The term "2-8-4" refers to a type of steam locomotive wheel arrangement. In this configuration, the locomotive has two leading wheels, eight driving wheels, and four trailing wheels. This design allows for better stability and power, making it suitable for hauling heavy freight and passenger trains over long distances. The 2-8-4 wheel arrangement was popularized in the early 20th century, particularly in the United States. It is often associated with the Berkshire type locomotives, which were known for their efficiency and ability to handle steep grades. This design contributed significantly to the development of rail transport during that era.