Transmission Gully, the new $1.25 billion motorway out of Wellington, will not be open by Christmas.

Waka Kotahi NZ Transport Agency confirmed in a statement this morning the builder has run out of time to complete safety, quality assurance, and consent tasks for the road to open in time for the holidays.

It's the latest in a string of delays for the troubled road that has become somewhat of a nightmare for all parties involved.

The four-lane motorway is being built through a public-private partnership (PPP), the Wellington Gateway Partnership (WGP), with CPB Contractors and HEB Construction subcontracted to carry out the design and construction.

Waka Kotahi chairman Sir Brian Roche said it was extremely disappointing.

"Like everyone else, we are frustrated by the delays and lack of certainty about when the road will be able to open and while we can't yet say when it will be, we can be certain that it won't be this year.

"It may in fact be some time before all the safety and quality assurance tests required in the contract are met."

Waka Kotahi chairman Sir Brian Roche. Photo / Mark Mitchell

In early November Waka Kotahi had still not given up hope that Transmission Gully would open this year, but it has become increasingly clear it was going to take a Christmas miracle for that to happen.

Waka Kotahi transport services general manager Brett Gliddon said achieving a pre-Christmas opening was dependent on the road's builder meeting contractually agreed requirements to ensure the road is safe for motorists and completed to a high standard.

There are 100 safety and quality assurance tests that need to be met before the road can safely and legally open.

But as of December 10, just 41 final test submissions had been received from the builder.

Of those, only 34 have been accepted by an independent reviewer as meeting the required specifications.

Meanwhile, there are also 45 consent tasks that need to be completed for the road to open.

As of December 3, there were 17 completed, 26 under way, and two not yet started.

"Based on the information we have, and advice from the Independent Reviewer, we do not have sufficient assurance that all the tasks still needing to be finished to ensure the road is safe and reliable on an enduring basis, can be completed between now and Christmas", Gliddon said.

"Waka Kotahi has been working with WGP and CPB HEB to determine how best to address some of the outstanding issues in order to get the road open to the public as quickly as possible while ensuring the enduring safety and quality of the road is not compromised", he said.

An update will be provided to the public once those discussions have concluded and there was a clear way forward, Gliddon said.

The road was meant to open on September 27, which was itself a delay to account for the fallout from the Covid-19 lockdown in 2020.

The project was again hampered by the pandemic when the country went back into lockdown this year in August, although Waka Kotahi considers there was already significant risk the builder was not going to meet the September deadline prior to the Delta outbreak.

Commercial discussions are continuing to determine how much of the delay is due to the recent lockdown and lower alert level restrictions, and the resulting financial implications of this.

Transmission Gully is New Zealand's first transport infrastructure project being delivered under a PPP.