Winter Use Management

a group of snowmobiles and a large yellow snowcoach passing a group of bison a snowy road
Snowmobiles and a snowcoach passing a group of bison on a park road.

The National Park Service (NPS) mission is a dual mandate: preserve Yellowstone’s resources and make the park available and accessible for enjoyment and appreciation. The ways in which visitors access Yellowstone in winter can affect the park’s plants, animals, and wild character in ways more profound—and potentially more damaging–than at other times of the year. To meet its mission, the NPS has worked carefully to develop a long-term plan for winter use in Yellowstone that both protects the park’s resources and provides outstanding opportunities “for the benefit and enjoyment of the people.”

NPS Regulation 36 CFR 2.18 prohibits snowmobile use in national parks when there is no specific rule authorizing their use. This is known as the “closed unless open rule”— without a specific rule, oversnow vehicles would be prohibited from entering Yellowstone.


Our Goals

For years, the NPS managed the park in winter with interim management plans in the face of repeated courtroom challenges over snowmobiles and other winter operations. The final rule, published in October 2013, concluded more than 15 years of planning efforts and litigation, addressed concerns raised by the public (overcrowding, impacts on natural resources, noise and air pollution, availability of facilities/services, snowmobile restrictions, importance of winter visitation to the economy, wildlife using groomed roads, displacement of wildlife, and health and human safety), and established long-term management of winter use in Yellowstone.

We work to provide a high-quality, safe, and educational winter experience.

We work to provide for visitor and employee health and safety.

We will protect wilderness character and values.

We will preserve pristine air quality.

We will preserve natural soundscapes.

We will mitigate impacts to wildlife.

We will coordinate with partners and gateway communities.

three photos side-by-side showing oversnow travel on park roads
From left to right: (1) Xanterra Bombardier snowcoaches at Swan Lake Flat; (2) A commercially guided snowmobile group passing bison near Lower Geyser Basin; (3) A snowcoach and group of bison along the Madison River.

Winter Use Management in Yellowstone

NPS Regulation 36 CFR 2.18 prohibits snowmobile use in national parks when there is no specific rule authorizing their use. This is known as the “closed unless open rule” — without a specific rule, oversnow vehicles would be prohibited from entering Yellowstone. The final Rule authorizing OSV use in Yellowstone was published in the Federal Register on Oct. 23, 2013, and was based upon the environmental analyses contained within the 2012-2013 Supplemental Environmental Impact Statement (SEIS) and Record of Decision. The final Rule provides mechanisms to make the park cleaner and quieter than previously authorized; provides greater flexibility for OSV commercial tour operators; rewards new oversnow technologies; and allows for increases in public visitation.

The specific parameters established by the final Rule for winter use in Yellowstone are:

  • Up to 110 daily transportation events.
  • 46 reserved for commercially guided snowmobiles.
  • 4 reserved for non-commercially guided snowmobiles.
  • No less than 60 events reserved for snowcoaches.
  • New "best available technology" (New BAT) is required for snowmobiles by December 2015. Under New BAT, snowmobile transportation events can be up to 10 snowmobiles in a group, with group size averaging seven each winter.
  • BAT is required for all snowcoaches by December 2016, sooner for newer models.
  • Voluntary "Enhanced BAT" (E-BAT) certification will allow commercial tour operators to increase the average numbers of snowmobiles in their groups from seven to eight and snowcoaches from one to one-and-a-half across the season.
  • One non-commercially guided group of up to five snowmobiles is permitted to enter through each of the four park entrances every day.
  • OSV's may continue to use Sylvan Pass; however, the pass may be closed at any time due to avalanche danger or mitigation efforts.
  • Park managers are collaborating with the public by implementing an Adaptive Management Program, which will combine science with public input, to ensure that OSV use impacts stay within limits predicted in the final Plan/SEIS.
a large yellow snow bus on a snowy road near bison
A snowcoach near the Madison River and bison.

Adaptive Management Program

The final Rule in 2013 authorized an adaptive management program to inform and improve winter use management. Adaptive management is a three-step process: management, monitoring, and evaluation, which improve resource protection by blending science and public engagement. It enables natural resource managers to acknowledge uncertainties in the management of natural systems and respond to changing conditions while working with the public and interested stakeholders. Collaborative adaptive management, the approach Yellowstone is taking, emphasizes joint learning and an active partnership between managers, scientists, and other stakeholders, including the public.

The objectives of the program are to:

  • Evaluate the impacts of OSV use and help managers implement actions that keep impacts within the range predicted under the final Plan/SEIS.
  • Gather additional data to compare impacts from a group of snowmobiles versus a snowcoach.
  • Reduce impacts on park resources after implementation of the final Rule by gathering additional data on the overall social and ecological impacts of winter use.

