A9 Inverness to Perth carriageway upgrade to start early
A £3bn programme of work to make the A9 dual carriageway all the way from Inverness to Perth will start early, the Scottish government has said.
The improvements will begin by 2015-16, rather than 2017-18, with an enhancement of the Kincraig to Dalraddy overtaking lane south of Aviemore.
There are about 80 miles (128.7km) of single carriageway between the cities.
The Lib Dems said it would be a "mammoth task". Labour said the SNP were "re-annnouncing" old news.
The Scottish Conservatives said the road needed to be fit for the 21st Century.
The Scottish government had previously said that it planned to spend £3bn on upgrading the road from Inverness to Perth.
Infrastructure and Capital Investment Secretary Alex Neil has announced that the programme of work will now start earlier than previously planned.
He said: "The A9 is the longest trunk road in Scotland and we have always said that delivery by 2025 was challenging but achievable.
"I'm especially delighted to announce we are advancing the Kincraig-Dalraddy section to full dualling and doing so early.
"This development of the existing scheme will now provide overtaking opportunities in both directions, breaking up platooning and reducing driver frustration.
"Not only are we adding these additional safety benefits, we are also getting underway two years earlier than previously expected."
So far, the government has spent £50m on improving parts of the 113.4 mile (182.5km) stretch between Inverness and Perth.
Seven sections of single carriageway amounting to 80 miles (128.7km) remain to be upgraded to dual carriageway.
They are Luncarty to Pass of Birnam, Pass of Birnam to Ballinluig, Pitlochry to Killiecrankie, Killicranky to Glen Garry, Glen Garry to Crubenmore, Crubenmore to Slochd and Tomatin to Moy.
Labour MSP Richard Baker said the SNP were "simply re-announcing" what was already known about the programme and the work would still not be completed until 2025.
Scottish Liberal Democrat MSP Jim Hume said completing the project would be a "mammoth task" that was necessary and should be done as quickly as possible.
SNP MSP Dave Thompson has welcomed the plan to change the Kincraig overtaking lane to dual carriageway.
The A9's entire length runs from Thurso in Caithness to Bridge of Allan, near Stirling.
North of Inverness, £220,000 is to be spent on designing improvements to Berriedale Braes in Caithness .
Highland Council, transport body Hitrans, Transport Scotland and the Nuclear Decommissioning Authority, through its involvement with the Dounreay nuclear site, will fund the design work.
Where the money will come from to cover the £2.3m construction project has still to be identified.
Figures made public earlier this month by Tory MSP Murdo Fraser suggest more people died on the A9 between 2006 and 2010 than on any other Scottish route.
Mr Fraser, MSP for Mid Scotland and Fife, had asked Transport Minister Keith Brown for figures on the 20 roads with the highest number of accidents and fatalities.
There were 67 fatalities and 1,206 accidents involving injuries on the A9 between 2006 and 2010.
Following the latest government announcement on the road, Mr Fraser said: "No one expects the A9 to be dualled overnight but the sooner we start dualling the road, the sooner we will see a road fit for the 21st Century.
"We now need to have the ambition to bring forward the completion date as 2025 is too long to wait."