Why I should reconsider separated bike lanes...

efficiency.

See "What "bike friendly" looks like," by Alan Durning.

Separated bicycle lane, Copenhagen. (Photo courtesy of Jayson Antonoff, International Sustainable Solutions. See more photos here.)

From the blog entry:

These tracks, which are typically above street grade and below sidewalk grade, can move six times more people per meter of lane width than motorized lanes of Copenhagen traffic. That's right: because cyclists can travel close together, bike tracks have higher traffic "throughput" than do car lanes. Copenhagen has even synchronized its traffic signals -- for bikers. An average-speed bike commuter going downtown will rarely see a red light.