Twyning Green section (J8 to J9)

The first section, commenced at the Ross Spur Interchange with the M5 at Strensham and extended across the alluvial flood plain of the River Avon at Bredon for 1.8 miles. The successful Contractor was Christiani-Shand, the tender price was £1.6m and the contract, which commenced in August 1967, was for a period of 30 months. A feature of this length of the motorway was the construction of a high embankment on alluvium which necessitated the surcharging of the embankment with ten feet of extra fill for a period of 21 months before constructing the drainage and pavement. Also, there were two long-span steel bridges over the River Avon and the adjacent flood relief channel. The construction of the length of embankment between the two bridges required special monitoring to measure the water pressure in the underlying soils and settlements so that the risks of slips underneath the embankment were avoided. There was a deficit of some 476,000 cu.yds. of embankment filling material which had to be imported.

M5 Twyning to Tewkesbury (J8 to J9)

Contract 1B extended 4.8 miles from the River Avon flood plain to the A438 road at Ashchurch where a two level roundabout interchange was constructed. The scheme, which provided a partial bypass to Tewkesbury, was let to Richard Costain & Co Ltd. at a tender sum of £3.39m and commenced in August 1968. Ten bridges and two culverts were built and earthworks amounted to about 1,242,000 cu.yds.

M5 Gloucester - Cheltenham (J9 to J12)

Contract 2/3 was the longest contract on the M5 covering a distance of 12.5 miles. It was let to a consortium of Cementation and Fairclough at a tender price of £10.2 m commencing in May 1969. The interchange on the A438 road on the more northerly Costain Contract only enabled a partial Bypass to Tewkesbury so there was a requirement in the contract for Cementation-Fairclough to complete the section of Motorway from the A438 to the next interchange at Piffs Elm by May 1970. In addition to the Piffs Elm interchange, which only provided connections in the north facing direction, there was a major three level interchange with the A40 Golden Valley Bypass between Gloucester and Cheltenham. This required five bridges with the Motorway at the lowest level, a roundabout at the middle level and the A40 crossing over the top on a high level structure. In order to facilitate the main contract advance contracts were let for the construction of a railway bridge at Churchdown and for a service culvert at Piffs Elm. The contract required the construction of 23 bridges and 11 culverts. Earth works necessitated 3,795,000 cu.yds. of excavation and importation of 552,000 cu.yds. of filling material.

This section of the Motorway received substantial adverse press publicity which led to a Parliamentary Select Committee Inquiry over allegations that the Contractor had been overpaid for the earthworks. However, after Corduroy and Partners had been employed to undertake an analysis, it was accepted by the Ministry of Transport that the Contractor was not paid more than he was due overall, though early payments were higher than they should have been. Mr.R Bridle was the Chief Highway Engineer at the Ministry during this period and a letter from him on the subject is included in the archive.

M5 Moreton Valance Section (J12 to J13)

This contract commenced in June 1969 and was completed at the same time as the more northerly Cheltenham section in March 1971. The length was 6.3 miles and the contract was awarded to Costain- Green Consortium for a tender price of £5.5 million. A railway bridge at Haresfield was constructed as an advance contract by Turriff. There were two interchanges on the section, an elevated roundabout at Stroudwater, and with the A419, where South facing slip roads were provided. The disused Stroudwater canal was filled in adjacent to the interchange. Where the main carriageway crossed the disused Gloucester Aviation Airfield it made use of the main runway which had been designed to cope with the Javelin Jet Planes; the taxi ways were broken out and restored to farm land and the material used in backfill to structures. The bridges at the Stroudwater Interchange had decks requiring 1,380 cu.yds of concrete. These decks were constructed in a continuous concreting operation over 24 hours (unusual at that time) by making use of mobile concrete pumps. The earthworks required approximately 1,794,000 cu.yds. of excavation and the importation of about 372,600 cu.yds. of filling material. In addition to the railway bridge there were twelve other bridges.

