[4] A good portion of the highway serves as a gateway from Melbourne to Phillip Island.

Bass Highway commences at the interchange with South Gippsland Highway at Lang Lang and heads in a southerly direction as a four-lane, dual-carriageway road along the eastern coast of Western Port Bay, through Grantville, to the turn-off to Phillip Island) at Bass.

The passing of the Transport Act of 1983[10] updated the definition of State Highways; the highway was extended east one last time from Inverloch to Leongatha in December 1990,[11] subsuming the original declaration of Inverloch-Leongatha Road as a Main Road and completing its present-day alignment at this stage.

With Victoria's conversion to the newer alphanumeric system in the late 1990s, this was replaced by route M420 between Lang Lang and Grantville, A420 between Grantville and the Phillip Island turn-off at Anderson, and B460 between Anderson and Leongatha.

[4] A project to duplicate Bass Highway from Lang Lang to Bass (east of Phillip Island) commenced in the late 1990s, addressing the high traffic demand of the route and recent crash history.