Class 1: Corvette. Paved or very good graded dirt or gravel roads. Suitable for any highway-legal vehicle.
Class 2: Toyota Camry. Gravel or dirt road with some rocks, bumps and/or washboard. Suitable for any normal-clearance passenger vehicle.
Class 3: Subaru Forester. Rough gravel, dirt or rock road with bumps, steps or water crossing that make it challenging for typical passenger cars, and better suited for light-duty SUVs with at least medium ground clearance.
Class 4: 4WD Pickup or SUV. Very rough or otherwise challenging rock or dirt road typically requiring one or more of the following: 4WD, high clearance, off-road tires, slow speed and basic off-road driving skills. May include deep ruts, high steps, cambered roadways, large loose rocks, and/or significant water crossings.
Class 5: "Wheeling" Jeep, etc. Class 5 can be broken out into subclasses: 5.1, 5.2, 5.3 and so on. All Class 5 roads are suitable for high-clearance, 4WD vehicles with off-road tires. Driving with lesser equipped vehicles may be possible, but damage to the vehicle is much more likely, and off-road driving skill and road-building skills are likely to be required.
There are several factors that make a road challenging. Where one of these is a major contributor to a road rating, it is listed after the class rating.
- Loose rocks
- Rock steps
- Mud (includes slippery clay)
- Steep (climbs or descents)
- Exposure (as in rock climbing, exposure to what appears to be a long drop)
- Water crossing
- Obstacles (e.g. fallen logs)