Lawrence Hargrave Drive will close for eight straight weeks from June to carry out slope stabilisation work.
Plans to close the road at Stanwell Park for two four-week periods caused widespread opposition when it was first announced in July last year.
The backlash led Transport for NSW to step back and carry out further consultation with the community, offering four options for the work to be carried out.
Two of the four would see the road opened for some periods of the day, but would also result in the work taking longer to complete.
Transport for NSW Regional Director South Sam Knight said the preferred option that arose out of the consultation was to carry it out in one one eight-week block starting on Tuesday June 9.
A Transport for NSW consultation report said 720 responses were received and 33 per cent chose the eight-week closure.
Though 31 per cent opted for one of the other options that would see the road opened in the early morning and after school finished.
"Focusing the work in one eight-week block in winter is more efficient and will see most noisy activities completed during daylight hours," Ms Knight said.
"This work is essential to keep the road safe and open to traffic well into the future.
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"Transport for NSW has taken into account community priorities including avoiding work in the busy summer months, minimising night work disruptions and impact to businesses, and carrying out the work as quickly as possible."
The work will see Lawrence Hargrave Drive closed between Otford Road and Chellow Dene Avenue at Stanwell Park.
Emergency services have confirmed they will maintain a level of service while this work is completed and the road is closed.
The closure period will include the two-week July school holidays.
People in the northern suburbs who used Lawrence Hargrave Drive to travel to and from work in Sydney will now need to travel south through Thirroul and use Bulli Pass.
Stanwell Park residents will be able to catch additional express train services from Stanwell Park station while this work is carried out.
During the closure, Transport for NSW is looking to run shuttle buses to connect northern suburbs residents to train services in Stanwell Park and Helensburgh along with selected schools.
People are asked to visit the rms.gov.au website to lodge their interest in using a shuttle.
Transport for NSW will be running a community drop-in session in the coming months to keep the community up to date on details of the work, including shuttle bus and train timetables and maps.
The work to stabilise the site will use mesh and steel bars up to 13 metres long and will be installed along a one-kilometre stretch of Lawrence Hargrave Drive at Stanwell Park.
A concrete retaining wall will also be built to reinforce the slope.