| Abbreviation | Definition |
|---|---|
| OWLU | Ocean World Lines |
| OWLU | Ocean World Lines Incorporated |
| OWNR | Oregon - Washington, Navigation and Railway Company |
| OWSX | Oil Well Supply |
| OWTX | Oneida & Western Transportation |
| OWTX | Shamrock Coal |
| OXYU | Eurotainer U.S. Incorporated |
| OXYU | Eurotainer US |
| PACU | Pacer International |
| PACX | Plasser American Corporation |
| PACY | Prairie Central Railway |
| PAE | Consolidated Rail Corporation |
| PAE | Peoria and Eastern Railway (Conrail) |
| PAIX | Pol-Tex Internation Division of Poly-America |
| PAIX | Poly- America, Inc. |
| PAL | Paducah and Louisville Railroad |
| PAL | Paducah and Louisville Railway |
| PAM | Pittsburgh Allegheny and McKees Rocks Railroad Company |
| PAM | Pittsburgh, Allegheny and McKees Rocks Railroad |
| PAPX | Pennsylvania Pullmans |