| Abbreviation | Definition |
|---|---|
| URDX | United States Steel |
| URN | Union Railways North |
| URR | Underground Railroad Radio |
| URR | Union Railroad Company ( Pittsburgh, Pennsylvania) |
| URR | Union Railroad Pittsburgh |
| URRA | Upper Rail Retracted Auxiliary |
| URTX | Union Refrigerator Transit Lines (GATX) |
| URY | Union Railway of Memphis |
| USAU | Pan Texas Leasing |
| USAU | Pan Texas Leasing Incorporated |
| USAX | United States Army |
| USAX | United States Department of Defense - Troop Support and Aviation Material Readiness Command (Intraplant) |
| USAZ | XTRA Intermodal |
| USBX | General Electric Railcar Services Corporation |
| USBX | US Borax & Chemical (CIT Group) |
| USCU | Union Steam Ship Company of NZ Limited |
| USCU | Union Steam Ship of NZ |
| USCX | William G. Simon |
| USCX | William G. Simon Company Railroad |
| USEX | Evans Railcar Leasing (GE Rail Services) |