Work on an area of Appin Road identified as a crash hot spot will start next week.
The work will take place on a 1.6-kilometre stretch of the road, to the east of Appin and towards the end of the eastbound overtaking lanes.
A 2014 Roads and Maritime Services report identified the area as one of four crash clusters.
In the five years to 2014 the report found there were seven crashes, including one fatality.
There were more crashes at each of the other three clusters.
Roads and Maritime Services will spend $885,000 to widen the centre lines at this location and also increase the width of the road shoulders.
Work will start on Sunday night, between 7pm and 5am, with no work on Monday.
On Tuesday stage one of the work from 7am to 5pm will take place for three weeks.
One eastbound lane will be closed during the first stage of the work, with one lane remaining open in each direction.
Stage two will be carried out at night from December 4.
A 40km/h speed limit will be in place while the work is carried out.