OpenStreetMap
There's no widespread use yet. Wiki has no clear suggestion. I distilled
highway=path
snowshoe=yes
_or_
highway=path
snowshoe=designated
access=no
{for exclusivity osm.wiki/Tag:access%3Ddesignated}
and optional:
relation=route
route=snowshoe
name=....
Discussion
Comment from Kevin Steinhardt on 26 December 2009 at 15:23
Just one question: what's a snowshoe? :P
Comment from bass on 26 December 2009 at 21:21
http://www.usscouts.org/clipart/library/WOSM/Canada/General/snowshoe.gif
Comment from Skippern on 26 December 2009 at 22:06
snowshoe=designated (when wearing snowshoes you are obligatory to use this route even if alternatives exists)
snowshoes=yes (you are allowed to use this with snowshoes)
snowshoes=no (you are not allowed to use this with snowshoes)
The only sane usage I can see with this is together with ski-tracks, where I would understand usage of snowshoes might damage the prepared tracks, and therefor prohibited or regulated in some way. If it is a regular "snowshoe walking route" or "snowshoing event" than relation=route should be used.
Comment from Iridium on 4 January 2010 at 07:51
Of course, I thought of routes that only exist when there is snow that are only doable with snowshoes. Well you could do on foot, but would sink like knee deep into snow... otherwise a simple "snowshoe=yes" on whatever would be enough.