TARGETS for cutting traffic growth have been dropped by the Scottish Government, which is now planning for up to 20% more journeys on Scotland's roads by 2020 and more rush-hour bottlenecks, The Herald has learned.

The policy shift has sparked an angry reaction from environmental groups, who have accused the SNP of watering down its commitment to reducing greenhouse gas emissions and harmful pollutants from road transport.

Environmental charity WWF, which highlighted the policy shift, accused Government ministers of abandoning a commitment made by the previous Scottish Executive.

Dan Barlow, head of policy at the charity, said: "It is very disappointing that the SNP Government seems to have abandoned a previous government commitment to stabilise traffic levels and instead is planning for traffic growth of up to 20%.

"Increasing the number of cars on Scotland's roads will jeopardise our ability to meet the 2020 climate emissions target and only add to our air pollution problem."

Much of the traffic increase over recent years is thought to be due to the expansion of Scotland's motorway network – traffic on major roads has doubled between 1983 and 2010.

The recent completion of the M74 extension in Glasgow and M80 upgrade between Glasgow and Stirling is expected to fuel this growth, as will the planned construction of the Aberdeen ring-road and completion of the M8 between Glasgow and Edinburgh.

However, the Scottish Government denied it had made a U-turn, claiming there had been a "huge change" in the long-term outlook for public finances and global economic conditions, which required a more "sophisticated" approach to the problem of tackling traffic growth.

An "aspirational target" of stabilising traffic volumes at 2001 levels by 2021 was set by the previous Labour/LibDem coalition in 2006 and inherited by the SNP when it won power in 2007. Traffic levels have subsequently declined slightly from a peak of nearly 45,000 vehicle kilometres per year, largely as a result of the UK's economic downturn.

But the Scottish Government's Infrastructure Investment Plan, published in December, predicts that this dip will be temporary and that traffic volumes will increase over the next decade as the economy recovers.

It claims the "best evidence" suggests there will be 15% to 20% more vehicle kilometres per year by 2020, adding to the problems for millions of motorists driving into Scotland's cities.

"Making better use of our networks is critical to addressing the climate change targets we face," the document states.

"The best evidence suggests that the demand for travel will increase by 2020, linked to the underlying growth of the Scottish economy of around 2% per annum.

"This is likely to result in a 15% to 20% growth in vehicle kilometres by 2020.

"There is little evidence of a sustained downturn in the demand to travel, with the result that pressure on networks in urban centres will increase, with congestion at peak periods."

Environmental groups are still reeling from last September's Scottish Budget, which saw investment in "active" forms of travel such as walking and cycling slashed in favour of spending on major transport infrastructure projects.

Sustainable transport charities Sustrans and Transform Scotland have both claimed that the cuts will make it harder for Scotland to achieve targets for reducing car travel and encouraging a switch to public transport and cycling.

It emerged last month that roadside pollution levels in Aberdeen, Edinburgh, Glasgow, Dundee and Perth are in breach of safety limits agreed by the European Union, according to provisional 2011 monitoring data.

A Scottish Government spokeswoman said: "We have set a vision which ensures our roads are as efficient as possible, complements the work under way to develop low-carbon vehicle technology, promotes active travel choices and encourages a modal shift to public transport."