Introduction

Probably the decision which has had the greatest effect on the M5 in Worcestershire was to build it to dual 2-lane standard. It has to be remembered that the Gloucester Section (south of junction 8) was dual 3-lane and the section north of Quinton (junction 3) was dual 3-lane. There seemed no sense therefore in building the middle section in Worcestershire to dual 2-lane. Despite repeated representations from Worcestershire County Council, the Police and particularly the County Surveyor of Worcestershire that dual 3-lane standard was appropriate, The Ministry of Transport refused to budge and thus it became a dual 2-lane motorway. The short sightedness of this decision was to be brought home the hard way when it became necessary to widen the Worcestershire section of M5 at a cost of £123 million. The original 28 miles of motorway had cost just £8 million. Every bridge had to be demolished and rebuilt.

The widening and reconstruction was carried out over a period of about 15 years, and included a variety of widening approaches. This included widening within the existing highway boundaries, and new symmetrical or asymmetrical construction.

The section of the M5 between Junctions 4 (Lydiate Ash) and Junction 8 (Strensham) was designed to dual two lane motorway standards which are below those in current use. In layout, as an example, only 18% of the sight distances between Warndon and Catshill meet full current requirements.

When the design brief was started in 1980, the motorway was carrying 38,000 vehicles daily; by the start of construction in 1985 the flow had increased to 42,000 vehicles per day; it is currently exceeding 100,000 vehicles per day on the widened section south of M42.

The expected life of the carriageways was far less than 20 years when measured in current standard axle terms. Thus the reconstruction of the most distressed areas between Junction 6 and Junction 8 was commenced in 1977 and completed in 1983, well in advance of its eventual widening in the early 1990s.

Concurrently the planning of the combined reconstruction and widening of the remaining motorway between Junction 4 and Junction 6 was commenced. This scheme was divided into four Contracts at an estimated cost of £53M. The work involved the demolition of all the overbridges and the construction of replacement structures together with the extension and sometimes replacement of the bridges carrying the Motorway over roads, a railway, rivers and a canal. Improvements were also made to the Motorway alignment as some bends were too sharp and the whole width of the carriageway was rebuilt as necessary. Completing the M5/M42 junction was combined with the adjacent widening contracts.

Widening and reconstruction of 'live' motorway demands pre-planning and advance works far in excess of similar activities on green field sites. The provision of maximum traffic capacity on the motorway, coupled with working space for the Contractor and adequate diversion routes for traffic overspill are essential pre-requisites. As the highway authority for roads, other than motorway or trunk roads, the County Council was uniquely placed to assist the Department of Transport by ensuring that the optimum balance was achieved on the motorway and on the local road network, which carried both Contractors and diverted traffic. To achieve this objective, advance works costing £5m were carried out. These included improving diversionary routes, re-siting Statutory Undertakers equipment, restoring skid resistance to old carriageways, providing street lighting, strengthening hard shoulders, and providing central reservation crossings.

Comparison of the cross sections showed the dramatic change that had taken place in the build up of motorway furniture. The original empirical design performed extremely well structurally. Although superficially modernised into the intermediate two lane cross section with all the modern aids to movement and safety it still retained inherent weaknesses in alignment, visibility and drainage. Online widening made the updating of these deficiencies difficult but asymmetric widening over 25% of the scheme improved alignment and visibility. Fixed drainage outfalls created problems but drainage was improved considerably to form a more efficient drainage system.

The interpretation of Deflectograph, crack and soil surveys and compliance with DTp recommendations for pavement thickness, presented problems in marrying new to old pavement. The objective to retain as much of the existing pavement as possible was, in many cases, frustrated by the need to break out old hard shoulder, to meet level tolerances at existing underbridges and to produce an acceptable pavement combining both old and new design.

The first widening - Quinton (J3) to Lydiate Ash (J4)

By 1972 traffic flows had reached a level where widening was proposed between Quinton and Lydiate Ash. Widening was carried out within the motorway boundaries. Overbridges were not widened and underbridges either widened or parapets strengthened.

