The £205m scheme will upgrade 6.4km of single carriageway to dual standard, including nine new bridges.

These include a substantial new crossing of the River Tummel alongside the existing Tummel Bridge, a new bridge alongside the existing Clunie Bridge over Loch Faskally, and a new rail bridge over the Highland Mainline Railway.

The Pitlochry to Killiecrankie section will be the third contract to use Transport Scotland’s revised NEC4 form featuring a carbon reduction fund to incentivise lower-carbon construction.

Transport secretary Fiona Hyslop said: “We expect to award this contract in Autumn next year and when construction is complete for this section it is anticipated that almost 50% of the A9 between Perth and Inverness will be dualled, demonstrating this Government’s commitment to complete this vital infrastructure improvement.”