The Numeric Scale: 1 — 10
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.
- Improved / graded dirt with gentle grades road passable by 2WD vehicles under all conditions except snow. No width problems for two vehicles to pass.
- Dirt road with slight grades and some ruts. Dry, or less than 3" water crossing depth. Passable by 2WD vehicles under most conditions. Rain or snow may make 4WD necessary. Usually one and a half to two vehicles wide.
- Dirt road with ruts, washes, or gulches. Dirt, sand and rock surfaces, with mud holes possible. 4WD recommended but 2WD possible under good conditions and with adequate ground clearance and skill. No width problems for any normal vehicle. Vehicle passing spots frequently available if less than two vehicles wide. Maybe impassable when wet due to soil composition.
- Road surface consisting of loose rock, dirt with erosion, washes, gulches and rocks and steps from 7" to 12". Water crossings usually less than hub deep and passable mud. Moderate grades and side hills up to 15 degrees. 4WD is recommended with good ground clearance and driving skills. Aggressive tires and limited slip would be a plus. No width problems with vehicle passing spots frequently available if less than two vehicles wide.
- Road surfaces are rocky, rutted and/or sandy with rocks and ledges up to 12/14". Water crossings up to 12" with some mud possible. Moderate grades to 15 degrees and side hills to 20 degrees. Good 4WD vehicle required with tall tires and traction added device (lockers, limited slips) is recommended. Above average driving skills are desirable. Reasonable trail width for all vehicles.
- Roads are difficult and quite rocky and/or scarred with deep ruts. Moderate grades to 20 degrees and sidehills may approach 30 degrees. Water in excess of 12" is possible with mud conditions. Tall tires (33" plus) with traction added devices (lockers, limited slips) are recommended. A winch would be a plus. Enhanced suspension travel and ground clearance are helpful. Above average driving skills are recommended. Caution may be required with wider vehicles.
- Trail consists of rocks, frequent and large and may exceed hub height. Holes also frequent or deep (12"). Steep inclines and declines are prevalent. Enhanced off road equipment is required including locking devices (front & rear), tall tires, maximum vehicle ground clearance, and tow hooks. A winch is desirable. Excellent driving skills are required. Vehicle mechanical or body damage is possible. Roll over possibilities may exist. Excellent driving skills are recommended.
- Trail consists of heavy rocks and/or severe ruts. Rocks exceeding hub height are frequent as may be shelves to 12". Deep mud or uphill mud sections. Steep grades to 25 degrees and can be loose or rocky. Water crossings may exceed 30" in depth and side hills up to 30 degrees. Enhanced off road equipment is required including locking devices (front & rear), tall tires, maximum vehicle ground clearance, and tow hooks. A winch is desirable. Excellent driving skills are required. Vehicle mechanical or body damage is possible. Roll over possibilities may exist. Excellent driving skills are recommended. One vehicle wide.
- Extreme caution is required. Trail has severe rocks and shelves over 15" and frequent deep holes over 15". Trail may have mud bog conditions (long, deep, no form bottom) and/or over 30" water crossings with strong currents. Steep grades over 30 degrees and sidehills over 30 degrees. Beyond the capability of most stock vehicles. Experience essential. Body damage, mechanical breakdown and rollover probable. Excellent driving skills are required. Winches, spare parts and tools are recommended. Be prepared to spend the night on the trail.
- Severe trail conditions. Extreme caution recommended. Winching may be required. Trail building may be necessary. May be impassable under anything but ideal conditions. Vehicle damage probable and personal injury possible. Impassable by stock vehicles. Street driven 4X4's should not attempt this trail.