There are many 4x4 trails open to public use, though some specific trails require a trail permit. While many 4x4 trails are free of charge, these are commonly trails created on private property or land owned or leased by a 4x4 club. These trails can also be situated on government-owned property in certain situations, however, trails operating on most government land — be it state, county or federal property — require the purchase of a trail permit. Fees for these permits are often used for upkeep and maintenance of the trails as well as police patrol to ensure safety and rescue when needed.
On 4x4 trails requiring a permit, the permit is commonly required to be displayed prominently on the vehicle. The permits are often the same for a 4x4 vehicle as for an off-road motorcycle, dune buggy or all-terrain vehicle (ATV). Land set aside for use by off-road vehicles by any government entity is typically not sponsored by any federal or local monies beyond what the sale of the permits generate. These 4x4 trails require monitoring by law enforcement and maintenance crews in order to maintain a clean and safe environment for those who use them.
The vast majority of 4x4 trails requiring a permit are commonly posted very clearly with information. If you encounter a trail that is not so designated, it is often a wise habit to inquire at a local police department or ask a conservation or park ranger about the permit requirement. Not seeing a posting sign is not a valid excuse for failing to display a permit sticker on 4x4 trails and could result in a citation. The cost of the infraction is commonly in excess of the cost of a trail permit, and a permit will still need to be purchased in order to travel the trails in the future.
Many 4x4 trails are often subject to the "tread lightly" credo where the land is not to be disturbed any more than absolutely necessary under penalty of law. By monitoring the vehicles entering the trail site, any resulting damage can often be traced to the proper offender. This is aided by registering and tracking trail permit numbers and the time of entrance and departure for any given vehicle correlating with the reported trail damage. In most cases, the permits function like license plates for the vehicles traveling the 4x4 trails.