The work is programmed to start in March and is expected to be on site for a period of 18 weeks.
Transport minister Humza Yousaf said: “We remain committed to upgrading the A82 between Tarbet and Inverarnan.
“These ground investigations due to get underway next month will provide the detailed information needed to help inform the development and assessment of the scheme’s design.
“We need to ensure that any future upgrade fits within the area’s outstanding landscape and environment and maintains the renowned beauty of the Loch Lomond and Trossachs National Park.
“The work we are doing along this vital route that connects the Highlands and Islands with the central belt will lead to improved road safety and journey time reliability and meet the needs of business, communities and visitors alike.”