Been working on a Garmin trail map of the Great Lakes area the last few years and have uploaded it to GPSFile for free. The map contains Michigan DNR Jeep Routes, Drummond Island and Appleton OHV trails, National Forest roads, and a few state roads and seasonal roads (MI) in the Great Lake states (MI, MN, WI, IL, IN & OH). MI DNR routes are one color, US forest roads another and so are state trails. Drummond Island trails are color coded by difficulty like the paper map. Dead end trails are color coded the same except they are broken lines. Many non-dead end trails have starting points searchable under POI-Attractions-Landmarks using keyword "Trail". All starting/ends points start with "Trail" for easy searching. The map is routable and many times take you via trails seeing I made them principle highway category. Also includes many off-road parks locations.
Some roads/trails may be closed so use your best judgement when riding.
The map is finished as far as I can make it. If anyone has gpx files of legal trails in their area that can be added PM me. Many trails are hand drawn using Google Earth and may be off by a few yards, but generally accurate.
The only ORV routes in Michigan that have a number system is on Drummond Island. Orange diamonds are snowmobile trails and may not necessarily be legal for ORV travel. ORV routes and ORV trails currently use orange triangles but will be switching to a totally new type of marker in the next few years.
Paul - 2005 Wrangler Unlimited