If I remember rightly, Amsterdam filled up with so many bikes, it got to the point there was always one available at arms length. No one bothered owning one anymore with the "two for everyone" effect ! Unfortunately it got to the stage where getting around was so impeaded, the canals started to fill up with bikes chucked out the way. What it cost then to clear up the waterways, or where they went from there I don't know, but I think dredging the Thames might be more expensive. But maybe if they are alowed to get impacted enough it would be a good enough a foundation to tar-mac over it and have a new express way.