The upgrade is part of the Government's wider initiative for Christchurch designed to cut travel time for commuters.
The New Zealand Transport Agency Highways Manager Colin Knaggs said the project was making great progress and would probably finish ahead of schedule.
"We will have it substantially complete by this December. Despite a few road blocks people will notice the gateway arches taking shape in the next few months," Knaggs said.
The project will feature these 'Gateway Arches' at the interchange by the airport, which have a combined weight of approximately 400 tonnes. They were designed by arictectural group Warren and Mahoney and symbolise the crossing of paths, the Southern Alps and braided rivers of the Canterbury Plains.