The Transport Agency has released a shortlist of four roads to replace the Manawatu Gorge road - each of them taking at least five years to finish and costing at least $300 million dollars.

Photo: NZTA

The gorge road on State Highway 3 connects Palmerston North to the east coast of the North Island and has been out of action since April after a series of slips.

Many parts of the gorge are unstable and it is no longer viewed as a viable long-term route. The number of crashes increased after the gorge closure, as traffic was forced to go via the Saddle Road.

There are many unstable areas through that road and it is no longer considered a safe long-term option.

The Transport Agency today released its shortlist of four alternative state highways to replace it.

Any of the proposals would cost at least $300 million, and take at least five years to complete.

Check out an interactive map of the options to replace the gorge road:

The first is a new road across the Ruahine Range, north of the Saddle Road, which is currently acting as an alternative to State Highway 3.

This would cost between $350m and $400m, and would take five to six years to complete.

The second is an upgrade of the Saddle Road, which would bring it up to state highway standard.

This would cost between $300m-$400 million, and would also take five to six years.

The third is a new road across the Ruahine Range, south of the Saddle Road, at a cost of $350m-$450m, which would take five to six years to finish.

The fourth and final option is a new route south of the Manawatu Gorge, costing between $450m- $550m, that would take six to seven years to complete.

Five alternatives were ruled out by the agency for a variety of reasons including cost, ecological impact, and difficulties getting resource consent approved.

Many residents at a meeting last month were unimpressed by the 13 possible options, which included a viaduct, tunnels, a new southern route and an upgraded Saddle Road.

A major slip above the Kerry's Wall rock face was deemed highly unstable by geotechnical engineers earlier this year

Public feedback on the shortlist is open until 25 October, and a preferred option will be announced in December.