Although traffic has started using the $3.5million-$4million roundabout, some sealing work will not be completed until spring.
Work on a pedestrian and cycle underpass next to the roundabout is scheduled to begin in the next few weeks.
The cost of the roundabout was met by Three Parks developer Willowridge Developments Ltd and the NZ Transport Agency will fund the underpass.
Helping Sir Tim cut the ribbon, on the count of three, are his grandchildren, Arthur (7), George (7), Katrina (10), Evie (10) and Genevieve (10) Wallis. Genevieve is partly obscured.