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Up the junction

MI widening - Widening of one of Britain's most congested stretches of motorway is racing ahead. Jon Young reports from the M1

In 1989 demonstrators demolished the Berlin Wall, Band Aid made a second attempt to relieve poverty in Africa and the Highways Agency initiated plans to tackle one of Britain's most congested stretches of motorway.

Some 18 years later, after a pleasantly Band Aid-free Christmas, a Balfour Beatty and Skanska joint venture (BBSJV) is knee deep in the largest road scheme under way in Britain.

Widening and remodelling the M1 junction 6A to 10 will help alleviate the strain that 160,000 vehicles a day are putting on the three-lane carriageway and prepare it for the 200,000 vehicles a day expected by 2023.

Over the 194-week contract joint venture engineering and design manager Kieran McGibbon says that the team will remodel three interchanges, demolish and rebuild seven overbridges and widen 11 underbridges. It will add a fourth lane along much of the route (part of the route is already at four lanes) and reduce the number of accidents by constructing new local distributor roads.

All this for the princely sum of £298M.

McGibbon explains that this stretch of motorway is more heavily congested than the section of the M25 around Heathrow that Balfour Beatty widened in a joint venture with Costain in 2005. It also has a greater amount of heavy goods vehicles as it is the main route north from London and the Channel ports.

He adds that, aside from safety, minimising disruption is the top priority in order to meet the government's Public Service Agreement targets for journey time reliability. The design by Atkins and the construction method was chosen to this end.

The Early Contractor Involvement contract was awarded to BBSJV in March 2005 and construction kicked off a year later. The first of seven bridge demolitions was a milestone in the project in late November last year (NCE 23 November 2006). It is hoped that the project will be nished by December 2008.

Of the 17.5km of motorway being transformed, two major challenges stand above the rest.

Remodelling junctions 8 and 10 relies on a carefully planned schedule to stop the motorway grinding to a halt, explains McGibbon.

Junction 8 currently feeds trafc between Hemel Hempstead, the east-west M10 and the north-south M1 via a tight loop to the south east of the M1. By widening the loop and ipping it to the north and constructing a new distributor road it is hoped that the high accident rate at this junction can be reduced with little disruption to trafc (see box).

Junction 10 feeds traffic between the M1 and Luton Airport. Construction of a new interchange around the old was deemed the best plan of action as it will allow the existing interchange to function until the new is in place and complete.

A 40mph speed limit will be imposed throughout the works as teams will be working close to live carriageways.

Junction 10 is being tackled rst and includes the construction of two new interchange overbridges, extending 54m across the M1 in two spans of steel composite construction.

Construction of new northbound and southbound on and off slip roads, including dedicated 'free-ow' connector roads on and off the M1 southbound at junction 10 for Luton, will drastically improve the flow of traffic through the interchange.

Church Road underbridge to the north of junction 10 will be widened to accommodate the northbound on slip and southbound off slips respectively.

The construction of the new Slip End overbridge, which was the first bridge in the project to be demolished, is under way.

The new bridge will span the M1 to facilitate the motorway widening below.

When completed, traffic will be diverted onto the new infrastructure to allow the removal of the existing interchange, including the demolition of the two existing overbridges, with minimal disruption to traffic flows.

Junction 8 A new interchange will be constructed marginally north of the existing one at junction 8. Work includes the construction of a new four-span steel composite overbridge extending 104m across the M1.

New 'collector distributor roads' will be constructed parallel to the M1, south of junction 8 to collect and distribute traffic on to and off the M1, from and on to the M10.

'The new road layout will signicantly reduce the number of traffic weaving movements where the M10 presently merges with the M1 and is expected to reduce the number of accidents that typically occur at this location, ' explains McGibbon.

He adds: 'Queuing on the M1 on the northbound carriageway between the M10 merge and the A414 exit for Hemel Hempstead will also be eliminated, improving traffic flows and road safety.' As with the junction 10 interchange, all of the new construction is being carried out around or off line from the existing infrastructure in order that disruption to traffic flows is minimised.

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