London's Not-So-Super Cycle Highways

"Unfortunately, not all junctions can be passed underneath, increasing journey times by leaving cyclists to cross at pedestrian crossings.

And at points, the bright blue lanes stop completely, meaning pedestrians and cyclists have to share the same space for portions of the route, with little visual clues for cyclists as to which direction the route is following."

The system is broad, but some slight breaks in its continuity create confusion along the way, according to this highly illustrated post.