In comparison to automobiles, bicycles are a paragon of energy efficient personal transportation with the bicycle roughly 50 times more energy efficient than driving.[61] Bicycles increase mobility while alleviating congestion, lowering air and noise pollution, and increasing physical exercise. Most importantly, they do not emit climate-disturbing carbon dioxide.[2] Bike-sharing programs are beginning to boom throughout the world and are modeled in leading cities such as Paris, Amsterdam and London.[62] Bike-sharing programs offer kiosks and docking stations that supply hundreds to thousands of bikes for rental throughout a city through small deposits or affordable memberships.[63]