Bicycling advocates envision a future in which bikes are a widespread daily form of transportation. While many global cities are seeing the number of bike commuters increase, this future is still far away; at times, urban cycling seems to be fighting for its very survival. Will we ever witness a true "bike boom" in cities? What can we learn from past successes and failures to make cycling safer, easier, and more accessible? Use of bicycles in America and Britain fell off a cliff in the 1950s and 1960s thanks to the rapid rise in car ownership. Urban planners and politicians predicted that...