Transmission Gully was meant to open today but has been delayed again, so the Herald has created an interactive map to fly you through the $1.25 billion road instead.

Waka Kotahi NZTA remains tight-lipped about ongoing negotiations over a new opening date for the 27-kilometre motorway out of Wellington.

The troubled road 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.

Its opening has been delayed due to the current Covid-19 Delta outbreak.

When it does eventually open, Transmission Gully will become State Highway 1 and will be the main route in and out of Wellington.

The road is designed to be safer and more reliable for motorists. It will also be better able to resist and recover from earthquakes and storms.

It's considered to be one of the most significant pieces of new road construction in New Zealand.

Last year, Wellingtonians were told Transmission Gully would be open by Christmas 2020.

Now a question mark hangs over whether it will even be open by Christmas 2021.

The builder was going to be liable for $250,000-a-day in damages if the road didn't open on time.

Furthermore, $7.5 million of a $145.5m settlement covering the cost impacts of Covid-19 was not going to be paid out if the road was late.

But Covid-19 alert levels 3 and 4 are considered a force majeure event. This relieves an affected party from contractual obligations because of an event outside of its control.

Waka Kotahi transport services general manager Brett Gliddon has said the transport agency is working with the builder to understand the full effects of the lockdown and restrictions on the project, and confirm a new opening date.

"We know that people are keen to see the road open as soon as possible, and everyone is working as fast as they can to get the road open to the public."

Transport Minister Michael Wood has also said the length of a lockdown doesn't necessarily directly equate to the length of the resulting delay.

"There are a whole lot of complex factors which come into it. In terms of how you reassemble the labour force who might be spread across a range of different projects, the time that it takes to get different pieces of work under way, and that kind of thing."

WGP and Waka Kotahi will provide an update on a new opening date once the additional time required to complete the road for public use has been agreed.

Waka Kotahi has advised there will be no further comment until then.