A hefty $40,000 dollar fine handed down to farmers for refusing to wear helmets on their quad bikes is considered a clear signal.

The Marlborough couple had been warned by Worksafe New Zealand after being seen without helmets several times.

Worksafe New Zealand manager of National Programmes Francois Barton says the fine is a reflection of the judge's view of the breaches.

"I think what it signals is quad safety is a critical priority and I guess everyone on farms need to take ownership of that responsibility."

He agrees it is a significant fine.

"There was no need for us to get to this point. What you had is five conscious decisions over not a short period of time, where this couple said they didn't want to comply."

Mr Barton says Worksafe is seeing a number of farmers changing their habits, and wearing a helmet.

And a report shows helmets aren't being used enough by children on quad bikes.

The report - written for the Health Quality and Safety Commission, shows quad bikes, motorcycles and other 'off-road vehicles' accidents are the country's second largest cause of recreational deaths in children under 15.

Chair of the committee behind the report, Dr Felicity Dumble says helmets aren't being used as they should be.

"It's been reported that a quarter of quad bike injuries involve injuries to the head and a quarter of child quad bike hospitalisations involve head injuries."