These are not definitive for all trails and OHV areas. There are at least 3 sets of ratings that I have seen in use: 1-10 Scale; 1-5 Scale; and Color/Picture codes. You can usually find specific trail rating guides for the area that you plan to visit. For example, Utah.com has their own page for the Moab trails and you can check JeepJamboreeUSA.com for the scale for their events.
- Rutted dirt or rocky road suitable for most SUVs with some obstacles that will require careful tire placement. Four-wheel drive, low range gears and high ground clearance required. Skid plates and tow hooks are recommended on most trails. Some fairly steep grades and soft sand possible. Some areas will have sideways tilt that will require caution. Trail will not always have room to pass - backing up may be necessary. Brush may rub vehicle. Water depths passable for stock high clearance vehicles except during periods of heavy runoff. Mud holes likely in the spring.
- Gravel, dirt, clay, sand or mildly rocky roads with gentle grades. Water levels low except during periods of heavy runoff. Wide enough for a single vehicle and usually wide enough to pass another vehicle on the trail. Minimum sideways tilt. Four-wheel drive recommended on most trails. Some clay surfaces may be impassable when wet. These trails or fire roads provide a good starting point for beginners.
- Some trails are suitable for more aggressive stock vehicles but most will require vehicle modification. Suspension lifts, differential lockers, aggressive articulation and/or winches recommended in many cases. Skid plates and tow hooks are highly recommended. Steep grades with severe ground undulation. Sideways tilt can be extreme. Body damage is possible. Brush may scratch sides of vehicle. Deep water crossings possible. Shelf roads can be extremely narrow - use caution in full-size vehicles. Passing may be difficult and require backing for long distances.