Putting a third lane on the Waimakariri River bridge could cause more traffic congestion near suburbs in the Northern Corridor.
That's the fear of the Papanui-Innes Community Board, which will object to the plan this week, saying it will bring traffic problems to Belfast, Northcote, Casebrook, Papanui and St Albans.
The extra lane has been proposed as a way to deal with the congestion problems on the Northern Motorway for commuters from North Canterbury.
It is estimated to cost $20 million if done in conjunction with the Northern Corridor work - otherwise it would cost $34 million.
It would be used only by freight, trucks and buses and would include a separate cycleway to improve public transport reliability and provide a safer cycling option.