"Westland will likely benefit more than the rest of the region and there may even be fewer travellers north of Hokitika," the report noted.
Haast Hollyford Ltd had indicated their existing cost benefit estimates needed updating and technical and environmental assessments were also required.
Detailed cost benefit estimates to cover "a broader range of factors" such as environmental costs, the displacement of visitors from other areas, economic flow-on benefits, and the impact on Milford Sound were not yet known.
Detailed environmental impact assessments and amendments to National Park management plans were among several issues that needed addressing.
Haast Hollyford Ltd had previously suggested the road be "called in" as a special project by the Minister for the Environment to facilitate the project.
However, given the scale of the project several central government agencies would need to be involved, along with the company and relevant councils, for it to be called in.
"This will ensure the case will be robust. It will also reveal sooner rather than later whether access to the conservation estate will be possible," the report said.
The case for both road projects "has not been proven", the report said.
"These two proposals rank relatively low on our criteria, largely due to the current limited evidence available.
"Although the potential benefits of these roads could be significant, the benefits will likely be captured mainly by the two districts the roads connect to and we consider that the direct and indirect costs are likely to be high."
Despite "this low rating" feasibility assessments and business cases were needed so the region and the projects' packers were "not left in doubt" either way.
- Greymouth Star