Trail raiting description start at 2
riped from another online offroad club (azvjc.org) :
+ A plus sign by the trail rating indicates that this trail will have obstacles that are more difficult, and/or have many obstacles. For instance, a "4+" will be Difficult 4WD trail with many 4.0 rated obstacles and some optional 4.5 rated obstacles.
- A minus sign by the trail rating indicates that this trail will be less difficult, and may have only a few obstacles. For instance, a "3.0-" trail will be mostly a Easy 4WD trail with one or two non-optional obstacles that are more challenging
2: Easy 2WD/4WD: Features trails with obstacles that are easy to navigate. In optimum weather conditions, these trails may not require the continual use of four-wheel drive (4WD).
2.5: Easy 4WD: Moderately demanding trails on which 4WD will be required. You may encounter a wide variety of challenges (Potholes, minor washouts, medium size rocks, and mud holes) on these trails. Higher ground clearance and Off-Road tires are recommended.
3: Standard 4WD trail: Demanding trails on which 4WD is required. You will encounter a variety of more difficult challenges (loose rocks, large potholes, steep inclines, and large rocks) on these trails. Possible with stock 4WD vehicle, however, recommend traction device (limited slip) in rear differential, aggressive tread and low air pressure. Higher than stock ground clearance is advisable. Low range gears used often. Moderate experience and driving skill advised. Likely paint damage, possible rocker-panel damage.
3.5: Challenging 4WD trail: Challenging trails on which low range 4WD is required. You will encounter a variety of more difficult challenges (loose rocks, large potholes, steep inclines, and large rocks) on these trails. Not recommended with stock 4WD vehicle. Traction device (limited slip) in rear differential, aggressive tread and low air pressure highly recommended. Higher than stock ground clearance is advisable. Moderate experience and driving skill advised. Likely paint damage, possible rocker-panel damage.
4: Difficult trail: These trails traverse very rugged terrain; low-range 4WD is required. Higher than stock ground clearance is required. Aggressive tread and low air pressure are required. Traction Devices (Lockers or limited-slip) in the differentials (front and rear), lift, and larger tires are highly recommended. These trails require above average Off-Road driving skills. High-Lift jacks and winches would also be helpful. There will likely be paint damage and possible vehicle body and/or mechanical damage.
4.5: Extreme trail: These trails cross extremely rugged terrain with very steep inclines, large boulders, and potentially dangerous situations. These trails require modified vehicles, including lift, lockers, and over-sized tires. A High level of Off-Road driving skill is required. There will likely be paint damage, possible vehicle body and/or mechanical damage. There are possibilities of rollovers. Winches are recommended.
5: Impassable trail: These trails are for the extreme four-wheeler only. These trails require highly modified vehicles, including lift, excellent articulation, lockers front and rear, large tires with aggressive tread, winches, high lift jacks. A High level of Off-Road driving skill is required. Paint damage is virtually guaranteed, body and/or mechanical damage is very likely. Rollovers will be more common on these trails and a winch will be used on at least one obstacle.