The revelation came at an inquest into the death of Nathan Zanuso, 27, who died after a head-on collision with a B-double at Ulmarra on the NSW north coast in February 2010.

It emerged the driver of the truck, Robert Pearce, 52, had fallen asleep at the wheel and veered onto the wrong side of the road, causing the collision.

Pearce was convicted of negligent driving occasioning death but given a suspended sentence after an independent medical specialist found that he suffered from sleep apnoea, which repeatedly disturbs a person's sleep and can lead to extreme drowsiness.

On Wednesday NSW Coroner Mary Jerram heard from two leading sleep illness experts, both of whom had undertaken research which shows that 50 per cent of long-haul truck drivers suffered from the condition.

''As a group, they tend to exhibit many of the risk factors associated with sleep apnoea, in that they are middle-aged males who are often overweight and obese,'' said Sydney University Professor Robert Grunstein. His study of 1000 truck drivers last year found 46 per cent suffered moderate to severe sleep apnoea, double that of the broader community.

A fellow sleep illness expert, Dr Anup Desai, said in his experience there were serious problems with the medical checks given to truck drivers.

''There's a huge gap [in the assessment process] where there are people assessing these drivers … are aware of sleep apnoea, but it doesn't seem to be transferring into actual sleep assessments,'' Dr Desai said.

He said this was partly a problem with the assessors but also the reluctance of truck drivers to be assessed in fear that they will be taken off the road.

''There's a culture of fear to some extent that leads to a reluctance in going for assessment. It isn't warranted because most physicians try to keep people on the road as long as they're being treated. ''That research was funded by the RTA 10 years ago but we're still having these conversations about truck drivers.''

While there was a very high prevalence of sleep apnoea among drivers, it did not mean that they were all unsafe.

''There's evidence that they can still be good drivers - the important thing is to make an assessment about whether they are at risk of falling asleep while driving,'' Dr Desai said.

The counsel for Roads and Maritime Services, Michael Spartalis, said the department had ''not been sitting on its hands'' but was addressing the issue of driver fatigue.

Ms Jerram recommended that the NSW Transport Minister provide extra funding for professional research into the fitness and health of long haul drivers. The truck driver Robert Pearce said outside the court that he supported the recommendations, and had better checks for drivers been in place years ago his accident may have been prevented.