Work finally started on 20 November 1978 when a tender, in the sum of £3.639M, was awarded to A Monk & Co. This was before the days of lane rental but tenderers had been asked to price for both 56 and 72 week Contract periods. The shorter tender period was accepted.

The scheme was 8.4 km long. Carriageways were widened symmetrically about the existing central reservation and the works were contained within the existing motorway boundaries. Continuity of hard shoulder was maintained over the nine widened underbridges but not at the eight unwidened overbridges.

Advance Works to this Contract were necessary and were carried out by direct labour prior to the main Contract so as to keep the main Contract period and traffic disruption to a minimum. These works included -

1. improvement to Quinton Junction to improve traffic flow;
2. removal of the existing and erection of the new permanent traffic signs (this was possible because there was no land take);
3. hard shoulder strengthening for contraflow;
4. re-siting of the communications cable from the verge to the motorway boundary.

The central reservation had to be narrowed over a short distance to accommodate the extra lane at Carters Lane overbridge near Quinton and the northbound carriageway had to be lowered to give adequate bridge headroom when the slope of the hard shoulder was reversed.

Fortunately the majority of bridge headrooms were adequate to allow a 100 mm overlay on existing carriageways. The concentration of work was therefore at the old hard shoulder/new nearside lane and the new hard shoulder.

In cuttings, the slopes of the hard shoulders on the low side of superelevation had to fall towards the carriageway to save under-cutting the toe of the slopes which were relatively unstable in this area. On embankments, a large edge beam or verge wall had to be used to provide stability for the back of the hard shoulder.

Lydiate Ash (J4) to Catshill (J4A)

This contract, let to A Monk & Co, had five existing overbridges and two underbridges. The overbridges were totally replaced, whilst the underbridges were modified and extended.

Unlike the previous two contracts, a substantial proportion of the length of this scheme, including the section containing the underbridges, was widened asymmetrically. Using construction methods developed previously, this meant that 2 + 2 traffic working was possible at all times except for two short periods, to enable construction of widened carriageway under Lydiate Ash junction.

Overbridge structures were generally single span and extensive use was made of steel for deck spans, with girders being lifted in during overnight closures of the motorway, enabling the contractor to continue work on deck construction with minimal disruption of traffic. However, the side road structures at the southern end of the scheme spanned both the M5 carriageways and M42 slip roads. This resulted in longer than normal span lengths and the need for two span structures with central piers and hence "island site" working.

Construction of these centre piers was completed in conditions of limited access and working space and extensive use was made of precast concrete safety barriers in these locations to protect the working area.

Demolition of some of the existing bridges was carried out using tried and tested methods; footbridge decks at Claypit and Woodrow Lane were lifted off in one piece at night and broken up at ground level, whilst Clockhouse Bridleway bridge was brought down using controlled explosives. The size of the structures at Rocky Lane and Stourbridge Road along with the proximity of adjacent property, however, required the use of new methods specifically suited to these environmentally sensitive areas. These post-tensioned concrete structures were 'cut' into longitudinal slices using a recently developed machine mounted saw. The sections were then removed during overnight possessions of the motorway.

In addition to replacement and modification of the existing structures, two standard DTp design sign gantry structures were erected to carry advanced warning signs and matrix signals, whilst a third gantry structure was designed as an integral part of the footbridge at Claypit Lane.

Catshill (J4A) to Rashwood (J5)

The 8.5km contract, M5/2, from Catshill to Rashwood was completed in time for Christmas 1986, in 85 weeks, thus cutting the Contract period by some 28 weeks. This early completion provided three lane motorway on M5 ready for the opening of M42 southern turn which was connected to M5 at Catshill on the 18th March 1987. Work continued throughout the winter of 1985/1986 with the anticipated suspension of earthworks and asphalt laying as determined by weather and temperature; although the use of EVA in the wearing course did facilitate working which otherwise would have been impossible. The Contractor was A Monk & Co.

100,000 tonnes of recycled cement bound granular base (CBGB) and blacktop, taken from superceded sections of the scheme, were incorporated into the new pavement structure as a capping layer on this contract.

