The Stepps by-pass included what was clearly a temporary connection into the A80 with a sharp bend immediately east of the Town. This would inevitably be the southern terminal of the completion project, and two alternative routes were considered. The “offline” proposal continued along the Kelvin Valley, approximately 3km north west of the A80, whilst the alternative continued roughly on the Stepps By-pass line sufficiently to by-pass Moodiesburn before joining the A80 close to the M73 junction. There would then be “online” upgrading of the A80 to join the M80 at Haggs. Whilst both routes had similar economic benefits, the Kelvin Valley route passed through important ecological & archaeological sites. In the final analysis, it was the inability to successfully mitigate the potentially adverse impacts associated with the Kelvin Valley Route which led to the selection of the A80 upgrade Route as the preferred option.

Transport Scotland, an agency of the Scottish Government, awarded the contract for the construction and the 30 year operation & maintenance period to Highway Management (Scotland) Ltd. The contract was valued at approximately £320 million. The scheme was considered as three discrete sections:

Stepps to Mollinsburn comprised a dual two-lane carriageway with hard shoulders, a new Interchange at Mollinsburn, and a new two-level junction north of Stepps. Mollinsburn to Auchenkilns included 2.7km of dual three and dual two upgraded road along the route of the existing A80, extending from Mollinsburn to tie-in to the western side of Auchenkilns Junction. Auchenkilns to Haggs, 7.3km of upgraded road, including dual two-lane carriageways with climbing lanes. The inevitable widening affected several structures.

The Auchenkilns junction, previously an at grade roundabout, had already been reconstructed as a grade separated interchange, at a cost of £22.4m, and opened in 2005. It was said to be one of the most notorious traffic bottlenecks in Central Scotland, carrying around 70,000 vehicles a day - the average traffic flow for the old A80.

Auchenkilns junction

As part of the construction of the M80, an upgraded road drainage system was provided with ponds for the treatment of surface water run-off, the provision of noise reduction screening and extensive landscape planting. On much of the scheme, a concrete central reserve barrier was constructed using a slip-form paver.

Mollinsburn bridge finalProbably the major element in the M80 scheme was the extensive redesign of the Mollinsburn interchange linking M73 to M80, and the surrounding local access roads to Westfield and Mollinsburn. The Mollinsburn bridge is particularly interesting. Originally proposed as a four-span structure, traffic management constraints suggested that it should be designed as a 55 metre single-span bridge (Image right). To reduce traffic disruption, it was actually built in two-spans, with the beams being welded together on a temporary staging (see image below). The beams can be seen being lifted by a rare 1200 tonne crane, which had been borrowed from the Olympic site in London.

Mollinsburn bridge under construction

widening old inns

Some of the most difficult structural works involved the widening of overbridges on the former A80. The most complex of these was arguably the bridge at the Old Inns junction where upgraded slip roads and the addition of hard shoulders necessitated a substantial widening and the rebuilding of the parapets. This required the provision of substantial falsework under the bridge to protect traffic passing underneath, and the use of hydro-demolition in the areas where the additional structural elements were being keyed into the old structure. Similar treatment was necessary on the Dullatur Road bridge, but in this case, there was no junction involved.