M5 Michael Wood Section (J12 to J13)

This section was 8.2 Miles long and crossed open farm land, skirting the edge of the Cotswold escarpment. In the area of Michael Wood the geology was very complex. There were twelve bridges including two over line railway bridges. The Michael Wood service area site was within this length. The earthworks involved 2,415,000 cu.yds. of excavation and 317,400 cu.yds. of imported filling material. The Contract, which started in November 1969, was let to a Consortium of Wimpey and Kier for a tender sum of £5.6m. It was opened to traffic in December 1971.

M5 Alveston Section (J14 to J15)

This 8 mile section was also let to the Wimpy-Keir Consortium for a tender price of £5.85m. The works, which commenced in October 1969, included the construction of the north facing slip roads at the Almondsbury Interchange. When it was opened to traffic in December 1971, at the same time as the previous contract, the M5 was completed between Strensham and the M4. The contract included a "diamond" or single bridge interchange with the B4509 at Falfield which provided connection to Chipping Sodbury also to the A38 and the upper Severnside area including Thornbury. There were twelve bridges on this length a variety of other minor structures, and the earthworks included 1,794,000 cu.yds. of excavation together with the importation of 317,400 cu.yds. of filling material. A geological fault near the Little Avon river has caused a sharp change in the geology of the area, to the north lies the Keuper Marls and to the south the mudstones and limestones of the Falfield beds. At Milbury Heath the route required a cutting thirty feet deep in old red sandstone.

M5 Almondsbury Section (J15 to J16)

This section of the Motorway was built as part of the M4/Almondsbury Interchange construction and unfortunately no details are currently available.

M5 Filton By Pass to Avonmouth Section (J16 to J18)

This section of the Motorway commenced at the southern end of the Filton Bypass, which was completed by Gloucester County Council in 1962, and ended at the Portway between Bristol and Avonmouth. A link road, also subject to motorway regulations, three quarters of a mile long, connected a roundabout at the Portway with the Motorway. The length of the contract was 4.2 miles and it was let to A.E.Farr Ltd. in March 1967 for a tender sum of £3.67m.

At Hallen a mile long cutting was excavated, with a maximum depth of about 60 feet, which generated 1,587,000 cu.yds. of filling material. In addition there was a requirement to import 745,200 cu.yds. of materials for embankment construction which included selected granular material, common fill and fly ash. The rate at which these materials were required placed considerable pressure on the contractor. The railway bridge over the motorway at Hallen was constructed in advance of the main contract. West of Hallen the motorway is on low embankment until it rises at the approach to the Avonmouth Bridge. The side roads and the railway cross over the motorway on high embankments. These embankments rest on a plain composed of alluvium with some peat layers.

During the design stage it was decided, from preliminary soil surveys, the alluvium required special earthworks treatment as calculations showed that if common fill were used on the high embankments there would be failures of the underlying ground before the full height could be constructed . Furthermore settlement of the underlying material would be very slow and it was estimated that 80% would occur after the Motorway was completed. Due to the lower weight pulverised power station fly ash could be used to form embankments of the required heights; so it was decided to undertake an embankment trial to verify the assumptions and to obtain experimental data. As a result, a system of temporary surcharging of the embankments to accelerate settlement was determined and included in the contract. These ground conditions also posed difficulties for drainage culverts and service pipelines under the embankments which also required special measures in construction.The design measures and research which were undertaken is the subject of a paper (and subsequent discussion) in the Proceedings of the Institution of Civil Engineers by N.J.Dallard F.I.C.E. of Freeman Fox and Partners in June 1971 Volume 49 and April 1972 Volume 51 entitled "Design and construction of embankments on an alluvial plain". This paper gives a detailed account of the experimental work and the measurements when the earthworks were undertaken. Granular layers were placed beneath the embankments which were temporarily surcharged to accelerate settlement. The settlement period written into the Contract was 630 days but results of on site monitoring of settlement and pore- water pressures showed that the surcharge could be removed some 130 days earlier and thus the section of motorway was opened three and a half months before the contract date.

