State Highway 3, south of Mokau, is on track to be re-opened tomorrow afternoon following a major slip on Sunday.

The New Zealand Transport Agency said the road should be opened to one lane by 1pm.

"We have been working today with abseilers to remove the last of the loose rock," NZTA spokeswoman Karen Boyt.

"Our geotechnical engineers have now advised us that the cliff face has stabilised sufficiently to allow contractors safely on site to clear the rocks and debris, and reinstate concrete barriers."

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The road would be under stop/go management after reopening and would initially have a speed limit of 30km/h.

NZTA warned because of this, motorists should expect minor delays.

"We anticipate that a number of people will want to travel on State Highway 3 once the road has been reopened, so we ask that motorists take this into account and are patient," Boyt said.

"We realise that this closure has had a big impact on many, including the Taranaki community, and the trucking industry.

"We would like to thank everyone for their on-going patience while we work to get this important route open again."

Once the road was re-opened, NZTA would begin investigating and designing a more permanent engineering solution to replace the wire mesh, Boyt said.

Until this section of SH3 opens again, motorists were asked to continue to use an alternative route via State Highway 1 or State Highway 4 via Whanganui, which will add approximately three and a half hours to the journey.

Other local road routes via Ohura and State Highway 43 were not suitable detours for SH3 traffic, NZTA said.

Transport Agency contractors have now cleared the slip at Tangarakau Gorge, State Highway 43.