Bike sharing is bursting out all over, and Paris' Vélib system was the urban bike sharing breakthrough that really started this fast-spreading trend. In México City there's now Ecobici (1,100 bikes); in Teheran there's Bike House (around 425 bikes), in India there's FreMo (100 bikes), and in Denver the much-hyped B-cycle will kick off on Earth Day. And what does the father of bike sharing, Luud Schimmelpinnink - he conceived the White Bicycle system back in 1965 - think of all this? While happy that elements of his vision for bike-based inner-city travel is coming true globally, Schimmelpennink is eager for the fourth generation of urban bike sharing to appear, and (surprise!) he's got a design for a system that integrates the features that many believe will grace bike sharing and urban biking's future. Schimmelpennink's design for a sturdy bike for Amsterdam and other bike-friendly cities is based on a pedal-assist electric bike with a chainless shaft drive and a hub motor in the back wheel.The rest of the bike's electronics are neatly hidden in the frame tubing. Schimmelpennink said electric assist is necessary in the next generation of bikes for a couple of reasons. The first is to appeal to a wider field of riders - while Amsterdam is generally flat and has a fairly small inner city loaded with bike lanes, in other cities hills are a minor to intermediate challenge for riders.In addition, however, the electric component of the bike is important for system maintenance and control. When the bike leaves a designated city area, the system can via GPS find the bike and reduce power to to the pedals, making it difficult to ride. Read more in Tree Hugger.