Graham Brown keeps a small log about the size of a weekend newspaper near his quad bike to remind him how it nearly took his life during routine spraying on a gentle slope at an equally gentle speed.
When the vehicle's wheel caught on the log, the 250-kilogram quad rolled over the Orange farmer. Mr Brown's ribs were broken and shoulder injured, and he needed a hip replacement. The accident reduced his ability to work by 70 per cent for three years.
“Had I been pinned under it, I may well have suffocated,'” Mr Brown said.
Quads are advertised as all-terrain vehicles, but even a “tuft of grass” is enough to destabilise one, according to research published in Safety Science.
The research adds to the growing evidence that has found quad bikes – a $230 million market – are unsafe without rollover protection.
Since 2001, there are have been more than 200 quad-bike related deaths in Australia, and about 8000 people have been hospitalised with serious injuries caused by quads.
About 64 per cent of the deaths occurred on farms, which makes quad bikes the biggest killer of workers in Australia.
The latest research found quads were "particularly vulnerable to a rollover, even when travelling around farming environments where they traverse relatively small bumps on typical grassy slopes at moderate speeds".
"Such small bumps are not readily perceivable as a hazard. Moreover expecting a surface on a grassy hill to be smooth is not realistic within a farming environment," said the paper by David Hicks and Professor Raphael Grzebieta of the University of NSW's Transport and Road Safety Research.
As the angle of the slope increased, the size of the bump needed to roll the vehicle became smaller.
An earlier report found almost one-third of quad bike fatalities occurred on terrain with an incline, and almost half occurred on uneven ground with fallen logs.
Mr Brown used to train workers before he let them ride a quad, and even then there were a few minor incidents. Now he won't let anyone else other than him on the quad, saying he knows his land and his machine best - and he drives cautiously and wears a helmet.
"I still see quads as a useful tool. It's about them being fit for purpose," said Mr Brown, but he recommends others should purchase a side-by-side vehicle instead if they can afford the more expensive vehicle, which has seat belts and rollover protection.
The Federal Chamber of Automotive Industries, which represents quad bike manufacturers, recommends "active riding" where a rider stands or leans to shift the centre of gravity on a slope or bumps.