| Abbreviation | Definition |
|---|---|
| PLW | P L and W Railroad Incorporated |
| PLW | Pittsburgh, Lisbon & Western Railroad (PL&W Railroad) |
| PLWX | General Electric Railcar Services Corporation |
| PLWX | Pullman Leasing Co. (GE Capital Railcar Services) |
| PM | Pere Marquette |
| PM | Pere Marquette Railway (CSX Transportation) |
| PMAX | PMA Transportation Corporation |
| PMGX | Pacific Metal Limited |
| PMIX | Pittman Moore |
| PMIX | Pittman Moore Incorporated |
| PMLX | Prairie Malt |
| PMLX | Prairie Malt Limited |
| PMOX | Phillip Morris |
| PMOX | Phillip Morris Incorporated |
| PMR | Proto Matrix Rail |
| PMRT | Pere Marquette Rail-Trail |
| PN | Pennsylvania Northeastern Railroad |
| PN | Piedmont and Northern Railway (CSX Transportation) |
| PNCU | Pacific Environmental |
| PNEU | Pacific Northwest Equipment |