The scheme included sixteen existing structures, six overbridges, six underbridges and four culverts. The overbridge spans (two side roads, three farm access and one footbridge) were all too short and the under bridges too narrow to accommodate the proposed widened motorway.

The essence of the design philosophy was simplicity of structural form, to minimise disruption to traffic and bridge users and also allow the Contractor to carry out key operations during the limited carriageway possessions available.

To achieve these aims the new structures were built alongside the existing which remained in use until the new work was complete. The new overbridges are of steel/concrete composite construction, five being of single span configuration and one a two span structure crossing both M5 and M42 slip road. The plate girders with spans up to 49m were manufactured by Fairfield Mabey at their Chepstow Works. Foundations were generally spread footing founded on sandstone at the northern end of the scheme or marl at the southern end, although Upton Warren overbridge was founded on bored cast insitu piles.

During overnight possessions of the motorway the new deck girders were lifted into position in the form of braced pairs. These were 'boarded out' to allow the Contractor to continue construction of the new deck the following morning over the live motorway.

Demolition of the existing structures was also carried out during the night time possessions. The single span farm overbridges were demolished using controlled explosives, whilst the four span side road bridges were 'cut' and lowered to the ground on jacks or broken up using machine mounted hydraulic breakers.

Underbridges were generally widened symmetrically using a similar form of construction to the existing. Some of the existing decks were strengthened by overslabbing and in two cases completely replaced. As with the overbridges, foundations were generally spread footings with the exception of the two most southerly bridges where bored cast insitu piles were employed. Although at face value less spectacular than the overbridge structures the design and construction of the underbridges did pose a greater challenge and great care was taken to ensure the new extensions did not impart additional load to the existing structures.

In addition to replacement and extension of the existing structures, three new sign gantries were required to carry advanced direction signing for the proposed M42 junction at Catshill. These structures have been fabricated to standard Department of Transport designs.

Rashwood (J5) to Warndon (J6)

Contract M5/1 between Rashwood (J5) and Warndon (J6), let to Tarmac Civil Engineering (now Carrilion Construction), started in December 1986 and was completed 28 weeks ahead of programme. All commitments of 2 + 2 contraflow working were achieved for Easter, Spring and August Bank Holidays.

The provision of a licensed strip parallel to the motorway proved essential in providing access to the site for Contractors, which still remains one of the major problems on this type of work. This provision, of course, complicated the completion of Accommodation Works, which in some cases, had to be completed in various stages. The balance of traffic capacity and flow achieved on motorway and diversion routes proved satisfactory in that traffic delay times of only 15 to 20 mins in 2 + 1 contraflow were acceptable and the Contractor did not experience exclusion from his own works by queuing traffic. At the design stage this possibility was worrying and the provision of an asphalt plant on site proved beneficial.

On this 8.7 km section of the motorway all 12 existing structures were underbridges. Eleven of these were single span structures, including four side road bridges, four farm underpasses, one railway bridge and two culverts, with one two-span structure over the Worcester-Birmingham Canal and a farm track.

The farm bridges were widened by extending at each end of the structure using a similar form of construction to existing, while decks were extended and strengthened by overslabbing. At the railway bridge the existing abutments were widened and strengthened and the deck replaced by new prestressed beams with in-situ concrete infill. Where structures were widened care was taken, in both the design and construction method, to ensure minimum load transfer between existing and new elements. The other five structures were totally replaced.

Foundations are generally bored cast in-situ piles, except at the northern end of the scheme where spread footings have been used at the Railway bridge and Rashwood Farm Underpass.

As with the previous contract the design recognises the need to minimise traffic disruption and the new structures have been designed to allow the Contractor to follow a sequence of construction tailored to meet traffic constraints. In order to satisfy these requirements extensive use has been made of beam and slab decks, with both steel plate girders and prestressed concrete beams being utilised.

At the Southern end of the scheme the new side road and canal bridge structures span (up to 43m) over the top of the existing. New bank seats were constructed behind the existing abutments, the side roads staying in use except for short closures, for demolition of existing decks and lifting in new steel girders. Where necessary these operations were carried out during overnight possessions of the motorway.

