be controlled from the plow. In areas of particularly deep snowfall, such as California's Donner Pass, railroads sometimes created a train consisting of a rotary snowplow at each end, with the blade ends pointing away from each other, and two or three locomotives coupled between them. With a plow on each end, the train was able to return to its starting location even if the snow covered the tracks it had just passed over. Such a train would also be able to clear multiple track mainlines efficiently as it could make a pass in one direction on one track, then reverse direction and clear the next track. This practice became standard for the Southern Pacific Railroad on Donner Pass following the January 1952 stranding of the City of San Francisco train; during attempts to clear the avalanches that had trapped the train, two rotary plows were trapped by subsequent avalanches, and the crew of a third was killed when their plow was hit by an avalanche. Rotary snowplows are expensive because of their high maintenance costs, which the railroad incurs regardless of whether they are needed in a given year. As a result, most railroads have eliminated their rotaries, preferring to use a variety of types of fixed-blade plows that have significantly lower maintenance costs, in conjunction with bulldozers, which can be used year-round on maintenance-of-way projects. In addition, because rotaries leave an open-cut in the snowbank that fixed-blade plows cannot push snow past, once rotaries have been used, they must be used for all further significant snowfalls until the snowpack has melted. Since rotaries, which need some form of fuel to power the blades, also cost more to operate than fixed-blade plows, they are now generally considered to be a tool of last resort for the railroads that own them. The few remaining rotary plows in North America are either owned by museum railroads or are kept in reserve for areas with poor road access and routine severe snowfall conditions. The largest remaining fleet of rotaries consists of Union Pacific Railroad's six plows reserved for Donner Pass. Japan sees widespread use of rotary snowplows in its many mountain passes. Power Early rotaries had steam engines inside their car bodies to power the blades; a few are still in working order, and in particular one on the White Pass and Yukon Route in Alaska performs annual demonstration runs through thick