M8/M73/M74 Motorway Improvements PPP, Scotland

RPS acted as the contractor’s designer on behalf of Transport Scotland for this major £400m DBFO project comprising a new M8 dual three-lane motorway section between Bailliestown and Newhouse, with three new grade separated motorway junctions and amendments to two existing motorway junctions.

The works also included; multiple new structures, alterations to existing structures, traffic signals, lighting, drainage, pavement, road markings, footways and cycleways, road markings, soft ground challenges (including deep peat), pavements, environmental management, gantries, noise barriers and demolition of existing structures.

RPS carried out the detailed design for 16km of existing motorway network including widening for additional lanes, realignments, drainage, mining stabilisation works, environmental mitigation, new and re-configured roundabouts, 40 structures of which 23 were new structures (underpasses, highway bridges, rail bridges, foot/cycle bridges, culverts and retaining) and provision of Intelligent Transport System (ITS) across the network.

Raith Junction is 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.

RPS developed a BIM model of the Interchange, a collaborative effort between RPS, Contractor and O&M teams. The use of BIM has enabled our permanent and temporary designer to coordinate the design of permanent solutions with traffic management, dewatering and temporary works.

This scheme is located in a restricted environment with many environmental challenges, RPS assessed and implemented extensive ecological commitments from Ecology Statements into the detailed design and assisted in coordinating further surveys to identify potential ecological constraints (mammal, geomorphological, hydrological). RPS provided suitable and practical mitigation measures to ensure compliance with best practice and minimal / no impacts during construction.

Image: courtesy of Iain Ferguson