From Slate's Nimble Cities project, we have an interesting piece stating the case for creating facilities for cyclists that are separate from vehicle traffic.
While the school of so-called "vehicular cycling" argues that cycles should be treated as cars and share the roads, this philosophy seems to be the result of (primarily American) cyclists adapting by necessity to their harsh surroundings rather than the sound basis of a widespread transportation shift. In the world's top cycling cities, one finds not muscular riders harried and buffeted by passing cars, but all manner of people—young, old, carrying groceries, carrying kids—riding on networks that have been designed for them.
One thing that seems clear, however, is that cyclist safety tends to improve as there are more cyclists. And the best way to get more cyclists is to make them feel safer. And the way to make them feel safer is, many planners argue, to provide separate facilities.
3 days ago