Off-roading is the activity of driving or riding in a vehicle on unpaved surfaces such as sand, gravel, riverbeds, mud, snow, rocks, and other natural terrain. Types of off-roading range in intensity, from leisure drives with unmodified vehicles, to competitions with customized vehicles and professional drivers. Off-roaders have been met with criticism for the environmental damage caused by their vehicles. There have also been extensive debates over the role of government in regulating the sport, including a Supreme Court case brought against the Bureau of Land Management in the United States. Off-road vehicle Travelling over difficult terrain requires vehicles capable of off-road driving such as ATVs. These vehicles have features designed specifically for use in off-road conditions such as extended ground clearance, off-road tires and a strengthened drive-train. Some manufacturers offer vehicles specifically designed for off-road use. Recreational off-roading Some examples of recreational off-roading include the following: Dune bashing Dune bashing is a form of off-roading on sand dunes. A large sport-utility vehicle such as the Toyota Land Cruiser is used (however, light weight vehicles often fare better in the extremely soft sand found on sand dunes). Vehicles driven on dunes may be equipped with a roll cage in case of an overturn; Similar to auto-racing, experience and skill is required to maneuver the car and prevent accidents. Before entering the desert in an everyday-use SUV or pickup, it is essential to reduce the tire pressure. This is done to gain more traction by increasing the footprint of the tire and, therefore, reducing the ground pressure of the vehicle on the sand as there is a greater surface area (much like a person wearing snowshoes can walk on a soft surface without sinking, but a person without them cannot). For example, tires with a recommended pressure of 35 psi would be reduced to approximately 12-15 psi. A common modification is to fit bead lock rims, which allow tire pressure to be lowered even further, without risking tire and rim separation. Upon entering the desert, it is common to meet with a pack of vehicles and a group leader before proceeding. The group leader then leads the pack through the stunts in single file. The main reason for this technique is to prevent vehicles from losing track of direction and getting lost. Off-road racing Desert racing High-speed racing in the open desert includes chases and racing on a rough desert terrain