The intersection of Mangorei Road and Northgate continues to have major road works and repairs being undertaken, a month after the new road was officially opened.

A month after its official opening the much anticipated Vickers to City upgrade remains unfinished and cracks in the surface in one section won't be fixed for months.

The project, which was touted as the solution to New Plymouth's traffic woes, began in 2014 with a $16 million budget but when it was opened last month the cost had blown out to $24 million.

Construction at the intersection of Northgate and Mangorei Rd is ongoing and continues to cause long delays for commuters while a section of the south bound road, near the intersection with Bridle St, is riddled with potholes.

New Zealand Transport Agency highway manager Ross I'Anson said the area near Bridle St required more work on the road surface in order to provide a long term solution.

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"This work will take place over the next summer construction period, which starts in November 2016," I'Anson said.

New Plymouth District Council deputy mayor Heather Dodunski, who had previously described the finished product as sub-standard, said she had noticed the delays in finishing the work at Mangorei Rd and the inferior surface of the road.

"We still don't seem to have that quality surface that we had expected," Dodunski said.

"I am concerned and it's certainly taking a bit longer than what any of us had hoped for."

While Dodunski said she was disappointed the project had not been fully completed to the high standard expected there may be good reasons.

"We're grateful that they found the extra money to have the job done properly," she said.

"We'll all be keeping an eye on it to make sure we get that quality finished product."

Councillor Gordon Brown, who uses Mangorei Rd daily, said he had had several near misses at the intersection, which he called a shambles, due to poor road marking.

"It's more dangerous than it has ever been for those of us that have to use the Mangorei Rd intersection at Northgate," Brown said.

"They need to fix it asap."

Brown said he wasn't calling for heads to roll yet.

"They should be at least on the chopping block with the axe poised."

Councillor Colin Johnston, who makes the commute from Waitara to New Plymouth daily, said he was "bloody annoyed" with the state of the road.

"It should have been finished well and truly before they opened it up," Johnston said.

"I'm shocked that they haven't been able to get that right."

He described the section of road at the intersection with Bridle Rd as shocking.

"I can't understand why they've used the old road and the new road they way that they have.

"With the amount of money that they've spent on it, it's not good enough."

Johnston said he was also concerned by the additional cost occurred.

"There's no excuses that they should have been over budget anyway."

Councillor Richard Handley, who uses the Mangorei Rd intersection regularly, said the ongoing work added a layer of risk to motorists.

"I understand that there's a significant cost over run and there is still parts that need to be completed but it is their responsibility to do it to standard and get it done," he said.

I'Anson said the project was not over budget as the $16 million was a base estimate and a variation in the final costs were usual for a project of this size in a complex environment.

"We increased the scope and cost significantly, extending the four laning as well as including additional pavement LED lighting and retaining walls.

"The final result is a better, safer and more resilient road, which will be easier to maintain, resulting in less disruption for the local community."

He said the ongoing work at the Mangorei Rd intersection involved service relocations and testing of underground utilities including water mains.

"Ensuring traffic flows freely has been a priority for us, although undertaking the work in a live traffic environment is a challenge.

"When the utilities work is complete, the intersection will be tidied up and re-surfaced."

I'Anson said depending on the weather the work was expected to be finished by the middle of August and the NZTA appreciated motorists' ongoing patience while the work was carried out.