The work will take place on the Glen Garry to Dalwhinnie and Dalwhinnie to Crubenmore schemes totalling nearly 13 miles.
The work is expected to be completed in approximately three months.
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Michael Matheson, Cabinet Secretary for Transport, Infrastructure and Connectivity said: "The A9 Dualling programme between Perth and Inverness is one of the largest and most challenging infrastructure projects in Scotland's history.
"With ground investigation works already underway on a number of sections of the route, these latest works starting next month will help inform the design work for the neighbouring schemes stretching from Glen Garry to Crubenmore."
