The finding of a Bathurst Coroner's Court on Wednesday pointed to only two brakes on the 1978 Kenworth semi-trailer operating efficiently on June 22, 2005 when Paul Manwaring, 29, was fatally injured.

Mr Manwaring was thrown from the truck, owned by Rod Pilon Transport, and died 10 days later from brain injuries, Coroner Thomas Hodgson said.

Mr Manwaring had suffered the injuries when his truck laden with bales of cotton left the Mid Western Highway about 12.30am and crashed from a rest area into a tree.

Mr Hodgson commented on the submissions of police prosecutor, Sergeant Brett Donaghy who said the fact brakes on the truck had been faulty was of great concern, as was the level of maintenance work carried out on the truck.

Sergeant Donaghy made reference to Mr Manwaring's driving, as described by two witnesses in a car following the truck, saying he was possibly trying to control the truck to avoid a serious accident.

The court has now referred inquiry transcripts to WorkCover.

The coroner remarked on an RTA report that found evidence of worn brakes and chassis cracks on the Kenworth truck.

Mr Hodgson said speed was not a factor, self harm was ruled out, alcohol not a factor, a small amount of cannabis had been found in Mr Manwaring's blood.

Mr Hodgson said motor vehicle defects had been the most likely cause of the accident, that the driver's side door would not open, a front axle assembly had recently been replaced, and brake efficiency had been reduced.

Mr Hodgson had regard to evidence given by Rod Pilon, the owner of Rod Pilon Transport who said he'd not been made aware of faults with the truck. Mr Pilon said there should have been a service history of the truck available.

Mr Hodgson said Mr Pilon had been cross examined and appeared very defensive, not sure, did not know and had not been a reliable witness.

Mr Manwaring had started working for Rod Pilon Transport on December 6, 2004.