Australia averages 13 quad bike deaths per year (cf 1200 road deaths) - so more than 1%, and my daughter lost a friend that way at High School. They are often used by kids on private land (one in six fatalities), and the "questionable" places tend to be slopes that kids misjudge on the family farm. It does not seem a major inconvenience if it is standard.
“Quad bikes are the leading cause of fatalities in Australia of all consumer products that aren’t regulated,” the assistant treasurer says.
" Across Victoria, a child goes to hospital every five days because of quad-bike trauma, he says. ....60 per cent of quad-bike fatalities were caused by rollovers.....about half those killed in quad-bike incidents would have survived if they hadn’t been crushed or pinned by the bike.....We know that around 60 per cent of quad-bike fatalities are caused by rollovers, and the operator dies from asphyxia in around half of these.”