The snow has been so sparse from West Yellowstone, Montana into the park that the National Parks Service decided to plow the road and open it to limited public transportation Thursday.

That means snowmobilers, who usually enter the park from West Yellowstone, are out of luck for the remainder of the winter season. Patches of bare pavement made snowmobiling tricky and threatened to damage snow-grooming equipment, according to the National Park Service.

Traffic will be restricted to vans, buses and rubber-tracked snowcoaches operated by Park Service-authorized winter. All drivers must be out of the park by 6 p.m. each day unless other arrangements are made. After March 12 the road will be opened to private vehicles. That's the official end of the winter season at Yellowstone National Park.

It's one of the earliest endings for snowmobile traffic in recent park history.