Amey, BEAR Scotland, a joint venture between Graham and WSP and the Transerve consortium including Balfour Beatty and Mouchel are chasing a £175m contract to maintain 1,300-km of roads in north west Scotland.
Tenders are due back by the end of January to Transport Scotland for the deal, known as the North West Unit of the 4G Term Contract, and a contractor is expected to be appointed before next April.
The initial contract will run for five years and is expected to see spending of between £27.5m and £35m a year.
The contract will also include an option to extend by a further five years.
Major roads covered by the deal include the M9/A9 between Stirling and Thurso, the A82 from Dalnotter to Inverness and the A83 from Tarbet to Lochgilphead and Kennacraig.
The winning bidder will also be responsible for maintaining sections of the A85, the A86 from Spean Bridge to Kingussie and sections of other trunk roads including the A87, the A99, the A830 from Fort William to Mallaig, the A835/A893, the A887 and the A889.