Side comment about County Roads
I know you're asking about a trail OFF to the SIDE of a seasonal road, but . . .
I have a 38 page dissertation written by the Muskegon County Road Commision's staff of attorneys. It gives a bit of history of the McNitt Act and then delves into the court cases that have shaped what is and isn't a road and what the rules are for their use, incorporation into the system, and abandonment.
Keep in mind that a county atlas (even the Michigan Gazetteer) is NOT necessarilly accurate!!!!!!!!
The only way to be sure it is STILL a legal road is to ask the CRC if a road in question appears on the Counties CERTIFICATION maps. These are the maps that tell the State which roads the county claims for the purposes of road funding.
If anyone wants a copy of the dissertation, let me know.