To meet these objectives, the NPS collaborated with the public and other partners to develop a long-term, sustainable adaptive management plan for winter use in Yellowstone National Park. This plan outlined a process for public engagement and for prioritizing indicators to address scientific uncertainty and monitor resources of interest. NPS staff released the final adaptive management plan for winter use to the public in December 2016. Public input was included through participation in the Adaptive Management Team and the Adaptive Management Working Group. Meetings were also held throughout the region and were available remotely via webinar.

Adaptive Management Team

The winter use Adaptive Management Team is the broader public engagement body that encompasses all working groups and will provide feedback on the overall implementation of the Adaptive Management Program, including Adaptive Management Plan drafts. The Team focuses on the Adaptive Management Program in its entirety, and meets regularly to coordinate across impact topics, and to provide feedback to the NPS on Adaptive Management Program operations. The team also discusses the results of monitoring, how those results are related to the impacts that were described in the final Plan/SEIS, and, if warranted, discuss potential, adaptive changes that may be considered by the NPS. The team is composed of the Adaptive Management Program Coordinator, all working group leads, working group participants and other interested parties.

Adaptive Management Program Working Groups

The NPS is asking for feedback from working groups, made up of interested stakeholders and citizens, to develop a long-term and sustainable winter use Adaptive Management Plan (AMP), which will guide the park's future data collection on the impacts of winter use. Working groups are sub-groups of the larger adaptive management team, which meets to discuss ideas across topics and provide feedback on the overall AMP process.

The working groups focus on five impact topics: wildlife (suspended in winter 2021-2022), air quality and soundscape, human dimensions, operations and technology, and the non-commercially guided snowmobile access program. Each working group develops a monitoring strategy for its impact topic in coordination with an NPS subject-matter expert. Specifically, working groups are tasked with providing feedback on what resource or impact questions should be monitored to address key scientific uncertainties about their impact topic, and on how to design a fiscally sustainable, efficient, and feasible monitoring strategy to achieve key monitoring objectives going forward. Park managers then use the results of winter use monitoring and stakeholder input to make decisions that best protect park resources and the visitor experience.


The Wildlife Working Group made recommendations to the NPS on the design of an updated monitoring strategy that measured and evaluated the impacts of winter use on the park's wildlife species, including bison, trumpeter swans, elk, lynx, wolverines, gray wolves, and bald eagles to ensure winter wildlife ecology was not disrupted going forward. This group also provided feedback to the NPS on current and future results of wildlife monitoring and research, and on adaptive management actions that may be implemented in the future as part of the new Adaptive Management Plan. Because wildlife evaluations did not substantially change over a decade, the wildlife monitoring effort was suspended in winter 2021-2022.

The Soundscape and Air Quality Working Group make recommendations to the NPS on the design of an updated monitoring strategy that measures and evaluates the impacts of oversnow vehicle use on the park's natural soundscape and on the park's air quality to ensure a cleaner and quieter park, and compliance with the new winter use sound and air emissions requirements.

The Human Dimensions Working Group make recommendations to the NPS on the design of an updated monitoring strategy that 1) measures and evaluates the impacts of winter use on the visitor experience, and other relevant publics, and 2) assesses changes in winter visitation under the new winter use plan and how such changes impact park resources.

The Operations and Technology Working Group make recommendations to the NPS on the design of an updated monitoring strategy that measures and evaluates how winter use operations, under the transportation event concept, and oversnow vehicle technologies can be improved or modified to create a cleaner and quieter park experience, to facilitate cleaner-running vehicles and to generally reduce impacts to park resources.

The Non-Commercially Guided Snowmobile Access Program permits people to snowmobile in Yellowstone without the presence of a commercial guide. Up to four non-commercially guided groups are allowed to enter the park daily: one group at each oversnow entrance.

two people riding snowmobiles on a snowy road
Two non-commercially guided snowmobilers on a snowy park road.

Questions & Answers


Recent studies on winter use indicate park resources are in very good condition. Research shows that snowmobiles and snowcoaches contribute similarly to the impacts of winter use. The perception that snowmobiles contribute to the vast majority of observed effects, and that those effects would greatly diminish by limiting travel to snowcoaches only, is not supported. When managed, both modes of transportation provide opportunities for visitors to enjoy the park. Each can offer different experiences for visitors, just as cross-country skiing, snowshoeing, and walking offer different opportunities for visitors to enjoy the park in the winter.


