Way too many factors to say how truly dangerous riding a motorcycle is.
You have to take into account:
- use of alcohol/drugs. Riding requires hand/eye coordination and quick reflexes. Both things alcohol diminishes
- use of riding gear/safety equipment. A guy on a Harley wearing a plastic helmet that looks cool, vs a rider in full riding gear.
- level of riding ability.
-type of riding. Very aggressive fast riding seems a whole lot more dangerous than cruising and riding defensively