"It was quite horrific," an emotional Mr Campbell said.
"The fatigue’s horrible."
He recorded 33 instances in just over four months earlier this year where he said he worked beyond the legal 13 hours per day.
Southfuels has since become part of a new entity, Fern, as part of a joint venture with Farmlands.
Legally, truck drivers are only allowed to work 13 hours per day, or 70 hours a week.
But former staff spoken to by the Otago Daily Times said it was common to work over that.
Mr Campbell said he had debated whether to speak out about his experience, but felt if he did not, someone could die.
"It makes me really angry. I almost gave up driving over it."
He has contacted both Waka Kotahi NZ Transport Agency and WorkSafe, which were both looking into the allegations.
An experienced driver based in Christchurch, Mr Campbell drove for the company around the South Island including in Otago and Southland.
The ODT has seen three emails sent by Mr Campbell to one of his managers, where he raises concerns about fatigue and working over his hours.
In the first, he asked the manager to look over his workload for the previous fortnight, saying he was being pushed to the limit and still not getting all his work done.
"Apart from the issue around fatigue management I’m not sure I can maintain this pace indefinitely. Also there is an elevated risk of a mishap being constantly under the gun like this," he wrote.
Four days later he emailed the same manager saying he was struggling badly with fatigue "to the point I’m starting to make stupid mistakes".
Ten days after that, he said he had been outside his hours again the day before and the hours were not sustainable or safe.
During one shift he said he fell asleep three times during a 200m stretch of road.
To get around the electronic logbook system, drivers would add their additional hours to days where they had not actually worked, he said.
He suffered anxiety attacks and nightmares, and alleged he was bullied in an effort to get him to leave — he did soon after.
The ODT has spoken to other former employees who were also aware of staff working over their hours.
One, a former manager with the company, said it was pretty common for staff to be expected to drive back to Dunedin from places like Invercargill after finishing their work, adding hours on top of their legal limit.
"It used to be a good company to work for, and now it wasn’t," he said.
Fern Energy chief executive Bryan Jamison said the company was "aware of negative commentary about our operations that a former employee of Southfuels is currently circulating".
"Fern takes our Land Transport and Health and Safety obligations extremely seriously and we do not take shortcuts when it comes to the wellbeing and safety of our staff."
The former employee worked with Southfuels for a very short period and chose to resign from the business when conduct and performance issues were raised, he said.
"As this is an ongoing employment relations matter and for privacy reasons, we will not be commenting further."
A WorkSafe spokesman said it was conducting initial inquiries to determine the appropriate response.
Waka Kotahi declined to comment on any potential inquiries that were ongoing, but it is understood to be investigating.
As of mid-December, that investigation remained ongoing.
"[We take] logbook compliance extremely seriously given the potential for fatigue to lead to serious and more than likely fatality crashes where large freight trucks are involved — for drivers as well as other road users," South Island compliance manager Kelvin Lloyd said.
"To some, fatigue might seem like a minor concern, yet it costs companies millions of dollars each year in excess costs, accidents and errors as well as costs to society as a whole."
The social cost for fatigue-related crashes in 2019 was $283 million, he said.
First Union transport, logistics and manufacturing organiser Justin Wallace said being asked to work extra hours was part of the normal life of a truck driver.
The union had concerns about how many hours drivers were being asked to do, he said.
"Even though in some cases drivers are paid well for their jobs a large majority work longer hours to financially survive.
"This is particularly the case in the last couple of years as the cost of living rises so does the need to work longer hours to compensate."
