Quad bike accidents common, farmers say

A farmers association says quad bike rollovers are common and people often don't understand the danger, after a seven-year-old boy died when the bike he was riding fell on top of him.

The boy was riding the quad bike with a nine-year-old pillion passenger on a Barellan property, 60km east of Griffith, on Sunday afternoon, when the pair tried to turn and fell off the bike, which fell onto the younger boy.

The National Farmers' Federation (NFF) said rollovers account for more than half of adult quad bike injuries and deaths.

"They're serious pieces of machinery, they are not toys," NFF workplace relations general manager Sarah McKinnon told AAP.

"This is the problem; people don't always understand the dangers that come with a piece of equipment like a quad bike."

The boy, who local media report had a twin sibling, was taken to Griffith Hospital and later airlifted to Canberra Hospital, but died overnight, police said on Monday.

The seven-year-old was understood to have been wearing a bicycle helmet when he crashed but Ms McKinnon said this would not have been sufficient.

"The bicycle helmet probably isn't going to be adequate, it should be a motorbike helmet or another helmet specifically designed," she said.

"Rollovers are common - it's 95-100kg that you have to lift off."

Ms McKinnon said it was hard to know how Sunday's accident might have been prevented.

"This is a devastating story. Having a passenger can affect stability but it's just hard to say," she said.

"Our hearts go out to the family. I think it's really important for everybody to understand the risks involved."

The nine-year-old boy was uninjured in the accident, which is under police investigation.