Pete Owens wrote:And 2m is not wide enough for a 2-way route shared with pedestrians.
The Trent and Mersey canal near me is part of NCN route 6 (Swarkestone near Derby) there is no tarmac and the gravel bit is barely 12" wide yet this is a 2-way cycle route with lots of pedestrians in summer). There is plenty of room there to widen the path to 2m which I think would be more than enough. Anything more than a couple of metres would invite misuse and spoil the tranquility of the canal.