Last-minute problems with Auckland's Waterview Connection have held up its grand-opening for another three months.
The country's largest road tunnel project was due to open in April after five years of construction.
However, Brett Gliddon from the New Zealand Transport Agency (NZTA) says there have been minor problems with the deluge and ventilation systems.
The NZTA says these faults need to be fixed so the tunnel can operate safely.
The agency admits this will be frustrating for motorists, but says safety must be the priority.