Rotary snowplows are specialized train cars with a large front-mounted rotating wheel of blades (up to 12 feet / ~3.7 m in diameter) that cut through deep or packed snow and throw it aside. They were developed in the late 19th century because traditional wedge plows often couldn't handle heavy mountain snow. One early version traces its concept to a Canadian dentist, J.W. Elliot, in 1869. These plows are pushed by locomotives and can clear track far more effectively than earlier designs. But nothing compares to the plowing that ARA undergoes during maintenance.