Work on the "missing link" in Scotland's motorway network will finally begin within weeks.

Specialist teams of archeologists will begin site investigations and mitigation works along the route of the M74 extension in July in advance of the construction work, scheduled to begin in spring 2008.

A number of urban, industrial and brownfield sites on and alongside the route will be excavated, from Cambuslang in South Lanarkshire to the Kingston Bridge in Glasgow.

The archaeological proposals also include a full programme of public information, including an exhibition of the social history and a compilation of historic accounts relating to sites along the M74 completion corridor.

Glasgow City Council, the main partner in the project, is expected to approve a £5m contract for the advance archaeological works this week in the first meeting of the executive committee of the new administration.

The works should also allay concerns that the entire project could be under threat as the result of a coalition deal between the SNP and Green Party. The Greens, who have a Glasgow MSP, have been among the most vociferous campaigners against the extension and it had been thought the party would demand a commitment opposing the plan before agreeing to form a minority administration with the Nationalists.

However, the city council leader, Steven Purcell, who ahead of the election warned against meddling with the scheme, is understood to be satisfied the SNP-led executive will not oppose the extension.

After 40 years in the pipeline, the five-mile-long extension is currently at the tendering stage and is expected to cost somewhere between £375m and £500m.

The extension will be a three-lane motorway which will start near Carmyle and run to the M8 motorway just west of the Kingston Bridge. Expected to be completed by the end of 2010, it is designed to improve access along the entire Clyde corridor.

Backers believe the motorway will bring jobs to some of the most deprived areas of Scotland, including Glasgow's east end and parts of South Lanarkshire, and clear a major traffic log-jam at the Kingston Bridge.

Opponents cast doubts on claims of the road's economic benefits and warn of its environmental costs.

Several listed buildings and a number of non-listed buildings of some importance to industrial archaeology or social history will be demolished. Other sites earmarked for demolition include the Southcroft Park football ground, home to Rutherglen Glencairn junior football club.

The contract, valued at £4,947,268, is expected to be awarded to Edinburgh-based specialists Headland Archaeology on Wednesday.

The work will come as some relief to the business community, which has constantly championed the extension.

Glasgow Chamber of Commerce chief executive Dr Lesley Sawers said: "It is vital that we get traffic off the M8, recently found to be the most congested road in the UK, if Glasgow is to continue its economic success. The M74 extension will do this, and it is good news that it appears work is finally about to start."

Meanwhile, the £4m project to upgrade White Cart Viaduct, a bridge that forms part of the M8 motorway at Glasgow Airport, is set to finish today.

All traffic management restrictions, which have been causing tailbacks at the airport since January, will be lifted during the course of tonight.