Balfour Beatty Civil Engineering Ltd has been awarded the £184.7m contract to dual the A9 between Tomatin and Moy.
The route between Perth and Inverness was retendered last September when Transport Scotland had to revise risks in the contract documents to attract new bidders.
Balfour Beatty Civil Engineering, John Graham Construction and Wills Bros Civil Engineering were originally shortlisted to bid for the 9.6km dualling job.
But after two pulled out, just one bid was submitted at a price much higher than the original budget of £115m.
The three firms who entered the retendered race were Balfour, John Graham and Sacyr UK Ltd.
Cabinet Secretary for Transport Fiona Hyslop said: “I am pleased to announce our intention to award the contract for Tomatin to Moy to Balfour Beatty. Once work starts on Tomatin to Moy, it will not stop until dualling between Perth and Inverness is complete.
“The award of this contract for A9 Dualling: Tomatin to Moy will start our rolling programme of construction to dual the A9 between Perth and Inverness and reinforces our steadfast commitment to deliver on our plan.
The contract follows the successful completion of advance works in 2021 and 2022, including the replacement of Lynebeg Underbridge on the Highland Main Line railway.
