Transport Scotland announced that the £40-£60 million contract for dualling more than 26 miles of the stretch of the A9 between Glengarry and Dalraddy is going to CH2MHill/Fairhurst.
The designers will start work on the middle section of the route next month, subject to the "mandatory standstill period" which gives other bidding parties the opportunity to lodge any objections. Three sections of the A9 between Perth and Inverness are now expected to be "shovel ready" for work to begin in 2017.
Most of the notoriously dangerous road is single carriageway, with the Scottish Government already having pledged to upgrade it to dual carriageway by 2025, with a £3 billion project to convert 80 miles of roadway.
Transport Minister Keith Brown said the appointment of the first design consultancy marked another signif-icant milestone in the Government's commitment to the project.