Ministers today insisted they were remained on track to complete the remaining 75 miles of A9 dualling in seven years time as they unveiled plans for the next section.
Details were announced for the stretch north from Killiecrankie to link with an existing dual carriageway section in Glen Garry, which leads to the Drumochter summit.
The Scottish Government's Transport Scotland agency, which is in charge of the project, described it as "another milestone" in their "ambitious" £3 billion plans, due to be finished by 2025.
So far, only five miles of the 80-mile Perth-Inverness project have been completed with the opening of the stretch between Kincraig and Dalraddy, south of Aviemore in September.
Work is expected to start on the next section, to extend the existing Perth dual carriageway north from Luncarty to the Pass of Birnham, near Dunkeld, early next year.
Draft orders and an "environmental statement" showing the line of the Killiecrankie-Glen Garry section have been published.
They include a new junction with slip roads at the House of Bruar shopping complex, north of Blair Atholl,
There is also a new bridge over the River Garry and the "construction challenge" of extensive rock outcrops.
Exhibitions of the route will be held from 1-9pm on Wednesday 13 December in Killiecrankie Village Hall and 1-9pm on Thursday 14 December in Blair Atholl Village Hall.
Economy secretary Keith Brown said: “Our ambitious programme to dual the A9 between Perth and Inverness will bring many benefits for road users, communities and businesses who live along or use this important route between central Scotland and the Highlands and Islands.
“The work is continuing across the route and road users are already benefiting from the new dualled stretch between Kincraig and Dalraddy.
"We expect to get work underway on the next section to be dualled between Luncarty and Pass of Birnam early next year.
“At the same time, design work on the other sections to be dualled is well advanced.
"Today marks a further significant milestone in our plans, with draft orders being published for a well-used 13 mile stretch of the road between Killiecrankie and Glen Garry.
“This is just the start, as we expect to publish draft orders for further dualling projects over the coming months."
A Transport Scotland spokesperson added: “We are committed to dualling the A9 between Perth and Inverness by 2025, one of the biggest transport infrastructure projects in Scotland's history.
“The work is progressing apace, with the Kincraig to Dalraddy section now open to traffic and bidders being sought for the Luncarty to Pass of Birnam section.
"In addition, the design work on the remaining schemes of the dualling programme is well underway with over 90 per cent of the dualling programme having now reached preferred route status.
"We have today published the draft orders for the stretch between Killiecrankie and Glen Garry with more to come over the coming months.”
However, Scottish Conservatives transport spokesman Jamie Greene said: “With only five of the 80 miles of this project completed ,it remains difficult to see how this will finished on time at this rate.
"We have also been contacted by a number of farmers who are deeply unhappy at the communication between the contractors, Transport Scotland and those affected by the construction – there remain live issues on this project.
“Given recent problems with the Queensferry Crossing, I hope the Scottish Government is being fully open and honest with the public about how realistic its opening targets are."
Scottish Labour transport spokesman Neil Bibby MSP said: "Transport Scotland have known about these faults for months and they have chosen to keep that information from the public.
"Road users found out about carriageway closures at the last minute and officials have confirmed that there are more closures to come.
"The SNP transport minister must give a full explanation and account for his handling of the project.
"Either the SNP knew about this fault and choose to keep it quiet or they didn't, which demonstrates yet again their gross mismanagement of major infrastructure projects."