Transmission Gully is open to the public, and there's already been a speeding ticket and a police car has found itself stuck.
After a ribbon-cutting ceremony yesterday, vehicles were allowed to start journeying up and down the 27km motorway early this morning.
But the new State Highway 1 has also left the old coastal route quiet.
Our reporter Jake McKee and cameraman Angus Dreaver went to check things out.
