Technical glitches delaying the country's biggest roading project are fixed, but no date has yet been set for the opening of Auckland's Waterview Tunnels.
The Transport Agency said it was doing a dry-run of the operating systems in the $1.4 billion twin-tunnels, ahead of a full commissioning process.
The twin tunnels, between Point Chevalier and Mount Roskill, will complete the western leg of the Western Ring Route around Auckland, providing a North-South motorway alternative to State Highway 1.
The agency remained coy about an opening date, though it was expected to be mid-year.
Auckland highways manager Brett Gliddon said teething troubles had been fixed in safety equipment.
He rejected speculation that there had been problems with the ability of the big air extractors to clear fumes when traffic slowed or stopped.
"The ventilation system is designed to take two tunnels fully congested with traffic if it comes to that, so we've got no concerns," he said.
"We did, through testing, have some issues with the jet fans which you turn on if there's a fire and smoke - which was one of the reasons we delayed the opening - but those have now been resolved."