Auckland's new Waterview Tunnel will be closed for three nights this week, to test the fire safety and deluge system.
The northbound tunnel will be closed between 10pm and 5am for the next three nights, and there will be similar closures every three months from now on.
New Zealand Transport Agency system design manager Brett Gliddon said ongoing maintenance is crucial to keep the tunnel operating safely.
He said they will be testing electric equipment like smoke detectors, fire hydrants and deluge systems, as required under the manufacturers' guarantees and the building code.
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The opening of the tunnel on July 2 was delayed by three months due to issues with the deluge system.
Meanwhile, speeding tickets have started arriving in the mail box for people caught going over the 80km/h limit.
Police have not yet issued figures on how many people have been caught out.