Prime Minister Jacinda Ardern has officially opened Transmission Gully in a ribbon cutting ceremony on site this morning. 

The event marks a long awaited milestone for the new $1.25 billion motorway out of Wellington that has been bogged down with delays, construction defects and budget blowouts. 

Waka Kotahi NZ Transport Agency has instructed the contractor to open the road by the end of March. The road will open to traffic tomorrow. 

It means the four-lane road will be open in time for the Easter break, school holidays, and the return of tourists to New Zealand. 

Ardern said Transmission Gully will transform the Wellington region, making it quicker and safer for people and goods to travel through the lower North Island. 

"This road represents the largest Government investment in New Zealand's infrastructure in a generation. 

"It is an example of modern infrastructure that features the highest safety measures, treads lightly through the environment and is future-proofed for generations to come." 

Transmission Gully. Photo / Mark Mitchell 

The road will make journeys up to 15 minutes shorter for about 25,000 vehicles a day. 

It will improve productivity with people spending less time in cars and more time at work and with family, Ardern said. 

The Transmission Gully link roads, connecting the Porirua suburbs of Whitby and Waitangirua to the new motorway, were blessed in a ceremony yesterday. 

The 27 kilometre motorway will open two years later than it was orginially expected to. 

After a "huge amount of work" on the project over the summer, Waka Kotahi has said it's now confident the road has reached a stage where it is safe for public use. 

Its current cost of $1.25 billion will almost certainly balloon even further when negotiations over the fallout from last year's Covid-19 Delta outbreak have concluded. 

Transmission Gully 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. 

Infrastructure Minister Grant Robertson said the delay in getting the road open was because of National's "botched" PPP. 

"We have cleaned up their mess so commuters going in and out of Wellington will finally be able to use the alternative route." 

Robertson said the Government has asked the Infrastructure Commission Te Waihanga to revise New Zealand's PPP guidance to make sure any future partnerships don't encounter the same issues. 

Te Waihanga has already undertaken the first part of a review into Transmission Gully which found serious flaws at the planning stage of the project, undermining the successful completion of the motorway. 

A further review of the project will be undertaken now construction has been completed. 

"Wellingtonians deserve proper answers as to why this road took so long to be completed", Robertson said. 

Transport Minister Michael Wood said Transmission Gully is one of the most significant and complex new roading projects ever undertaken in New Zealand - but he undertsood the frustration over how long the road has taken. 

"This is an important piece of infrastructure it will be a a huge benefit to the Wellington region but everyone feels a bit of frustration over how long this has taken," he told MIke Hosking. 

He added the road was held up by a number of factors, including the Covid-19 pandemic and severe weather events. 

"Any reasonable person would expect would create some delays...There were particular factors related to PPP as well." 
The road is built over very challenging terrain and required "innovative environmental and construction techniques". 

"What was a series of steep valleys, criss-crossed with streams, and flanked by inaccessible hills, is now a state-of-the-art motorway that crosses gullies, passes over waterways and winds through pristine native bush. Around two and a half million native trees and plants were planted as part of the project." 

Transmission Gully has been built to the highest safety specifications and will provide a much safer route for road users, Wood said. 

Lives will be saved and many serious injuries prevented, he said. 

- Georgina Campbell, NZ Herald