One of the most respected 4x4 organizations has created an excellent guide to many of the trails in the Moab area. Rather than recreate their excellent work, we've opted to link to their guide.
We do re-classify the ratings to better suit our needs. We us a 1-4 rating. One being the equivelant of a dirt road that about any pickup could drive. 4 would require lockers front and rear and have risk of body damage and roll over. Beyond that would be buggy only trails.