More logging trucks will be unleashed on to State Highway 1 between Auckland and the Far North from today because of a suspension of all Northland's freight trains.
Trucks carrying milk powder to Auckland and Tauranga from Fonterra's big dairy factory at Kauri, north of Whangarei, will also hit the road as KiwiRail reconfigures its fleet to cope without 40 Chinese-made locomotives contaminated by asbestos.
Campaigners for keeping rail in Northland - who are supported by a petition of 13,471 people - fear the region's roads will have to carry about 200 more trucks a day because of what one said yesterday was an ill-conceived purchasing decision by the Government operator.
Jon Reeves of the Campaign for Better Transport included the suspension of rail services on the Dargaville branch line, and from Otiria in the Bay of Islands, in estimating the number of extra truck trips needed instead.
Save Our Rail Northland organiser Alan Preston has written to KiwiRail seeking information justifying its decision to suspend all Northland services simultaneously.
Automobile Association Northland chairman Stephen Jarman is relieved by an assurance by the company that the suspension is temporary, but says motorists should be extra cautious when coming across even more trucks than usual.
The region suffered 21 crashes involving logging trucks in 2012.
Whangarei Mayor Sheryl Mai said Northland needed both better roads and the maintenance of rail to thrive, but she did not believe the long-term survival of the North Auckland Line was in doubt.
"It's vital, it's absolutely critical to our future," she told the Herald.
Although word of the suspension was a surprise to her, she said she would ask police whether anything could be done to improve road safety in the meantime.
Mr Reeves does not share her optimism about the future of Northland's trains, fearing the suspension may prove a nail in their coffin.
KiwiRail has been considering their future since 2010 under its $4.6 billion turnaround plan, which gives priority to main trunk freight services between Auckland and Christchurch.
Spokeswoman Jenni Austin said the company was still looking at ways to attract more business to the northern line, and no decision about its future was imminent.
She said KiwiRail would take advantage of the suspension to perform track maintenance work.
But Mr Reeves said that if the company was serious about building up business, the last thing it would do would be to suspend services and refer customers to road carriers.
"I think it's 101 in business - you don't close your doors when you're trying to build up the service."
Ms Austin said KiwiRail was having to reconfigure services throughout the country, as the 40 suspended Chinese locomotives were the most powerful of its 177-strong fleet.
"They represent quite a significant chunk of our pulling power," she said.
She could not predict the duration of the suspension, except to say: "We are hopeful it won't be too long."
"Clearly we need to know these locos are safe before they are back in operation. That's our first priority, the welfare of our staff."
KiwiRail said in a statement on Friday that testing had been completed on the locomotives, showing no airborne asbestos fibres, "and we are now able to begin working towards a phased reintroduction."
"However, it will be at least another week before this begins to happen, so there will continue to be some impact on rail freight capacity for our customers."