We've ran into people walking on sled trails in NH, they would hold their noses when we rode by because of the 2stroke smoke. Me being me I just had to stop and ask directions while the sled idled and got an earful about being on the trail, it was a groomed sled trail and I guess they figured it was groomed for them to walk on.
Have ridden by NH f&g while they were ducked behind their sleds taking radar, thought that was the most pathetic thing I ever saw.