The occupants of two cars died after being struck by the fuel tanker trailer at Staghorn Flat on August 7, 2014.

The trailer decoupled from the truck and crashed into the two vehicles before coming to a stop on the western side of the Wodonga-Yackandandah Road.

Heavy Mechanics Pty Ltd has pleaded not guilty to one charge of failing to ensure people were not exposed to risks to their health and safety, relating to its servicing and maintenance of the trailer.

Terrence Bradbury had run BMR Truck and Trailer, which serviced the truck and trailer up until 2011, before Heavy Mechanics took over the contract.

Heavy Mechanics director Keith Haire said he would perform tug tests, which involved rocking the truck back and forth, to check if there was any movement between the equipment linking it to the trailer.

Mr Bradbury on Thursday told the Wodonga County Court he wouldn't use tug tests to check movement.

"You're really not going to have any idea if it's actually moving," he said.

IN OTHER NEWS:

"It would be very hard to see any movement."

Prosecutor Andrew Palmer, QC, previously told jurors it was "absolutely fundamental" the block connected to the trailer and tow eye be rigid, and "not any movement whatsoever".

The court heard Mr Bradbury's business had installed the tow eye coupling, which failed, more than three years before the crash.

A police officer estimated it had travelled about 356,000 kilometres in that period.

A mechanic who serviced the trailer with Mr Haire six days before the crash told the court he wasn't aware of any set mileage or timeframe the coupling could be used for before replacement, and said it was common to perform tug tests in places he worked.

He said he didn't feel any movement out of the ordinary during the last service, and said "it was all good".

The trial before Judge Christopher Ryan continues.