France, of course, is leading the way:
More than 10,000 unisex bicycles can now be rented for a nominal fee from 750 docking stations outside Metro stations and patisseries across the inner city.
By the end of the year, there will be 20,600 bikes at 1451 locations, meaning most people in central Paris will be no further than 300 metres from the nearest docking point.
The scheme is largely aimed at local commuters rather than the 16 million tourists who visit Paris each year, but any foreigner with a credit card will be able to borrow one of the sturdy three-speed bikes, which come with a large basket and lock.
The scheme — called "Velib", combining the French words for bicycle (vélo) and freedom (liberté) — is part of a longer-term push by the city to improve traffic flow, greenhouse emissions and people's health by promoting sustainable trans- port.