The decision to bring forward the work follows a move to divide stretches of the route between Perth and Inverness earmarked for improvement.
Contractors will now be able to proceed earlier on sections where preparations for the upgrade can be done more quickly than the rest of the route.
The first stretches to undergo improvements, a year earlier than planned, will be the 6.5 miles between Pitagowan to Glen Garry, the 5.2miles from Dalwhinnie to Crubenmore, and 5.7 miles from Tomatin to Moy.
Draft proposals have also been published for one of the busiest sections of the A9 near six-mile stretch between Luncarty to the Pass of Birnam near Dunkeld, Perthshire. Work on the 4.5-mile stretch between Kincraig and Dalraddy is already due to start in 2015/16 and be completed in 2017.
A new landscape policy has also been announced for the project to protect the environment.
Transport minister Keith Brown said: "We have pledged to bring forward elements of the scheme wherever we can and we are delivering on that.
"As a result of the detailed survey work that has been going on along A9 between Perth and Inverness, we are providing further details which will see the programme divided into 12 distinct schemes from the original nine, allowing three new sections of the route, totalling 17.46 miles of upgraded road, to be accelerated through the complex design and legal process.
He said there was 82 miles to be dualled between Perth and Inverness and these schemes helped to meet the Scottish Government's pledge to complete more than half of the entire upgrading by 2022 and it all by 2025.
Nick Halfhide, head of operations at Scottish Natural Heritage, said of the new proposals for the road: "The A9 passes through many sensitive areas for wildlife and their habitats, which will clearly need to be taken into account in the dualling project."