| Abbreviation | Definition |
|---|---|
| PAPX | Pennsylvania Pullmans Incorporated |
| PARX | Pan American Railway |
| PARX | Pan American Railway Company |
| PARY | Prairie Trunk Railway |
| PAS | Pan Am Southern |
| PASX | Pacer Stacktrain |
| PATH | Port Authority Trans-Hudson |
| PATZ | Pacer Stacktrain |
| PAUT | Pennsylvania and Atlantic Railroad (Conrail) |
| PBFX | IBP (Tyson Foods) |
| PBFX | IBP Incorporated |
| PBIU | Pro Box |
| PBL | Philadelphia Belt Line Railroad |
| PBL | Philadelphia Belt Line Railroad Company |
| PBLU | Containers and Pressure Vessels Limited |
| PBLX | MHC Incorporated - Subsidiary of Conagra Incorporated |
| PBLX | Pillsbury |
| PBMZ | Pattison Brothers Mississippi River |
| PBNE | Philadelphia Bethlehem and New England Railroad Company |
| PBNE | Philadelphia, Bethlehem and New England Railroad (Lehigh Valley) |