The utopian idea of bicycle highways is becoming a reality. Copenhagen has one in the works, and a series of bicycle interstates has been proposed for the U.S. as well.
"The bicycle highway - no red lights, no cars - is every cyclist's fantasy. There are now signs that infrastructure is catching up with the dream. In October 2008, an association of U.S. state-highway officials approved the concept of a national Bicycle Routes Corridor Plan - the first step in potential American bike Interstates. But this amounts to little more than a go-ahead for states to put bike-route signs on existing roads.
Copenhagen, however, began last month to create the real thing: a system of as many as 15 extra-wide, segregated bike routes connecting the suburbs to the center of the city."
Other ideas include plans to build plant-like structures that absorb CO2, and the addition of noise to quiet hybrid cars.