Some truck drivers are refusing to drive the "white knuckle" ride between Christchurch and Picton.
The coastal route on State Highway 1 is closed until at least Christmas because of landslides and cracks from the Kaikoura quake.
Now all drivers are forced to use the inland route while repairs are being made.
Some overnight truckies have quit their jobs, saying the volume of vehicles is too dangerous.
But the chairman of Marlborough Road Transport Peter Heagney says speeding and tight deadlines are the problem, not the traffic.
"I think it's fine. It's a road you have to treat with a bit of respect, that's all," Heagney says.
"In some cases, people are most probably on a tight time frame. One chap is saying that he's doing 400km on a night shift to Picton, then going back, 800 [in total]. He's most probably driving dangerously himself.
"The truck movement numbers are not that different to what they were."
The road could be open by Christmas but Heagney said he believed it could be open a lot sooner if more people were working on it.
He said there had been plenty of truck-driving jobs available because of people quitting but they had mostly been filled.
Picton driver Barry Peters left his employer last month because of fears about driving the route.
He told Fairfax he often saw truck-and-trailer units crashed along the highway.
"You go to work and you expect to get home again that night," he said. "I just wasn't enjoying going to work anymore driving that road."
- NewstalkZB