Public hearings on a proposal to build a new road and tunnel through the Mount Aspiring and Milford national parks begin on Monday.
Milford Dart Ltd is applying for a concession from the Department of Conservation to build about 12km of tunnel and road under the Humboldt and Ailsa ranges.
The tunnel would halve the nine hours it currently takes tour buses to drive from Queenstown to Milford Sound.
The Department of Conservation says it has received more than 1200 submissions on the proposal, with 400 in support and 859 opposed.
Public hearings on the application will be held in Te Anau on Monday and in Queenstown the following week.