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The missing link

Highways A8

A project to upgrade the A8 between Glasgow and Edinburgh is in full swing, to the eventual delight of motorists along Scotland's 'missing link'. Diarmaid Fleming reports.

Ask Scottish roads engineers what the 'missing link' is, and they'll tell you it's not some Rab C Nesbitt lookalike in Pictish garb, but a missing stretch of motorway on the road connecting its two largest cities, Glasgow and Edinburgh.

What starts and ends as the M8 becomes the A8 for a stretch near Coatbridge, as most motorists who become snarled in its rush-hour jams will know too well.

As well as being Scotland's main artery, the road bristles with junctions, and acts as a significant radial route serving Glasgow and a through-traffic route past Bellshill, Coatbridge and Airdrie. Congestion occurs at all six junctions while, with no hard shoulder, breakdowns cause misery.

Traffic from local roads added to the flow between the two cities make it Scotland's busiest road - carrying around 75,000 vehicles a day with peaks of 6,500 an hour. In road engineering terms, the A8 is Scotland's biggest headache.

The Central Scotland Transport Corridor Studies group, engaged as part of the 10 year transport review, recommended to the Scottish Executive upgrading the road to three lane motorway standard.

But the existing junctions pose huge design challenges which are being worked on at present, and will take some years to resolve. Retaining some or all of the junctions at their present locations would breach motorway standards because they are too close together. A new junction layout to motorway standards would mean extensive redesign of feeder roads.

Meanwhile the high traffic volumes have worn out the existing road. This spring contractor Balfour Beatty, working with its designer Scott Wilson, will finish work started in summer 2002 to upgrade the A8 over an 8.4km stretch between Baillieston and Newhouse.

Describing its condition, Balfour project manager Simon McCormick does not mince his words. 'The road is shot to bits, ' he says.

Patchwork repairs were no longer an option. 'It wasn't effective to maintain. We were facing having to do major emergency work and it was not sustainable, ' adds client, Scottish Executive's consultant Carl Bro's principal engineer, Malcolm Durie.

Key to carrying out the work was the need to minimise traffic disruption, and an advanced 'specimen design' was carried out prior to the start of the contract. This approach was adopted because of the complexity of the works with the six junctions and the need to keep traffic flowing.

The works also involved construction of a hard shoulder in each direction, to provide holding areas for broken down vehicles and access for emergency services as well as providing additional lane space during maintenance work.

Balfour Beatty won the contract for £25M, but with lateral thinking, came up with an alternative that would save £2M.

'Major British Telecom services were routed along the northern end of the road, including television links between Glasgow and Edinburgh, ' says McCormick.

Widening the road for the hard shoulders on both sides would demand extensive protective measures to prevent damage to the services, which could have had astronomical cost and time implications. The alternative proposed keeping the same kerb line at the north edge, except where interfacing with bridges, avoiding the need to interfere with the services.

With lane 'occupation charges' of up to £15,000 per lane per day, complex traffic management measures were developed to minimise closures.

Whatever the outcome of design decisions on motorway upgrade, the revitalised A8 carriageway will still be in use.

'The design is for a long life pavement, giving 40 years' life without structural maintenance, ' says Durie. 'Only surfacing work will be required every 10 years.'

But making the most of the road - not just in terms of width - is a remarkable feature of the job. A detailed assessment of the quality of the existing road was undertaken to examine what work needed to be done to bring it up to the required standard.

'Reconstruction is much more weather dependent, because you are into earthworks, so we look at what we need to rebuild and what we can overlay, ' says Scott Wilson design site representative Tom Bryson.

'The original road was built in the 1930s, with the modern road built in the 1960s. There is variability in the type and thicknesses of the different materials used but some of it has lasted quite well, ' he adds.

Some layers have been very thin, while others, notably the old construction with boulders in clay, has given a good quality road substructure. Inspections have revealed around 900mm of old carriageway with 600mm of blacktop overlaid over the years.

'During lane occupations, we can carry out deflectometer and ground penetration studies to assess the condition of the road and predict what expected life is left in the road, ' says Balfour Beatty operations director Russell Rennie. Cores are also taken for comparison as a check.

Bryson explains that the road is divided into carriageways, and then subdivided into 50m long stretches. The work done - overlay or reconstruction - depends on the condition of each patch. The older westbound carriageway appears to have needed less work.

With class 6F3 planings used in the capping layer which permits bituminous content, the Aggregates Tax has helped encourage recycling materials from the old road for use in the upgrade. Standard materials are used in the HMB35 road base and binder, while a low noise surface course is being laid.

To prevent motorists having to negotiate 8km of cones, the road has been split into four zones, with work planned over two zones at a time.

Safety to workers is provided by Varioagard Barriers, while Celtic cousin SIAC is installing a slip-formed lightly reinforced concrete central reservation barrier. The wet concrete is hacked out with pick and shovel to form a gap for lighting columns.

Speed restrictions of 40mph have been imposed to regulate traffic flow, rather than allowing a 'concertina' effect develop from vehicles travelling at different speeds. Four speed cameras enforce the restriction, blithely ignored by some motorists at the start of the job, with around 400 pictures a day taken by each camera.

At £60 a time, fines at this rate would have topped £50M over the 80 week contract period, more than paying for the £23M cost of the job. Perhaps the word got around once the fines began arriving, but the rate has dropped considerably with most drivers now slowing down.

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