This is the system used by californiajeeper.com.
|1-3||1-3||feature trails with obstacles that are easy to navigate. In optimum weather conditions, some of these trails may not require the continual use of four-wheel drive (4WD).|
|4-7||4-7||are moderately demanding trails on which 4WD is required. You may encounter a wide variety of challenges, including mud holes, boulders, and stream crossings, on the trail.|
|8-9||8-9||indicate that the likelihood of getting stuck is considerably higher. Mud holes here may be deep and rock climbing will be more arduous.|
|10||10||is reserved for the most demanding off-road trail in the Northern California—the Rubicon Trail.|
Note: Trail ratings are highly subjective. A trail that is easy for an experienced driver with a highly modified vehicle may be impassable for a novice driver in a stock vehicle. Weather conditions may also significantly affect the difficulty of a trail. Also, the difficulty of a trail may change over time, as trail use, weather, and maintenance modify the trail. Always check with the managing organization and/or recent users before planning a trip on a trail and scout ahead on foot if you are not sure of current conditions.