The road between Whangārei and Auckland is about to be choked with trucks.

Waka Kotahi NZ Transport Agency and police have urged motorists travelling the route to be extra careful with a dozen trucks an hour set to leave Northport from 6am on Friday.

The trucks will be carrying about 1200 containers that couldn't be unloaded in Auckland from the ship Constantinos P.

The ship's diversion to Marsden Pt was seen as an opportunity for Northport to strut its ship-unloading stuff after adding a second crane early this year.

It docked on Sunday and it was expected trucks would begin moving the containers to Auckland tomorrow morning.

It comes as the Government's scrambling to ensure imports arrive in time for Christmas.

Transport Minister Michael Wood told Heather du Plessis-Allan says ships are being diverted to Tauranga and Whangarei.

"I've been talking with people like KiwiRail, so KiwiRail have put on 20 additional services between Auckland and Tauranga to get that freight moving."

An extra 800 freight trucks are rostered on to travel between Whangarei to Auckland for a week from Friday.

That start point has since shifted to Friday. Northport spokesman Peter Heath said the delay was because 1170 containers destined for Auckland had been stacked to be unloaded there.

The different configuration at Northport needed an extra 300 container movements to get the Auckland-bound containers off the ship.

"For us it's been a massive learning exercise and we said at the outset it would be. Hats off and huge thanks to everyone involved for being so supportive."

The containers will begin to leave Northport at a rate of 12 trucks an hour from Friday morning. The trucks will be making the journey to Auckland between 6am and midnight for seven days.

The traffic won't all be one way - empty trucks will be returning to Northport to pick up a new load.

Waka Kotahi vehicle compliance officers, Worksafe and the officers from the police commercial vehicle safety team would be on the route.

Senior Sergeant Mike Flatt said officers would be checking the number of hours truck drivers spent behind the wheel.

"We know that truck drivers can work long hours and we want to ensure all freight is transported in a safe manner. Our officers will be focusing on ensuring truck drivers travelling between Northland and Auckland are not fatigued and are complying with their driving hour limits, while also checking that the trucks are roadworthy."

Waka Kotahi NZ Transport Agency regional director Steve Mutton said motorists should plan more time for their journeys.

"We expect the roads to be busy in the lead-up to Christmas and there are only a few passing lane opportunities on the route. We ask motorists to be patient and give trucks space on the road for the safety of all road users.

"There may be delays on SH1 next week, and all drivers need to factor that into their plans. Trying to 'make up lost time' by speeding and unsafe overtaking puts everyone using the road at risk."

Mutton said roading workers would also be busy south of Whangarei to complete as much of the scheduled road resurfacing programme as possible before the holiday period.

with text from Newstalk ZB