The experience gained from the work at Avonmouth were employed in work on later contracts in further Southwest on the Somerset levels. The research by the Road Research Laboratory is reported in document LR419

Avonmouth Bridge (J18 to J19)

As a result of routing the M5 to the West of Bristol it was necessary to cross over the tidal estuary of the River Avon, which has a tide range of some 40 feet, and the adjacent roads and a railway. The Consulting Engineers, Freeman Fox and Partners, who had already designed box girder structures elsewhere in the World, prepared the design using continuously welded twin box girders to achieve an overall width of 132.5 feet. The width catered for dual three lane carriageways and hard shoulders, a central reservation, a cycle track and footway. The design allowed for the conversion of the hard shoulders, at a later date, into carriageways and the cycle track and footpaths into new hard shoulders. The main span over the estuary is 570 feet long with a clearance of 100 feet over high water. The anchor spans are 370 feet long. Due to low bearing value of the ground on the flood plain adjacent to the bridge it was necessary to construct approach viaducts of ten spans on the north side of the bridge and seven on the south. The overall length of the total structure was 4550 feet. The contract for the bridge was awarded to Fairfield-Mabey of Chepstow for a tender sum of £4.2 million. and work commenced in 1969.

Fairfield-Mabey placed a domestic contract with Tarmac Civil Engineering (now Carrilion Construction) for the foundations, piers and deck concreting works. Work on the foundations began immediately and were substantially complete in early 1972. This was in line with the planned opening date in 1972, itself part of the overall programme of extending the M5 southwest

Prior to the letting of the contract for the bridge the Department of the Environment had become concerned about the failure of some continuously welded steel box bridges and appointed a committee chaired by Professor Merrison to examine the criteria for the design of such structures. In May 1971 the Department distributed the first interim rules prepared by the Committee. As a result it was necessary to re-appraise the whole Structure and make considerable changes to the design. Considerable stiffening and/or thickening of plates was required and the combined effect of the design and workmanship requirements of the rules doubled the work at site joints. The redesign led to a considerable delay to the Bridge completion and this was further aggravated by industrial action by the site welders who, because of the extra strengthening, recognised their strong bargaining position and demanded more money. The combined effect of these problems led to the granting of a two year extension of contract with the opening of the bridge in May 1974.

As stated earlier the M5 north of Avonmouth became a continuous dual carriageway Motorway to Birmingham in December 1971. Hence for a while traffic from the motorway heading on towards the Southwest had to travel through Bristol by way of the Portway and the Cumberland Basin complex and then into Somerset on A38. Meanwhile construction of the motorway further southwest between Avonmouth Bridge and Highbridge had commenced in a series of contracts before May 1971 and the completion was January 1973.

The consequences, in Bristol and North Somerset, of the delay of nearly eighteen months in the opening of the Avonmouth Bridge resulted in Motorway traffic flows discharging on to the local road network. The local County, City and District Councilors became very concerned about the potential effects and a conference chaired by a Minister, Mr. Keith Speed, was held to discuss how the situation could be alleviated. At this meeting the County Surveyor of Somerset's representative put forward proposals for a one way signing system from the interchange at Gordano, south of Avonmouth. The scheme, which needed the construction of minor highway improvements, required the signposting of northbound traffic from junction 19 via the A369 to the Cumberland basin and then the A4 Portway to Junction 18 at Avonmouth: the southbound traffic was signed onto the Portway at Avonmouth and then onto the Cumberland Basin leaving on the B3128 through Failand and then via a minor road through Portbury to junction 19. The Councils involved approved the proposal and despite the need for a Public Inquiry the works were completed and the signing installed in time for the opening of the motorway to Edithmead. Thus the worst of the congestion effects were contained for the period until the completion of the Avonmouth Bridge in May 1974.

