In Finland some have used
seasonal:winter=no
to mark roads/tracks which have no snow removal and are marked with sign “Ei talvikunnossapitoa / Ej vinterunderhåll”

Example of bilingual sign:
http://farm1.static.flickr.com/241/456653860_fcf2c760b7.jpg?v=0

Another (better example) of such sign usage
http://www.flickr.com/photos/juandemiguelinkatu/4093095799/