OHV use in the parks has been particularly contentious, although NPS has fewer lands open to OHVs than do other federal land management agencies such as the Bureau of Land Management (BLM) and the Forest Service (FS). 819 , H.R. 2954 , and S. 486 , all of which would change regulations for OHVs at Cape Hatteras National Seashore; and H.R. ATVs and Oversand Vehicles15

Excluding Alaska, 13 NPS units allow off-road use of ATVs, four-wheel drive vehicles, and/or dune, sand, and swamp buggies by the general public. NPS is in the process of issuing special regulations to designate routes and areas for off-road use in those units that permit ATVs and oversand vehicles. The extent of unauthorized OHV use in the National Park System is unclear. Snowmobiles45

Proposals to regulate recreational snowmobile use in NPS units have been controversial, with debate often mirroring the preservation/use conflict within the NPS mission. Site-Specific Conflict: Yellowstone National Park

Since 2000, regulatory and judicial actions to restrict or allow snowmobile use have been park-specific, centering on Yellowstone National Park and units near it, including the John D. Rockefeller Jr. Memorial Parkway and Grand Teton National Park. Both plans, as well as most subsequent revisions, were vacated by different federal courts. The regulations allow up to 110 transportation events per day, defined as the use of one snowcoach or one group of an average of seven snowmobiles. Some snowmobile user groups, as well as some environmental groups, have also expressed support for the plan. Aircraft overflights are also a concern for other park units. Site-Specific Conflict: Grand Canyon National Park

Several actions have been taken to achieve the substantial restoration of natural quiet at Grand Canyon in furtherance of P.L. Third, the FAA issued a final rule establishing a standard for quiet technology for certain aircraft in commercial air tour operations over Grand Canyon. NPS is continuing to assess the provisions to determine how they will affect its planning effort. 112-141 , which contains provisions on air tour management at Grand Canyon. The 112 th Congress enacted broad aviation legislation with provisions affecting commercial air tours over park units generally ( P.L. 112-95 ). The provisions seek to expedite and streamline agency actions, in part because of the slow progress in completing ATMPs. Another provision of P.L. Subsequently, P.L. Recent controversies have focused on regulatory actions that would restrict recreational use of or access for these vehicles, often in specific park units. The court ordered NPS to re-evaluate environmental assessments justifying PWC use, but did not vacate or overturn the current rules allowing them. General NPS Rule

On July 6, 2012, NPS finalized a rule broadly addressing mountain bicycles within NPS units. Site-Specific Actions

Currently, more than 40 NPS units allow mountain biking on dirt trails and/or dirt roads. Conclusion

Motorized recreation on NPS lands sometimes brings into conflict the two parts of the NPS mission: to conserve public land while at the same time providing for its enjoyment by the public. In NPS units that permit ATVs; dune, sand, or swamp buggies; snowmobiles; aircraft overflights; personal watercraft; and/or mountain bikes, the desire for access to these recreational opportunities has clashed with concerns about resource damage and disturbance of non-motorized pursuits. NPS's laws, regulations, and policies generally emphasize the conservation of park resources in conservation/use conflicts, and NPS has fewer lands open to off-highway vehicles than do other federal land management agencies such as the Bureau of Land Management and the Forest Service. The 113 th Congress has addressed motorized recreation in the National Park System through legislation and oversight.
In managing its lands, the National Park Service (NPS) seeks to balance a dual statutory mission of preserving natural resources while providing for their enjoyment by the public. Motorized recreation on NPS lands sometimes brings the two parts of this mission into conflict. Off-highway vehicles (OHVs) have been particularly controversial, with calls for greater recreational access intersecting with concerns about environmental impacts and disturbance of quieter pursuits. NPS's laws, regulations, and policies generally emphasize the conservation of park resources in conservation/use conflicts, and NPS has fewer lands open to OHV use than do other federal land management agencies such as the Bureau of Land Management and the Forest Service. The 113th Congress has addressed motorized recreation through legislation and oversight, concerning broad issues such as recreational access to federal lands as well as individual conflicts at specific NPS units.
ATVs and Oversand Vehicles. Only 13 of the 401 park units are open to public recreational use of all-terrain vehicles (ATVs), four-wheel drive vehicles, and/or dune, sand, and swamp buggies. The extent of unauthorized use of such vehicles is in dispute. Several units have developed pilot education and deterrence programs to address unauthorized use. Legislative measures in the 113th Congress (H.R. 819, H.R. 2954, S. 486) seek to regulate OHV use at one NPS site, Cape Hatteras National Seashore.
Snowmobiles. Regulatory and judicial actions to allow or restrict snowmobile use have focused primarily on three Yellowstone-area park units. Winter use plans developed by NPS to establish numerical limits on snowmobile and snowcoach entries have been the subject of repeated, and often conflicting, court challenges. Most recently, NPS issued a final rule governing snowmobile use at Yellowstone for the 2014-2015 winter season and beyond. The rule allows up to 110 "transportation events" per day (defined as the use of either a multipassenger snowcoach or a group of snowmobiles).
Aircraft Overflights. Grand Canyon National Park is at the center of a conflict over whether or how to limit air tours over national park units to reduce noise. NPS and the Federal Aviation Administration (FAA) continue to work to implement a 1987 law (P.L. 100-91) that sought to reduce noise at Grand Canyon, and a 2000 law (P.L. 106-181) that regulates overflights at other park units. P.L. 112-141, enacted in 2012, contains provisions on air tour management at Grand Canyon, including some less-stringent standards for natural quiet than NPS had recommended in planning efforts. P.L. 112-95 contains provisions to expedite and streamline agency planning actions for commercial air tours over parks generally.
Personal Watercraft (PWC). Since 2003, NPS has completed regulations to open designated PWC areas at 13 units. In 2010, a federal judge ordered NPS to re-examine environmental assessments justifying PWC use at two of those units but did not overturn existing regulations.
Mountain Bicycles. This mechanized though nonmotorized activity also raises issues of the sufficiency of access to park lands as well as potential resource damage and disturbance of quieter recreational pursuits. Currently, more than 40 NPS units allow mountain biking on dirt trails and/or dirt roads. Mountain biking advocates have worked with NPS to explore opportunities to increase this activity in park units. In 2012, NPS finalized a rule that eases the process for park superintendents to open trails to bicycles.