With its snow-covered mountains and a variety of wildlife, Yellow Stone National Park is one of the scenic treasures of the United States. Located primarily in Wyoming, the park hosts millions of visitors every year. If you plan to travel within the park, keep in mind advice from the National Park Service.
Seasonal Travel
Travel varies vastly from season to season. Roads are generally open in the summer except for cases of rock or mud slides, wild fires, accidents or road construction. Early snows in the fall can cause some roads to close temporarily. In the winter almost all roads are closed to motor vehicles, but snowmobiles and other snow vehicles with tracks are allowed. Roads begin to open for the spring by the latter part of April but can close if snowfall continues.
Driving Time
Grand Loop is the main road through Yellowstone National Park; it passes by most of the major attractions. These include Old Faithful, Yellowstone Lake and the Grand Canyon of Yellowstone. The maximum speed limit on the Grand Loop is 45 miles per hour, but the speed limit drops during some of the winding and twisting sections of this narrow road. Allow yourself at least two days to fully travel the loop due to the size of the park and being sometimes stuck in heavy traffic.
Safety Awareness
Buffalo(水牛)often block the roads in the park as
they move through the fields. If a group is traveling across the road you are
on 
you can either wait for them to pass or find an alternative route. If you get out of your vehicle, the National Park Service says to stay at least 25 yards from any buffalo (and 100 yards or more away from bears and wolves). Buffalo are particularly unpredictable and charge people at speeds up to 30 mph.
You can take your bicycle on any public roads and routes designed for bikes, but bicycles are not allowed on the park roads which are narrow with few shoulders. Altitudes range from 5, 300 to 8, 860 feet. The National Park Service recommends cyclists wear helmets and noticeable clothing.
