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M4 Second Severn Crossing

The location of the Second Severn Crossing and the approach roads M4,M48 and M49 is well documented in the series of prize winning papers published in the Proceedings of the Institution of Civil Engineers Volume120 special issue2 entitled "Second Severn Crossing".

In February 1984 the Government announced that a study was to be commissioned to determine how a second crossing of the Severn estuary might be provided. After inviting tenders for a study the Second Severn Crossing Group comprising Consultants W. S. Atkins and G. Maunsell and Partners were appointed to examine Bridge and Tunnel solutions.

 Management of the whole Project was passed to the South West Regional Office of the Department in September 1987. After a period of extensive study of the various parameters involved, a period of public consultation and the preparation of an illustrative bridge design, tenders were invited in April 1989 for two options:

  1. To design, build, finance and operate the second crossing(DFBO) including operating the first crossing and paying off the existing debt
  2. To design and build the second crossing for staged payment by the Government.

Second Severn CrossingIn April 1990 heads of agreement for the concession were made with the successful tenderer Laing-GTM, a UK /French consortium, for the DBFO option. On acceptance Laing-GTM and their financial backers set up an operating company entitled Severn River Crossing Plc. (SRC) The contractor appointed Consulting Engineers Halcrow SEEE to prepare the detailed design and Gifford & Partners to undertake the check on the design.

Between April 1990 and April 1992 the Parliamentary Bill giving powers to construct the crossing, all the approach motorways and transfer the existing crossing to SRC proceeded through Parliament and became an Act. The Government Agent was able to take possession of all the land required for the crossing on behalf of the Government. The official start date for the concession period was the 28th April 1992 which was also the start of the four year construction period. The total financial package procured by SRC was valued at almost £1000 million to cover the three main aspects of bridge construction, pay back of debt of existing bridge and financing costs. Although the whole Bridge was provided by Severn River Crossing Plc., because in due course it will be taken over by the Government, Maunsell and Partners were appointed as the Government Agent to ensure the whole project complied with the required standards..

As part of the project new link motorways on the Avon and Gwent sides of the estuary were constructed to divert the M4 Motorway over the new crossing and the existing route over the first bridge between Awkley in England and Rogiet in Wales was redesignated M48. In addition a new Motorway link designated M49 was constructed between Avonmouth on the M5 and a new interchange on the M4 at Redwick at the eastern end of the new bridge. Design work for these roads was carried out by the Consulting Engineers W.S. Atkins and Maunsell & Partners (Second Severn Crossing Group). 

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Contract details:



Cost (£M)

Main Estuary Crossing and Toll Plaza



English Approach Roads

Balfour Beatty Ltd


Welsh Approach Road

Costain CE Ltd


British Rail Bridge, Hallen



Rogiet Construction Access



Enhanced Navigation Aids



Advanced Support Structures



Service Diversions






It is a tribute to all concerned with this remarkable project that the new bridge, costing £330 million was completed on time, within budget and without loss of life or limb. The papers to the Institution of Civil Engineers, (a copy is deposited in the Archive) give detailed information on the choice of method and location of crossing; the detail of administrative processes and the design and construction management. Television films were made during the construction phase and a well used visitor information centre existed near the site which enabled many people including parties of school children to learn about the project.