State Highway 4 near Upokongaro finally has two lanes open to motorists as work to fully reseal the road continues.
The road has been one lane for most of the past six years, after a 2015 slip washed away a significant portion of the road.
The new portion opened on Monday, with previous road now bypassed and the temporary traffic lights switched off.
Work on the road has been controversial, with concerns ranging from the strength of the original repair, to criticism from business owners around the length of time the repair was taking.
Work was done in 2017 - almost two years after the original slip - to fill in parts of the road. This repair was short-lived, when around 3m of that fill slumped back into the river.