To the west of London, a 12km stretch of the M25 — the busiest motorway in Europe — has been widened to relieve traffic pressure. A new spur road was also needed to facilitate the exchange of traffic in and out of Heathrow Airport’s Terminal 5. In a joint venture with engineers WSP, our transport specialists developed the concept designs and worked with Balfour Beatty to implement the widening and spur road projects as part of a design & build contract.
Background
The M25 is dual four lane motorway. It has been widened to dual five lanes between junctions 12 and 14, and to dual six lanes between junctions 14 and 15, accommodating up to 200,000 vehicles per day. An additional 8km of new link roads, five new steel composite bridges and 40 new gantries have been provided, as well as modifications undertaken to at least 10 existing significant structures. The UK's Highways Agency required minimal disruption to road users during the 137 week programme, 102 weeks of which were scheduled for on-site works. A comprehensive traffic management plan was implemented that minimised traffic disruption. Dual four lanes were kept open throughout daylight hours and overnight closures were limited.
Novel techniques/Innovations
To facilitate the requirement to keep within the existing highway boundaries during widening works, rapid construction was made possible by the adoption of a unique modular system for the retaining walls. The project was completed three weeks early.
Recycled materials were used for the road construction, including granular fill from the demolition of the old Wembley Stadium. Sensitive lighting, low noise surfacing and acoustically absorbent environmental barriers were selected to reduce the impact on local communities. The project has won a number of awards.
Collaboration with WSP
Ramboll and WSP have collaborated and worked with Contractors on major highway design for over 40 years and have been at the forefront of motorway widening since the first design and build contract on the M25 between junctions 8 and 10 in 1997. Collaboration has continued with ECI contacts for widening the M1 between junctions 6a and 10 and between junctions 25 and 28 and the M25 between junctions 12 and 15. The M25 DBFO Section 4 was the most recent for this relationship bringing the total length of widened motorway to over 100 km.
