Very interesting blog post (also here) looking at a recent study into cities which implement bike share schemes (I think in the US):
All injuries fall by 28% in bike share cities versus a 6% rise in non bike share cities.
Head injuries fall by 14% in bike share cities versus a 4% fall in non bike share cities.
Serious head injuries fall by 26% in bike share cities versus a 6% rise in non bike share cities.
Pretty dramatic really. Bizarrely the study's main conclusion was that helmet use should be enforced in bike share schemes (even though serious head injuries already fell by 26% and we know that helmets aren't good for bike share).
Go figure.