At Hanbury Road underbridge the motorway was widened asymmetrically. Here a section of new bridge is constructed outside the existing motorway confines. When this is complete traffic is switched onto the new section, allowing sequential demolition of existing and construction of the inner section of the new bridge.

In this contract, recycled cement bound granular base (CBGB) and blacktop was crushed and used as a blended material for type 2 fill.

Warndon (J6) to Strensham (J8)

In 1986 Howard Humphreys & Partners won by competitive bid the commission for the design of this section. In order to widen this last two lane section expeditiously a 'fast track' approach was to be adopted for the design and consultation period. Despite the need to go to Public Inquiry in 1989/90, procedures were completed allowing tenders to be invited early in 1991 to widen this section of M5 using the new parallel widening technique, which involves building an entirely new three lane carriageway and hard shoulder alongside the existing motorway. Traffic on the existing motorway remains largely undisturbed and the need for contraflow is eliminated. The sequence involved is shown here.

The advantages of parallel widening over on-line techniques are:

• Improved safety for both travelling public and construction workers.


• Reduced disruption to traffic flow, no contraflow.


• Shorter construction period, as larger areas of the site are available to the contractor.

The contract was awarded to Laing Civil Engineering with a winning bid of £59.4m. As part of the bid Laing also shortened the Contract period from the 145 weeks included in the Tender Documents, to 96 weeks. Subcontracts for fencing and site clearance were arranged to ensure work commenced in earnest on 1st July 1991. Approximately 26km of boundary fencing was erected in the first four weeks, taking a large proportion of the total UK supply of treated timber.

The scheme involved widening 22km of dual two lane motorway and included complete replacement of nineteen overbridges and construction and/or replacement of five under bridges and nine culverts. The three existing interchanges at Warndon (J6), Whittington (J7) and Strensham (J8) were also reconstructed.

At Warndon (J6), the existing two bridge grade separated roundabout was replaced with a similar layout of larger diameter. Phased closure of the existing slip roads was permitted. Land take for the new junction required the demolition of part of the existing Motorway Maintenance Compound. A new facility had therefore been constructed to the north of the new junction under an advance contract which was substantially completed prior to the start of the widening contract.

The existing junction at Whittington (J7) consisted of a single overbridge 'dumb-bell' layout. This was replaced by a grade separated two bridge roundabout. However, closure of slip roads here was not permitted.

At Strensham (J8), the existing M50 joined M5 in a free flow layout, albeit with horizontal curves substandard to current requirements. The anticipated traffic growth on M50 did not justify a new free flow junction layout which to current standards would have had a large environmental impact in this area. Thus the new junction is a standard grade separated two bridge roundabout with M5 crossing over M50.

The widening required demolition of part of the existing northbound Service Area just to the north of Strensham. A larger improved service area was constructed under a separate contract, about 1 km north of the original site. During the widening contract limited facilities were maintained at the original site until the new Service Area was completed.

Materials encountered along the route of M5 include rocks of the Mercia Mudstone group between Warndon & Baughton Hill, whilst to the south of this, Lower Lias clays predominate. The whole area is overlaid with terrace deposits and significant volumes of alluvium in some locations.

Total excavation for the contract was some 1.3 million cubic metres with a requirement for 280,000 m³ of imported material, whilst approx. 300,000m³ of material unsuitable for use in embankments was incorporated in landscaping and noise mounds.

The contractor made his own arrangements for a borrow pit immediately adjacent the site to supply imported material. This facility meant that material could be distributed using site going dump trucks, thus limiting the number of lorries on the side road network. The borrow pit area has now been landscaped and returned to agriculture.

The programme strategy required that earthworks be substantially complete within the first six months of the contract. Earthworks Subcontractor C A Blackwell set about this task with a large fleet of heavy plant and assisted by an unusually mild winter made excellent progress and was largely able to achieve the programmed aim.

A 350mm capping layer was required to protect the earthworks and provide a stable platform from which to construct the pavement. To form this layer use was made of recycled surfacing materials obtained from the site and other adjacent contracts. A smaller amount of crushed concrete from bridge demolition was also utilised.

