The Transport Agency's appeal against a decision to block the construction of a flyover around the Wellington's Basin Reserve will be heard in the High Court in Wellington from 20 July.
A Board of Inquiry halted plans for the $90 million project last year, which was promoted by the agency as a way of reducing traffic congestion.
The board's decision will be defended by lawyers hired by citizen groups, including the Save the Basin Campaign.
Spokesperson for the campaign Tim Jones said the groups were now trying to raise $50,000 to pay for their legal representation.
"Our aim is to raise $50,000 for our representation at the High Court appeal. We're the first group challenging a project in the board of enquiry process to win, we think that puts us on the front foot."
Mr Jones said the appeal was scheduled to last two weeks.
The flyover was opposed by several lobby groups representing residents and those concerned about the loss of heritage features in the capital.