The impact of oversnow vehicles (OSV) on wildlife is a key issue in winter use policies. OSV's are required to stay on groomed roads, but the roads are often situated where wildlife may concentrate in winter. Research indicates that disturbance by winter visitors is not a primary influence on the distribution, movements, or population size and composition of bison, trumpeter swans, elk, coyotes, and bald eagles.

Monitoring OSV use in Yellowstone shows that nearly all OSV users remain on groomed roads and behave appropriately toward wildlife, rarely approaching unless animals are on or adjacent to the road. In most of 7,603 encounters observed between people on OSV's and wildlife, the animals either had no apparent response or looked and then resumed what they were previously doing.

Road grooming does not increase bison migration out of the park. Data on bison road use and off-road travel collected from 1997 to 2005 found bison on the road less often from December to April when the roads were groomed than during the rest of the year, and no evidence that bison preferentially used groomed roads during winter.

Compared to similar studies done in other places, the relatively low intensity of wildlife responses in Yellowstone suggests that because the encounters near roads are predictable and apparently not harmful to the animals, some habituation to OSV's and associated human activities may be occurring.

Making all visitors use a guide has nearly eliminated wildlife harassment. Guides enforce proper touring behaviors, such as passing wildlife on or near roads without harassment and ensuring that wildlife do not obtain human food. Monitoring indicates that snowcoaches have a slightly higher probability of disturbing wildlife than do snowmobiles.

Air quality

Winter air quality in Yellowstone depends primarily on proximity to roads, parking areas, employee housing, and visitor lodging. Although visitation is far lower in the winter than in the summer, OSV's produce more emissions. Prolonged exposure to air pollutants such as carbon monoxide (CO), fine particulate matter (PM <2.5 micrometers), and hydrocarbons can pose health risks.

Levels of carbon monoxide and particulates fell dramatically after 2002 with conversion to BAT snowmobiles and reduced OSV numbers. Hydrocarbon and air toxic concentrations are also no longer a concern, with the possible exception of formaldehyde and benzene levels, which are being closely monitored. Carbon monoxide and particulate matter are monitored at the West Entrance and Old Faithful, where OSV's are most concentrated. BAT snowmobiles and snowcoaches produce a similar amount of air pollution on a per passenger basis. Under the Clean Air Act Amendments of 1977, Yellowstone is one of 156 national parks and wilderness areas that are designated Class I airsheds, requiring the most stringent protection.


Noise levels have also fallen somewhat with the conversion to BAT snowmobiles, mandatory commercial guiding, and limited numbers of snowmobiles. Although snowmobiles and snowcoaches are commonly heard during certain periods of the day, their noise is absent during other time s— even in developed areas like Old Faithful and along busy corridors like the West Entrance Road.

Oversnow vehicles are audible 61% of the day at Old Faithful and 51% of the day at Madison Junction, per the 2010–2011 monitoring report, down from 67% and 54%, respectively. (National Park Service vehicles account for approximately one-fourth of this noise.) The BAT requirements for snowcoaches, implemented in 2016, reduced noise even more. Snowcoaches account for 94% of the loud oversnow vehicles. Guided snowmobile groups and snowcoaches contribute nearly equally to the percentage of time oversnow vehicles are heard.


With guiding has come a 50% reduction of law enforcement incidents, even when accounting for the drop in visitation. Arrests have virtually disappeared. Calls for medical assistance are the only statistic that has increased since the conversion to mandatory guiding.


More Information

Bombardiers make their way through the rocky formation called the Hoodoos on the way to Mammoth.
History of the Debate

Winter use planning is one of the most contentious issues for park managers and visitors with the debate spanning more than 80 years.

two park rangers inspecting the wing of a small bird
Science Publications & Reports

View science publications and reports created by Yellowstone's Center for Resources on a variety of park topics.

A snow-covered evergreen tree sits in the foreground of visitors on a wooden boardwalk amongst steam
Explore in Winter

Ready to brave the cold? Check out this information for planning a winter visit.

Snowmobiles and a snowcoach ride by a small group of bison
Ride a Snowmobile or Snowcoach

Take a guided tour of wintry Yellowstone.

Snowmobile rider taking photo
Snowmobile Access Program

Learn about our non-commercially guided snowmobile program.

A fox jumps in the air with its nose pointed down towards the ground, which is blanketed in snow.
Winter Ecology

Winter in Yellowstone is a place of magic and vulnerability. Learn how wildlife endures the extremes of cold and the absence of food.

two park rangers walking with bison seen in the background

Learn about the current natural and cultural resource issues that Yellowstone is managing for this and future generations.


Winter Use Management News

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    Last updated: March 7, 2024

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