This system is described on AZ Rockcrawler.com. More details, including reasons for developing the system and recommended equipment for different size vehicles, can be found here.
|1.0||1-2||Improved dirt road|
|2.0||3-4||Unimproved dirt roads. Potholes, minor wash outs, medium sized rocks and mud holes. Higher ground clearance helpful.|
|3.0||5||Difficult Trail. Loose gravel, large pot holes, steep inclines, medium sized rocks, 4 wheel drive required, aggressive tread and lowered tire pressure helpful. See the list of recommended parts to carry.|
|3.5||6||Hard Trail. Same as above. Some rocky sections, go arounds at major obstacles. Body damage possible, mainly rocker panel or rear quarter panel.|
|4.0||7||Moderate rocky trail. Frequent ledges, crevices, large boulders, steep inclines and off camber situations. Body and or tire damage likely. Spotters may be needed for some obstacles. Low tire pressure required, good chance of loosing a bead. Possible component breakages.|
|4.5||8||Hard rocky trail. Same as a 4.0 rated trail but the obstacles are bigger, tighter squeezes and bigger risks to body and mechanical components. Few bypasses if any. Longer wheelbase vehicles may have problems with breakover angles, short wheelbase vehicles may have to use a winch or strap on some obstacles. Large vehicles will damage sheet metal. Spotter may be needed for all major obstacles. Rollovers possible. Plan for common component breakages (vehicle specific).|
|5.0||9||Extreme rocky trail. Same as a 4.5 rated trail but the obstacles are bigger, tighter squeezes and bigger risks to body and mechanical components. No bypasses. Body damage guaranteed. Spotters needed for most of trail. Rollovers likely. Some obstacles may require a winch for larger vehicles. Trail may be impassible when wet. Plan for major component breakages. Realistically these trails should be run with rock buggies.|
|5.5||10||Insane trail. Same as a 5.0 rated trail except all of the obstacles are bigger. Constant spotting required, vehicles will get hung up frequently, undercarriage will catch rocks. At some point a winch will be required to support the full weight of the vehicle.|
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.