort between RPS, contractor and O&M teams. The use of BIM enabled our permanent and temporary works designers to coordinate the design of the permanent works with traffic management, dewatering and temporary works.

This project was awarded an ACEI Design Excellence Award in 2018.

Mulroy Bay Bridge



The Mulroy Bay Bridge project involved the construction of a high level multi-span bridge across Mulroy Bay in Co. Donegal and associated approach roads and pedestrian facilities. The bridge is approximately 320m long, comprising of 5 spans with a main span of 100 metres. The deck is a post tensioned reinforced concrete box girder section, constructed by the balanced cantilever construction method. The bridge spans onto reinforced concrete piers and reinforced concrete and reinforced earth abutments. The piers are founded on pilecaps over water. The approach roads are approximately 2.6 km in length, comprised of a two lane single carriageway with 3.5m lane widths and footpaths each side.

RPS worked on Mulroy Bay Bridge from its inception, undertaking the feasibility study, preliminary and detailed design work, and environmental impact statement. Our team delivered the project through planning and then supervised the construction of the bridge.

The crossing was successfully delivered in a Special Area of Conservation and a Natural Habitat Area. The height of the bridge had to allow for continued use of the estuary by commercial fishing vessels. Close liaison between the environmental and engineering design teams ensured mitigation of environmental impacts was incorporated within the design. Extensive public consultation with local residents and commercial operators was undertaken throughout the development.