As the design for one of the carriageways used the existing motorway pavement with an overlay, the contractor was allowed only the flexible pavement options. In this case the contractor's chosen pavement materials were 150mm type 1 sub-base, 125mm rolled asphalt lower road base, 235mm dense bitumen macadam upper roadbase and 40mm rolled asphalt wearing course, giving a total construction thickness of 550mm.

The contract required that all bituminous materials be supplied from a plant established adjacent the site. Production of surfacing materials was sublet by Laing to Bardon Roadstone Ltd, who set up twin batching plants in the contractor's main compound at Norton. Each plant was capable of producing any of the materials required and had an output of 220t/hour. Access to and from the batching plant was established directly from M5, again minimising the number of delivery trucks on local roads. At the height of the production programme 4000t of material per day was supplied from the on-site plant to be laid by up to 5 pavers.

All the overbridges except one are of two span configuration, the longer span crossing the existing motorway. whilst the second span over the new parallel carriageway was extended to achieve better balance and accommodate any future widening. Design of the new structures recognised the need for speed of construction and in particular the difficulties of building over the live motorway. The steel plate girders chosen for the deck spans were designed to be fabricated, transported and lifted as braced pairs, ensuring optimum speed of erection. The number of girders in each bridge varies according to width, with a single pair for farm accommodation bridges and up to four pairs used for the curved structures at junctions.

Girders were fabricated at the Chepstow Works of Fairfield Mabey Ltd. With detailed planning the contractor was easily able to erect all girders for one, or sometimes two bridges within the 10-12 hour night closures. A second closure was utilised to complete fixing of walkways, screens and permanent formwork, which completely enclosed the spans allowing work to proceed over live traffic.

Once new overbridges were complete and opened to traffic demolition of the existing structures could follow. These concrete bridges varied in configuration and size, from single span post tensioned to four span in situ slabs, with the largest deck being some 1000 tonnes of precast beam and in situ concrete infill.

The contractor proposed the use of controlled explosives to bring down and fragment these structures. This method had been successfully used on previous widening contracts and the work was sublet to the same specialist subcontractor Demex Ltd. Following discussions with local Environmental Health Officers, the Police and other interested parties a detailed method statement was produced for control of the events leading up to each blast. Extensive public liaison was necessary to allay concern and warn local inhabitants of the procedures formulated to ensure the safety of all concerned. Although carried out late at night these `bridge blasts' soon became popular spectator events which eventually required provision of additional marshals and a safe viewing area for up to 200 people.

Demolition was carried out during overnight motorway closures, usually 9.00pm Saturday until 8.00am Sunday. Careful planning and close co-ordination with all concerned enabled the work to be completed successfully with few complaints and no significant damage to property.

Although the parallel widening concept removes the need for contraflow, traffic management schemes were necessary for the phased construction at each of the junctions, to ensure safe access to the motorway service area, and for the 50 night time motorway closures for key operations such as bridge beam erection, and demolition. Traffic management changes required advance publicity and extensive signing of diversion routes.

Few environmental mitigation measures were included when the motorway was originally built. However, the opportunity was taken in the widening contract to redress this.

On the non-widened side of the motorway the area of redundant carriageway was used for extensive landscaping and mounding, whilst noise and visual screens were also constructed on the widened side to reduce the impact on adjacent villages and individual properties. The Department of Transport also installed secondary glazing in qualifying properties to alleviate construction and traffic noise.

Wherever possible the existing mature hedge which forms a well established visual screen was retained and in addition the landscape areas were planted during Autumn 1993 with 250,000 trees and shrubs.

The existing motorway lighting was replaced with new high pressure sodium lamps with a greater level of 'cut-off'. The light is directed downwards onto the carriageway, this together with the 'softer' colour reduces glare and overspill outside the motorway, thereby reducing the impact on adjacent inhabitants.

Precautions have also been taken during construction to protect the habitat of wildlife in the area. At one location site clearance of Wych Elms was delayed until the larvae of the White Letter Hairstreak butterfly had hatched, whilst special measures were also necessary when a badger sett was discovered immediately adjacent the works. The badgers' movements were monitored by experts to ensure the animals were not unduly affected by the road building operations.