Christchurch's heavily-congested northern corridor is facing increased pressure as North Canterbury's population swells at a rate three times faster than forecast.
It is bleak news for traffic-weary commuters already facing lengthy waits at peak times.
The Canterbury Transport Operation Centre (CTOC) has recorded buses taking 22 minutes to get from the old Waimakariri Bridge to the Chaneys off-ramp.
Waimakariri district's building consents have leapt from 488 in 2011 to 1278 in 2013, meaning old projections of six years growth in two years have been superseded.
Chief executive Jim Palmer said trends for the first two months of 2014 now indicated there would be nine historic years growth in three.
"On top of this, we went from a functional rental marketing and accommodation to a very full rental market. All of those things combine to a level of uptake and growth in our district we haven't seen before," he said.
Congestion on the motorway was also starting to "translate into issues" for greater Christchurch, Palmer said.
The district council, NZ Transport Agency (NZTA) and CTOC are scrambling to find interim solutions until the multimillion-dollar motorway project planned for 2017-2020 can be built.
NZTA is building a four-lane highway between QEII Dr and the existing Northern Motorway.
A western corridor including a four-lane highway from The Groynes to the centre of Hornby and a bypass of Belfast is also planned but both are still at the consent stage.
NZTA southern director Jim Harland is leading a team of experts tasked by the district council to find short and medium-term solutions. He is expected to report back to the council in two months.
Driving patterns were "varied and unstable", Harland said.
"Journeys can take 40 to 50 minutes one day and then the same journey on a different day, same time, can be more than an hour."
Rangiora commuter Rachel McClung said she had tried leaving at different times to get to her Addington workplace but it made no difference. "Rush hour is now basically between 6.15am and 9.30am," she said.
Harland's team will use information gathered from bluetooth technology to analyse where people are going from the northern corridor.
The technology picks up a mobile device in a car and tracks where it goes.
"This gives us a real-time information - how long different trips take and where people are going," he said.
Leese Rogers, an IT consultant who travels from Leithfield to Riccarton for work, has resorted to working from home on bad traffic days.
"The traffic has got progressively worse each year since I moved out to Leithfield about four years ago. The motorway is a joke and it's generally backed up and takes half an hour just to get down it."
University of Canterbury transportation engineering senior lecturer Dr Glen Koorey said it was a short-term option motorists might need to consider.
A behavioural change in people living near where they worked was needed to help reduce congestion, he said.
"The solution is always to build a new motorway but it is a never-ending cycle."
Environment Canterbury did not respond to emails for comment on future bus use and priority lanes.
- The Press