YELLOWSTONE NATIONAL PARK, Wyo. -- Two bulldozers have broken down in Yellowstone National Park since crews began clearing park roads of the heavy snowpack that accumulated during the winter.

The park has rented two machines as replacements in an attempt to clear roads from Mammoth to the West Entrance, and south to Old Faithful.

Weather and equipment permitting, the roads will begin opening again to vehicles on Friday, April 18, from Mammoth to Old Faithful; Madison to the West Entrance and Norris to Canyon. The roads from Canyon to Lake and from Lake to the East Entrance are scheduled to open on Friday, May 2; Lake to the South Entrance and West Thumb to Old Faithful, Tower to Tower Fall on Friday, May 9; and Tower Fall to Canyon over Dunraven Pass on Friday, May 23.

Yellowstone spokesman Al Nash said the park this winter may have had the most snowfall it has seen in seven to 10 years.

Nash said that, during the month of March alone, the park's South Entrance received 101 inches. He said the snow is so deep in some places that the bulldozers have to push it off the roadway in layers, to feed it to rotary plows that then blow it off the road surface.