M5 Gordano Valley

This contract, which commenced in April 1970, was let to Cementation Ltd. for a tender sum £5.7m. It started at the south abutment of the Avonmouth Bridge and extended to Clapton Wick in the Clevedon Hills. It included the construction of the elevated roundabout interchange with the A369 at Portbury and the adjacent Service Area. On sidelong ground in the hills the works were mainly in rock cutting in massive limestone. In order to accommodate the sidelong ground the two carriageways were constructed at separate levels which varied up to 30 feet. In order to support the lower northbound carriageway a crib wall comprised of interlocking precast concrete units infilled with rock was built and to support the higher carriageway a reinforced concrete retaining wall, tied back with rock anchors, was used.

To cross over two adjacent valleys at Wynol Farm twin parallel prestressed viaducts, some 1600 ft long and up to 100 ft high were built and are a feature of this length of Motorway. Access to the site of the viaduct was extremely difficult. In all nine new bridges and 1.5 m cu.yds. of excavation, of which 60% was rock, were required on this 5 miles of M5.

M5 Clevedon Hills Section (J19 to J21)

There are many outstanding Civil Engineering works associated with the M5 but none were more demanding than the section through the Clevedon Hills. Fortunately Mr. Walter Eyre, the Project Manager for Freeman Fox and Partners, has donated a number of important personal papers to the Archive: these illustrate clearly the difficulties encountered by both the designers and the contractors in successfully completing the construction. Amongst the papers are explanations of treatments to stabilize different conditions encountered in the rock faces which are an excellent example of Civil Engineering application. Also included is a copy of a paper presented by Mr. M.G. Lewis at a technical symposium in Columbia in 1974.

The Contract for this 8.7 mile section was awarded to John Laing for a tender sum of £10.73m. the commencement date was December 1969 and it was opened in January 1973. The route rises along the north face of the hills and passes through a saddle before descending to the Congresbury Yeo plain of the Somerset levels. Two interchanges were constructed at Clevedon and St. Georges at Weston-super-Mare. The greater part of the rock cutting through the hills was in the limestone mass which contains a thrust fault, in places the rock was fissured and required extensive grouting and over 4000 rock bolts were installed. The maximum depth of cutting was about 33 ft.


Based on further development of the work on alluviums at Avonmouth, trial embankments were erected and extensive testing carried out on the soil conditions on the Somerset levels. These trials and calculations showed that the maximum safe height for embankments was about eighteen feet, but as side road and interchange embankments were about 25 feet in height, light weight pulverised fuel ash (PFA) had to be used. The importation of large quantities of PFA was organised by rail to a specially constructed railway siding. In order to speed up settlement of the under lying silts the motorway embankments were surcharged at a carefully controlled rate and left to settle for a period of twelve months. Drainage below the banks was achieved by placing a 3 foot layer of rock onto the unstripped vegetation. In total some 1,794,000 cu.yds. of filling materials were imported including 897,000 cu.yds. of PFA. 14 bridges were constructed mainly on piled foundations: foundations for bridges on the levels could not be piled until settlement surcharge material was removed.

When this section of motorway was designed Somerset County Council were planning a new route to Western-super-Mare from Bristol. The first section, from the Cumberland Basin complex in Bristol, by-passing Long Ashton, was already open and the line was being protected to the M5 Clevedon interchange. Accordingly provision was made in the width of the central reservation of the section of the M5 from the Clevedon interchange to St. Georges interchange with the A370 for a future widening of each carriageway to four lanes. However after the formation of the Avon County Council in 1974 the County Scheme was Abandoned.

Mendip Hills Section (J21 to J22)

This section passed through a saddle near the western end of the Mendip Hills and crossed a further part of the Somerset levels ending at the interchange with the A38 at Edithmead. The contract, which was awarded to A.E.Farr Ltd (later to become Bovis) for the sum of £8.05m, commenced in December 1969 and was completed in January 1973. The length was 8.05 miles and the work included the construction of a "trumpet" interchange at Edithmead. The earthworks required 2,070,000 cu.yds. of common excavation, mainly in marl, some 97,000 cu.yds. of excavation in rock and nearly 1,.100,000 cu.yds. of imported material including 207,000 cu.yds. of PFA.

