Bicyclists willing to brave the unpredictable elements of spring in Yellowstone can ride 49 miles of park roads from the West Entrance to Mammoth Hot Springs for a small period of time each spring when the roads have been plowed but aren't yet open to motorized vehicles. As conditions allow, bicycles will also be permitted from the East Entrance to the east end of Sylvan Pass, and the South Entrance to West Thumb. Check the Spring and Fall Bicycling page for road segment status. Yellowstone National Park Bike Trail West Yellowstone West Entrance Madison River Riverside. Several gravel roads are open to both bicycle and automotive traffic. The Old Gardiner Road allows two-way bike traffic and one-way auto traffic. This road is best suited for mountain bikes. Please do not block gates when parking. Yellowstone National Park Bike Trail gardiner North Entrance Mammoth Hot Springs Mammoth Hot Springs Area.