FARMERS face the prospect of a crackdown on the safety of fruit-bin trailers after a Swan Hill grower appeared in court over a fatal car crash.

Swan Hill Magistrates' Court heard this month that the empty fruit-bin trailer Richard Dow was towing came unhitched and smashed into another car, killing the female driver.

Mr Dow, 38, was convicted and fined $700 when he pleaded guilty to a charge of failing to securely couple the trailer to his Holden utility on December 18 last year.

Afterwards, investigating officer Sergeant Les McPhee said a report would be prepared for the Victorian Coroner.

In it, he said he would recommend the laws be changed to require that fruit-bin trailers be equipped with safety chains in the same way as registered trailers, which must also have lights and - depending on size - brakes.

The court heard Mr Dow was towing the empty 6m by 2m trailer at about 50km/h along Woorinen Rd to his farm, when the circular spring clip securing a drop pin in the single-tongue tow hitch snapped and the trailer came adrift, tearing the side off a sedan travelling in the opposite direction.

Mr Dow had taken the trailer to have straps fitted to stop the fruit bins from falling off and was towing it back to his farm for use during harvest.

The trailer coupling, made by a local engineer, was two weeks old and the spring clip was two days old.

Police said they found a double-tongue tow hitch in the back of Mr Dow's ute, which would have reduced the up and down movement of the trailer drawbar, and "had it been used, it would have reduced the likelihood of the trailer detaching from the towing vehicle".

Police prosecutor Senior-Constable Stuart Tompsett said fruit-bin trailers were "exempt from registration and the standards of registration requirements".

In Mr Dow's defence, barrister Tony Phillips said the trailer was no different to those used by many fruit growers.

"It's industry standard - there are hundreds of these trailers," he said.

"This is not a farmer taking a shortcut, this is a farmer using an engineer to construct something that will do the job.

"The frightening thing was the engineer ... has indicated this sort of thing can happen with any coupling, if it breaks."

Magistrate William Gibb said there had been a breach of the law, so there must be design standards that should be met.

"That follows as a matter of logic and common sense," he said.

"And when one is trying to design a trailer or a coupling, surely you'd make contact with the authorities on this and ask if it meets the standard, and then they would have been told no it doesn't.

"I can see some recommendations coming out of the inquest on this."

A VicRoads spokeswoman said fruit bin trailers were exempt from registration and did not have to comply with the same standards as a registered trailer, under regulation 258 of the Road Safety (Vehicles) Regulations 2009.

"We know that they do short journeys on local roads and we haven't seen numerous issues with these vehicles," she said.

"For the most part, if they're doing short journeys, mostly on-property and only darting on and off local roads, there's no real problem."