Mr I'Anson told 300 people at the meeting he wanted a three- to four-year time frame for the road.
But the four preferred options - an upgrade to the existing Saddle Rd, a new road north of the Saddle Rd, a new road south of the Saddle Rd and a new road south of the Manawatu Gorge - come with either a five- to six-year, or six- to seven-year, timeframe.
State Highway 3 through the Manawatu Gorge has been closed since large slips caused major damage to the road on April 24 after severe weather.
Geotechnical investigations and long-term monitoring have established the hillsides in parts of the gorge are highly unstable and the gorge road is no longer viable as a safe long-term transport route for the region.
The NZTA has been working with the community and other key stakeholders in recent weeks to evaluate an initial long-list of 13 alternative options.
"We've been gathering valuable feedback on the initial long-list, and we're pleased to be taking the next step, with the release of a shortlist of four options that will be further investigated," Mr 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.
"It's essential for the economic wellbeing of New Zealand and our communities and with the gorge route no longer a safe option we're working with urgency to make it happen."
But Mrs Collis said five to six years is too long.
"There will be businesses, especially in Woodville, who will be looking at their options," she said. "We know there is 30 per cent of traffic no longer going through Woodville and a marked decrease in vehicles travelling through the Tararua. And there's's a concern about the cost of freight in our region."
Chris Chapman, network manager of the Tararua Alliance, said his preferred option is number three, a new roading corridor across the Ruahine Range, south of the Saddle Rd.
And he and his roading team have always expected a five- to six-year timeframe.
"At the meeting in Woodville when Ross I'Anson said three to four years, we raised our eyebrows," he said. "With a geological survey, land purchase, iwi consultation and consenting before even a spade is put into the ground, five or six years seems logical.
"But if we have another two years of the wet weather we've experienced, that timeframe would blow out."
Allan Benbow, the Tararua District deputy mayor, a member of the group preparing the business case study for the alternate route, has said the process has been robust.
The NZTA will be gathering public feedback on the shortlist until October 25, with a preferred approach announced in December.
Mr I'Anson said the agency is encouraging people to provide their ideas and perspectives on the shortlisted options.
"We know how important this connection is to local communities, and a very important part of the process is working with our communities to make sure we get the best possible transport solution for the region and the whole of New Zealand."
And while the timeframe will be a blow for some businesses, there will be opportunities, Mrs Collis said.
"Accommodation and food businesses in Woodville will benefit during construction and businesses will need to think positively."
The shortlisted options for the alternative to the Manawatu Gorge. Information on costs, length and construction times are approximate.
Option 1: North of Saddle Rd:
This option would provide a new road corridor across the Ruahine Range north of Saddle Rd and the Te Apiti wind farm.
•Cost: $350m-$450m
•Length: 15.7km
•Time to complete: 5-6 years.
Option 2: Saddle Rd upgrade:
This option involves a major upgrade of the existing Saddle Rd corridor to bring the route up to state highway standard.
•Cost: $300m-$400m
•Length: 13.8km
•Time to complete: 5-6 years.
Option 3: South of Saddle Rd:
This option would provide a new road corridor across the Ruahine Range south of Saddle Rd.
•Cost: $350m-$450m
•Length: 12.4km
•Time to complete: 5-6 years.
Option 4: South of the gorge:
This option is for a new route south of the Manawatu Gorge providing a new road corridor which offers the most direct connection for travel to or from the southwest.
•Cost: $450m-$550m
•Length: 19.2km
•Time to complete: 6-7 years.
