The closest I've come to a cycle track is a very lightly "protected" bike lane, with a couple of rows of cobblestone dividing it from the rest of the road. It's absolutely terrible, as it's way too narrow and full of potholes, being close to the edge of the road, but drivers still expect you to stay within that narrow little strip.
My gut feeling is that cyclists that will need to merge or interact with car traffic at some point should be visible to drivers, and not just pop up out of nowhere. Pedestrians do, but they're moving a lot slower and do not have the same need to keep up momentum that cyclists have.
Bi-directional ones sound like an accident waiting to happen.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett