I can't seem to find the link to the Copenhagen video that was floating around here a while back. But, if you have watched it, you will see that the average speed on the side-paths is pretty high - I would guess over 12 MPH and in the interview with one young man who was a physical therapist, he was doing at least 20 and passing lots of slower cyclists.

In my opinion, the Copenhagen side-paths are still to narrow.