I know there are a lot of people on here who are confused about trail ratings I know I was. I found this on a website and thought I would post it up.
Taken from here
The ratings break into three broad categories: 1-4 is “easy” and may allow 2wd passage; 5-7 is moderate and requires 4wd, stock usually okay; 8-10 is difficult to extreme and requires special equipment, experience, and even then, may be impassable. The descriptions below are verbatim from the above website. The photos are mine with some commentary as well. I encourage you to follow up on the above link and all their sub-links; it's good reading and well done.
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.
Road rating 1 (Kaibab Plateau AZ)
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.
Road rating 2 (Blue Peak AZ)
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.
Road rating 3 (Scrub UT)
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.
Road rating 4 (Maple AZ) - Very rocky road, volcanic pumice boulders.
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.
Road rating 5 (Scrub UT) - It looks okay but this road is steep!!!
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.
Road rating 6 & 7 (Turtle AZ) - The road seen here is very steep, rocky and exposed - probably class 6 by this system. At the bottom is a stream crossing, definitely 12-18" deep, 30 feet across, moderate movement.
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.
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.
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.
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.
(If anyone wants to attach their pictures for examples of roads rated up to 10, feel free to do so. I usually can't or won;t drive anything that severe)
The authors of these ratings stress that these ratings can vary depending on the type of vehicle, whether the vehicle is stock or has special equipment (and what kind), the experience of the driver and the recent weather.
This article is for informative purposes only. I am not suggesting we adopt this wholesale, but it does give some framework within which to judge roads on an objective basis. Even if an author calls a road “4-5”, this is a big improvement over simply saying “passable by 4wd” when it is clearly not, or some other inaccurate over-generalization.
In my reports I have tried to be descriptive about the quality of the roads, and tend (at least I think so) to be conservative as to whether a call a road 4wd, erring on the side of caution. I am one of those people who will use the 4wd option (I have a stock 2001 Nissan Frontier truck) if I think there may be rough stuff ahead, even if the road now is fine by 2wd.
The motivation for this article stems from a hike I did with two others a year ago in Arizona. We were using a very scant personal report from a previous visitor who simply stated “drive the roads to …”, neglecting to mention the roads were pretty rough, steep, remote and involved a large stream crossing. We ended up using more time on the roads than we’d planned.
To each their own. Some of you like not knowing and hoping for the best. Others like to plan accordingly, with at least some idea of what to expect to build that into the overall time framework.