TRAFFIC levels have eased significantly on a congested section of the M8 in Glasgow following the completion of the M74 extension in the summer.

But the number of cars travelling along other parts of the motorway network has increased, according to new figures obtained by The Herald.

The statistics show a reduction of more than 20,000 vehicles a day on the M8 between the Kingston Bridge and the junction with the M73 in July, the first month the new motorway was open, fulfilling a key target of the project.

Up to around 60,000 vehicles used the new five-mile section connecting the existing M74 at Fullarton with the M8 motorway in Glasgow city centre, a figure expected to increase as traffic volumes go up in winter.

At the same time, there were higher traffic levels on approaching motorway roads west of the new road, with around 12,000 more vehicles per day on the M8 and 6500 more on the M77, compared with July 2010.

However, at the busiest section of the M8, between junctions 16 and 15 in Glasgow city centre, there were 26,000 fewer vehicles in July. Figures from earlier in the year, before the M74 extension was opened, suggest there would have been around 5700 fewer vehicles anyway, a slump thought be caused by Britain’s continuing economic downturn.

The figures, based on automated weekday traffic counts with peak events such as traffic accidents filtered out, were given to The Herald following a Freedom of Information request.

They were seized upon by Transport Minister Keith Brown and Gordon Matheson, leader of Glasgow City Council, as proof the M74 project, which cost more than £650 million, had already delivered its core objectives.

Environmental groups who have opposed the motorway were sceptical, pointing to the increased traffic volumes as evidence it was having an overall negative impact by encouraging more people to drive.

Mr Brown said: “Initial figures clearly illustrate the M74 Completion, which opened eight months early and significantly under budget, has not only supported jobs during its construction phase but that its completion is ensuring easier access to business and employment.

“The new motorway was expected to reduce traffic on the M8 between Baillieston and Charing Cross by up to 20,000 vehicles per day. However, figures show the M74 Completion is, in fact, exceeding expectations by achieving reductions of up to 26,000 vehicles per day.

“We are also seeing initial journey-time savings of up to 19 minutes between Hamilton and Glasgow Airport during the peak periods for traffic using the new M74, while also effecting reductions of up to 28% in local traffic levels in nearby areas – again significantly better than expectations.”

Mr Matheson added: “Even at this early stage, this new road is meeting the targets that were set for it – and exceeding many.”

Selected figures released by Glasgow City Council show there has been 28% less traffic on local roads such as Rutherglen Main Street and Dalmarnock Road as more people opt to travel on the motorway network. However, figures for roads which were predicted to see increased traffic levels as a result of the new motorway have not been disclosed.

Dan Barlow, head of policy for environmental charity WWF Scotland, said the M74 extension reflected part of an unsustainable transport system.

He said: “Evidence has long shown building new roads generates new traffic. It is therefore no surprise to see significant vehicle levels on the new M74 and increased traffic on the surrounding motorway network which far outweigh the reductions seen on the M8 to the north of the city.

“As predicted, the overall impact of this traffic growth will be to increase Scotland’s climate emissions and lock us into an unsustainable transport system.”

The figures were welcomed by the Road Haulage Association, which said the M74 extension had reduced the number of bottlenecks on the motorway network.

Professor Stephen Glaister, director of the RAC Foundation, said: “These numbers suggest the M74 Completion lives up to expectations, however we will need many months worth of data to get the true picture, especially taking into account seasonal variations.”