Trail Rating Systemprovided by: Colorado Association of 4 Wheel Drive Clubs.
Rating routes is a very challenging endeavor. The roads and trails themselves are constants, only changing when the wind, rain, or spring thaw dictates. The users of the roads and trails are the variables in the rating challenge. Some users are well equipped and well experienced with many challenges and successful trips under their belt. While on the other hand some users are new to the sport and may have stock vehicles with no modifications. And then there are all of the varying levels of operators and equipment in between. In order for anyone to successfully use a rating system to decide which roads to take you must first be honest with yourself about your ability, and the ability of your equipment.
If you are testing yourself and your equipment to learn your ability or to improve your ability, be prepared to admit defeat. Destroying your equipment and the route in the process to say you have driven a road or trail helps defeat those who are trying to keep these routes open for continued use. You can always return to an un-abused trail or road to try again.
A road or trail's rating comes from the worst spot that must be traversed. You could have a route 5 miles long with 4-1/2 miles being and easy 3, but the last ? mile may give the trail it's rating of 8.
Modify the numbers as follows-
If you drive a stock vehicle, normal open differentials, tires smaller than 30", or if you are an inexperienced Four Wheeler, add 1 to the number rating.
If you have Four Wheeling experience or are driving a vehicle equipped with posi-traction, aggressive tires, off-road suspension components, extra low gearing, etc. then you can subtract 1 from the rating.
Weather is important in a route's rating and can change it quickly. A normally dry section of road rated 5 can change to an 8 if it is turned to mud from a weeks worth of rain, or spring run-off, or if there is more than 6" of snow."
Level 1) Graded dirt road. Dry, or less than 3" water crossing depth. Gentle grades. 2WD under all conditions except snow. No width problems, two vehicles wide.
Level 2) Dirt road. Dry, or less than 3" water crossing depth. Some ruts. Slight grades, up to 10 degrees. 2WD under most conditions. Rain or snow may make 4WD necessary. Usually one and a half to two vehicles wide.
Level 3) Dirt road. Rutted, washes, or gulches. Water crossings up to 6" depth. Passable mud. Grades up to 10 degrees. Small rocks or holes. 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.
Level 4) Rutted and/or rocky road. No shelves but rocks to 9". Water crossings usually less than hub deep. Passable mud. Grades moderate, up to 15 degrees. Side hill moderate up to 15 degrees. 4WD under most conditions. No width problems, vehicle passing spots frequently available if less than two vehicles wide.
Level 5) Rutted and/or rocky road. No shelves. Rocks up to 12" and water crossings up to 12" with possible currents. Passable mud. Moderate grades to 15 degrees. 6" holes. Side hill to 20 degrees. 4WD required. No width problems.
Level 6) Quite rocky or deep ruts. Rocks to 12" and frequent. Water crossings may exceed hub depth with strong currents. Shelves to 6". Mud may require checking before proceeding. Moderate grades to 20 degrees. Sidehill may approach 30 degrees. 4WD necessary and second attempts may be required with stock vehicles. Caution may be required with wider vehicles.
Level 7) Rocks frequent and large, 12" and may exceed hub height. Holes frequent or deep (12"). Shelves to 9". Mud 8" deep and may be present on uphill sections. Grades to 25 degrees and sidehill to 30 degrees. Water crossings to 18" and may have strong currents. 1-1/2 vehicles wide. 4WD required. Driver experience helpful.
Level 8) Heavy rock and/or severe ruts. Rocks exceeding hub height frequent. 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. Side hill to 30 degrees. One vehicle wide. Body damage possible. Experience needed. Vehicle Modifications helpful.
Level 9) Severe rock over 15". Frequent deep holes over 15". Shelves over 15". Mud bog conditions (long, deep, no form bottom). Over 30" water crossings with strong currents. Steep grades over 30 degrees. Sidehill over 30 degrees. May not be passable by stock vehicles. Experience essential. Body damage, mechanical breakdown, rollover probable. Extreme caution required.
Level 10) Severe conditions. Extreme caution recommended. Impassable by stock vehicles. Winching required. Trail building necessary. May be impassable. Impassable under anything but ideal conditions. Vehicle damage probable. Personal injury possible. Extreme caution necessary.