It's wrong to compare cyclists with motorcyclists when considering compulsory helmet wearing.
- For motorcyclists, the speed of their own vehicle is a factor. You're saving quite a few motorcyclists from themselves, hence compulsory helmets and training.
- For cyclists, it's not the speed of the bike, it's the speed of the vehicle that hits them which is going to be the most significant factor. Cyclists still obviously make mistakes on their own, but at less bone/head-crunching speeds.
Stats:
Serious injury (no other vehicle involved)
- Cyclists 265, Motorcyclists 1146
Serious injury (1+ other vehicle involved)
- Cyclists 4041, Motorcyclists 4284
Ratio for cyclists: 265/4041 = 6.5% were serious solo accidents - surprisingly low
Ratio for motorcyclists: 1146/4284 = 27% were serious solo accidents - pretty high
Source:
Detailed statistics about reported personal injury road collisions for Great Britain, vehicles and casualties involved.
www.gov.uk
Look for RAS40004
Solution: fix the cause of the problem (other vehicles), not the effect (fragile cyclist's bodies).
Disclaimer: I'm a motorcyclist too.