Lots of different ways to rate trails when you goggle 4x4 trail rating systems.
The ones I have found are the best are in the 4 x 4 guide books for your area, since they describe the actual trails you may want to seek out. I live in Southern California and Charles A. Wells has a number of great trail guide books such as "Guide to Moab, UT Backroads and 4-Wheel Drive trails". Each is rated by his easy, moderate and difficult rating system. Plenty of verbiage with directions, GPS points and photos of each of his trail recommendations. He has other books for So Cal, Nor Cal, Ariz, Nor Colo and Colo overall. I'm not sure where you live, but other guide books for other parts of the country are available, and often have a rating system of sorts. Some are written by some colorful charters, who obviously have a lot of local experience.
I'm sort of embarrassed to be talking about guide books like some kind of tourist. But when we drove from So Cal to Flagstaff, AZ we know nothing about the local area and we quickly found from the book what the pics below show.
When we go to Moab in the spring, we will have the guide, and want to go straight to the trails that seem right for us. A well thought out trail rating system and guide for the area can be a real help.
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