Roads and Maritime Services crews will begin safety upgrades on Farnell Avenue and Audley Road in the Royal National Park next week.
Work on the $470,000 project will begin on Monday and is expected to take a month.
Work will be carried out from 10am-3pm on weekdays with some 8pm-5am work on Sunday to Friday (weather permitting).
Partial road closures will be in place and delays are expected.
The work will include the installation of one-metre wide road shoulders, non-skid horizontal lines to warn drivers on approach to curves, curve warning signs, speed advisory signs and new safety barriers.
There were five head-on crashes and four off-road crashes on these roads in the five years up to December 2011, which resulted in one death.