Canberrans heading to the coast will face at least a five-and-a-half hour extension on their trips when Transport for NSW closes the Kings Highway over the Clyde Mountain in coming months.
The road is expected to be closed during work hours for four days a week for up to two and half months.
Workers will remove unstable trees from the roadside beginning on August 30, and work is expected to continue until at least the middle of November.
Transport for NSW's regional director for the south, Sam Knight, said the highway would be closed from River Forest Road to Misty Mountain Road from Monday to Thursday between 8am and 4pm.
"An arborist report identified approximately 400 high-risk trees on the Clyde Mountain section of the highway which were badly burnt in the 2019-20 bushfires," she said.
"These trees have become more unstable due to subsequent storms and flooding, and will be removed as they pose a safety risk to road users.
"This work must be carried out under full road closure of the Kings Highway during the day as there would be an unacceptable safety risk if the work was carried out at night."
The road will be open from 4pm to 8am from Monday to Thursday, but will also remain open on Fridays, Saturdays, and Sundays, as well as public holidays and school holidays to ensure high volumes of traffic aren't negatively affected.
Ms Knight encouraged drivers to plan ahead.
"The benefits of an eight-hour full road closure include work being completed more efficiently and in a shorter timeframe," she said.
"Closure times have been determined in consultation with Eurobodalla Shire Council and aim to balance minimising disruption to motorists with the need to safely and efficiently carry out the work.
"Alternative routes will be available via the state and regional road network, and Transport for NSW encourages motorists to travel outside of the closure times or plan their journeys in advance."
The alternate northern route would involve heading north on the Hume Highway until the Picton Road turnoff, a trip that could add up to seven-and-a-half hours.
The alternate southern route is via the Kings Highway, Monaro Highway, Snowy Mountains Highway and Princes Highway, and would add about five-and-a-half hours.