I would think virtually all motorcycle accidents are avoidable and as such are caused by the rider.
Not sure I agree.
From 2012 Motorcycle Accident Statistics for Great Britain (but I'm darned if I can find the original source on the UK Gov web site):
'The most common reason for accidents caused by car drivers was by failing to look properly (24%), whereas apart from bus and coach drivers, motorcyclists were the road users least likely to cause an accident for the same reason (16%).' Source:
http://www.motorcyclenews.com/news/2015/march/new-accident-stats-show-large-decrease/24% sound like they might not have been avoidable by any motorcyclist involved, at the very least.
Many more bikes leave the road on bends than do cars.
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/568484/rrcgb-2015.pdfpage 112
(I had to calculate the percentages myself)
Going ahead on a left-hand bend:
% of motorbike accidents = 4.9%
% of car accidents = 3.2%
Going ahead on a right-hand bend:
% of motorbike accidents = 4.8%
% of car accidents = 3.7%
The rate of bike crashes on bends is definitely higher than for cars, but maybe not at the level of 'many'.
Definitely below 'twice as many' for example. I was expecting it to be higher too.