In a move to keep them off the road, a koala grid will be installed as part of the Picton Road fencing already in place.
A trench will be cut across Alkoomie Place - near the Picton Road intersection - to put the grid in place.
"The uneven surface of the grid and the gaps between the grid and the road surface deters koalas from crossing," a Transport for NSW spokeswoman said.
It works much like a cattle grid, with vehicles still being able to cross over it.
The grid will work in conjunction with the nine kilometres of 1.6-metre high koala fencing being installed along Picton Road at the marsupial "hot spots" near Allens and Cascade creeks.
"The fencing will provide protection for areas of critical koala habitat and where koalas are known to cross Picton Road, helping reduce the incidence of koalas being hit by vehicles," the spokeswoman said.
A koala underpass was also put in place below Picton Road in December last year.
Work on installing the koala grid began on Friday and will continue for a week, between the hours of 9am and 3pm.
A Transport for NSW spokeswoman said there would be "intermittent delays" to traffic in Alkoomie Place while the work is carried out.