A new route through the Manawatu Gorge won't be cheap or be completed in quick time.
A shortlist of four roads was released on Wednesday for the gorge, each having a price tag of at least $300 million, and the quickest taking five years to finish.
State Highway 3 through the gorge has been closed since large slips came down in April, and recent movement of rocks forced contractors out.
A shortlist of 13 roads has been whittled to four, after feedback was gathered from the community in recent weeks, NZTA spokesman Ross I'Anson said.
"The people of this region need a safe, resilient and reliable transport link between the east and the west of the central North Island," he said.
The first option is a new road across the Ruahine Range, north of the Saddle Road and the Te Apiti wind farm - this route is 15.7km long and would cost $350m to $450m and take up to six years to complete.
Option two is to upgrade the Saddle Road to a highway standard - this is 13.7km long and would cost $300m to $400m and also take up to six years to finish.
The final option is a new route south of the Manawatu Gorge - it is 19.2km long but offered the most direct connection to or from the southwest, costing $450m to $550m and take up to seven years to be constructed.
Five alternatives were ruled out by the agency for a variety of reasons including cost and ecological impact.
NZTA will gather more feedback on the shortlist until October 25 and announce a preferred route in December.