Motorists on the A9 can expect months of delays as the dualling programme gathers pace on two stretches.
Traffic restrictions will be put in place to enable vital ground investigations to be carried out on the carriageway.
The work will take place between Kincraig and Dalraddy the first section to be dualled and between Birnam and the Tay Crossing (Jubilee Bridge), starting on Wednesday October 1.
It is anticipated that the works between Kincraig and Dalraddy will finish on October 12.
The work between Birnam and Tay Crossing, one of the most challenging parts of the route, is expected to take around 15 weeks and will not finish until early January 2015.
No works will take place during the two-week festive period.
The traffic management arrangements will include relatively short contraflow sections controlled by temporary traffic signals.
The contraflow sections will be moved along the length of each scheme as the work progresses.
The contractors for both sets of works have pledged to monitor the operation of their traffic management to ensure that delays are kept to a minimum and that any incidents on site are dealt with quickly.
A spokesperson for Transport Scotland said: “We apologise for any inconvenience caused by the works and thanks road users and local communities for their patience over the next four months.