In Monongahela Ry. Co. v. Black, 235 F.2d 406 (4th Cir. 1956), the plaintiff, an employee of the defendant railroad, was hit by a moving freight car on the side track at the Arkwright coal mine. The coal company did not own any rolling stock or engines. It was not equipped to inspect or repair freight cars. It was a customer whose sole connection with the railroad was loading its cars. The railroad had claimed that it was not liable under the act because its car was not "in use on its line." The court reasoned that the placing of cars on the side track for loading was part of the interstate movement of coal over the railroad's system and that the side track on the property of this private corporation existed "solely for the purpose of promoting commerce" on the railroad's line and was utterly valueless without the railroad. Monongahela, 235 F.2d at 407. The court held that since the car in question was being used as a part of the railroad's business in interstate commerce, the Safety Appliance Act applied. Monongahela, 235 F.2d at 407.