On this section of motorway, the alluvium extended to a maximum depth of some 90 ft and trials of embankment loading and failure were undertaken at East Brent in advance of completing the design. The criteria derived from these trials established the practice for embankment construction and piling work at bridges. In the latter case the problem of the settlement of the alluvium under load introducing negative friction on piles causing overload or drag down, was of real concern but the trials demonstrated that coating the piles overcame any difficulties.

As on the previous contract, arrangements were made for the importation of PFA from South Wales by rail and a handling centre was set up to transfer the material into lorries at a temporary siding in the disused Highbridge Locomotive Works. The material was used to form the embankments above the height of 12 ft.. In order to accelerate the settlement of the alluvium, the motorway formation was surcharged with a rock blanket for a period of a year.

Twelve bridges were constructed on this section, nine of them were on piled foundations. Additionally, the contract included a provision for the embankment surcharge material to be hauled southward onto the next length of the Motorway to form an embankment between Edithmead and the River Brue; It also included the associated advance drainage works.



Archive Information

The M5 in the South Western Region


The full archive for this scheme is stored at the Somerset Heritage Centre.  Click to see details of this record office, then delete the popup page to return.  Its accession number is: M/582 Catalogue reference: A/BXB.  There is some additional material stored at Gloucestershire Archives.  Click to see details of this record office, and the necessary access information, then delete the popup page to return. 



M5 Motorway


Official papers and reports



Copy of the South Western Road Construction Unit Programme issued December 1969.
(1 document)



Report of a working party of the Department of Transport entitled, 'Route Location with Regard to Environmental Issues'.
(1 document)



Pamphlet entitled, 'Trunk Road Proposals - A Comprehensive Framework for Appraisal'.
Prepared by The Standing Advisory Committee on Trunk Road Assessment.
(1 document)



Copy of the Department of the Environment South Western Road Construction Units 7th Annual Report.
(1 document)


Pamphlets and opening brochures



Pamphlets entitled, 'M5 Motorway in Gloucestershire and Somerset.
Prepared by Consulting Engineers Freeman Fox and Partners to mark the completion of the M5 as far as Edithmead.
Includes an earlier draft version.
(6 documents)



Opening brochure for the Gloucester-Cheltenham section of the M5 in March 1971.
(1 document)



Opening brochure for the Avonmouth section of the M5 in August 1969.
(1 document)



Opening brochures for the Avonmouth Bridge section of the M5 in August 1972.
(2 documents)



Opening brochures for the Dunball to Huntworth section of the M5.
This was opened on the 18th Dec 1973 by the Rt. Hon. John Peyton, Minister for Transport Industries.
(2 documents)



Opening brochure for the Chelston to Willand section of the M5 in October 1976.
(1 document)



Opening brochure marking the completion of the M5 upon the opening of the Exminster section by the Prime Minister the Rt. Hon. James Callaghan MP on 27th May 1977.
The brochure contains information about the whole of the M5 from Strensham, Worcestershire to Pearces Hill, Devon and includes a separate sheet listing those who were presented to the Prime Minister.
(1 document)



Copies of a pamphlet issued to members of the South Western Association of the Institution of Civil Engineers, who attended a visit to view motorway construction in the South West on the 10th September 1970.
One copy includes the address of welcome from the Director of the Southwestern Road Construction Unit, Mr P G Lyth.
(2 documents)



Pamphlet issued to members of the South Western branch of the Institution of Highway Engineers on the occasion of their visit to view construction works on the Edithmead to Dunball and Dunball to Huntworth sections of the M5 on the 27th September 1972.
(1 document)



