Side Dump care are a very versatile class of railroad car, designed to deposit their load to either side of the tracks, rather than between the rails like a ballast hopper. This feature is utilized by the railroads in maintenance-of-way roles for rapidly building up fills and cuts with stone, rip-rap or soil as well as for depositing ballast. Side dump cars are also used in revenue service hauling ore, limestone, gravel, and coal, in industrial settings hauling waste or recycling materials, and in mining operations. Their low sides enable easy loading of material, and their rapid discharge rates - some less than 10 seconds - and ability to take a lot of abuse have earned them the nickname of a "dump truck on rails".
The Atlas DIFCO (Differential Steer Car Company) side dump car is modeled after the air-activated, all-welded construction, 50 cubic yard car which has been a familiar fixture on the rails both in the US and abroad from the late 1960s through today, and features prototypically accurate scale dimensions, roller bearing trucks, and knuckle couplers.