At least 12 truck drivers have quit because they are concerned about the safety of a new alternative highway between Picton and Christchurch, their union says.

Photo: RNZ / Claire Eastham-Farrelly

The inland route via the Lewis Pass was never intended to be a main arterial route but that changed when the Kaikōura earthquake forced coastal sections of State Highway 1 to be closed.

Five people have died in crashes on the alternative route since the quake in November, with the latest smash occurring yesterday when two people died after a car and a truck collided just north of Culverden.

Before SH1 became impassable, the Picton to Christchurch route took drivers about 4.5 hours, giving them enough time to make the return journey on the same day.

The windy narrow inland route had nearly doubled their drive time, but First Union organiser Bryce Hamilton said freight companies and their customers were still insisting the trip was done in one day.

This pressure, combined with driving a road that was never meant to be the main highway, was the reason so many were now either quitting the industry altogether or finding work on less dangerous routes, he said.

Photo: Google Earth

"They know that on a long enough timeline their survival rate will drop to zero if they keep driving that road because they've been in the game for, some of them, upwards of 30 years and they know that it's dangerous in their heart of hearts.

"They say to their employer, look, you know, thanks for the employment but I don't want to do this, it's just too unsafe."

There was not enough incentive for those employing drivers to make their jobs safer, he said.

"We want to see better regulation, we want to see WorkSafe investigating road incidents with trucks. We want to stop the blaming of drivers because they're very professional at their job. We actually want some of these operators to be held to account because we're putting people out on the road there that have accidents and they do kill."

The Road Transport Association's Marlborough chairman and a trucking company owner, Peter Heagney, agreed some owner-operator drivers were pushing the limits and making the route unsafe.

"People [are] doing unrealistic schedules on their trucks to try to get the work done in that period. Some of the ones that are working for some people, they've got them screwed down to such a ridiculous rate, people are most probably pushing the envelope a bit harder to try and make a dollar," Mr Heagney said.

Photo: RNZ / Rebekah Parsons-King

And because the route now took almost twice as long to cover, more drivers had to be hired - which meant there were more inexperienced drivers on the road.

"The last thing we want is an accident and we don't want other people having accidents."

Marlborough's head of road policing, Sergeant Barrie Greenall, said the end of the busy summer period and a fall in numbers using the roads had bred complacency amongst some drivers.

"What we've seen recently is, as the traffic volumes start to drop off, the opportunities for those that want to make poor choices and try and cut down the time has increased and we're starting to see a rise in incidents and accidents," Mr Greenall said.

NZ Transport Agency earthquake recovery manager Steve Mutton said $60 million had been spent upgrading the road and the agency was about to begin consultation on bringing in permanent speed restrictions on parts of the alternative highway.