That fact that it is groomed, has only sled tracks and no big ruts from quads running up and down it should be far more obvious than the signage on the trees or posts. You do not mistake a sled trail for a quad trail. And within 50 ft when you sink up to the axles and leave big ruts you realize you are destroying a perfect sled trail. There is only one explanation for anyone continuing beyond that point - they simply don't care who will use the trail after them.
If it was paved, had a posted speed limit, and had lines painted in yellow and white, you would assume its a __parking lot leading to a trail system__. Not hard to fill in the blank, unless you are saying that quadders can't figure it out.
Your assuming people know or should know the difference, they just see a trail system. I didn't until i started browsing forums regularly looking for people and places to ride. How are people supposed to know if they haven't been told?
I guess what bothers me most is the OP post about slashing the offenders tires and breaking his orbital bone. Ya it was a rant but it made wanna post my thoughts.
Its about education and etiquette. And now i have bad trail cred
My 2cents im out