Pamphlet issued to members of the South Western branch of the Institution of Highway Engineers on the occasion of their visit to view construction works on the Blackbrook to Chelston section of the M5 on the 25th July 1973.
(1 document)


n.d [c.1974]

A pamphlet prepared for the proposed Pearces Hill to Pocombe Link Road A30.
(1 document)



Copies of a paper entitled, M5 Motorway in Devon'.
(4 documents)


n.d [c.1970s]

An extract from the magazine New Civil Engineer about the Avonmouth Bridge and a publicity paper by the contractor Fairfield Mabey.
(2 documents)



An article about the construction of the M5 from the Avonmouth Bridge to Dunball.
(1 document)



An article from Construction News about the construction of the M5 from the Avonmouth Bridge to Dunball.
(1 document)



Extract from a magazine concerning the Edithmead to Dunball section of the M5.
(1 document)



Copy of the Proceedings of the Institution of Civil Engineers entitled, 'Design and construction of embankments on analluvial plain', by N J Dallard.
(1 document)



Copy of the Proceedings of the Institution of Civil Engineers with a discussion on A\BXB/2/2/17.
(1 document)



A report prepared by Devon County Council entitled, 'The Motorway Into Devon: The Challenge'.
(1 document)



Chapter 3 from a book by Michael Hawkins, the former County Engineer of Devon, which refers to the M5.
(1 document)



Copies of a map of the M5 motorway from Strensharn to Edithmead, prepared by Freeman Fox and Partners.
(2 documents)



Map of the M5 motorway from Avonmouth to Puriton.
(1 document)



Map of the M5 motorway fromEdithmead to Willand.
(1 document)



Map of the M5 motorway fromEdithmead to the West of Exeter alternative routes.
(1 document)


Recollections andcorrespondence



Letter to F D J Johnson from Brigadier Stanley Baldwin containing his personal recollections.
(1 document)



A paper entitled, 'Bridging the Gaps', by Michael Clerk, a former section engineer in the RCU HQ.
(1 document)



Two letters from Professor R Bridle suggesting sources of material for the Motorway Archive project, together with anecdotal memories.
(2 documents)


Newspaper cuttings



Copy article on the M5 from the magazine Roads and Road Construction.
(1 document)



Newspaper cutting on the M5 from the Western Daily Press
(1 document)



Copy newspaper cutting on the M5 from the Cheddar Valley Gazette.
(1 document)



Newspaper cutting about the Exminster section of the M5.
(1 document)




1974 83

photographic prints (mostly black and white) of various sections of the M5 Motorway.
(1 bundle)



11 mounted photographs of the M5 motorway under construction and once completed.
(11 documents)


[c. 1970]

4 photographs of artistic representations of proposed bridges on the M5 Motorway.
(4 documents)


Papers of the Trust



Executive summary report of the Motorway Archive Trust project.
The report was compiled by F D J Johnson, former County Surveyor of Somerset and former President of the County Surveyors Society. It provides a history and context to the construction of a motorway network in South West England.
(1 document)




The Twyning Green (J8) to Edithmead (J22) section of M5 Statistics.

Section Construction started Opened to traffic
Twyning Green Section (J8 to J9) August 1967 February 1970
Twyning to Tewkesbury (J8 to J9) August 1968 February 1970
Gloucester - Cheltenham (J9 to J12) May 1969 March 1971
Moreton Valance Section (J12 to J13) June 1969 March 1971
Michael Wood Section (J13 to J14) November 1969 December 1971
Alveston Section (J14 to J15) October 1969 December 1971
Almondsbury Interchange to Filton By Pass(J15 to J16) May 1964 September 1966
Filton By Pass (upgraded) to Avonmouth (J16 to J18) March 1967 March 1969
Avonmouth Bridge (J18 to J19) 1969 May 1974
Gordano Valley April 1970 January 1973
Clevedon Hills Section (J19 to J21) December 1969 January 1973
Mendip Hills Section (J21 to J22) December 1969 January 1973