View: http://www.youtube.com/watch?v=5q9jPQHqPCA
I see a cyclist do this at least 3 times a week, they see a picture of a bike and jump in the lane, even though they're going down it the wrong way! I know it's genuine confusion and no real harm's done, but it can be a pain when a large vehicle is using the main lane at the same time.
) which are two-way but only have a single painted bike indicating that they exist - just like that contraflow.