| Abbreviation | Definition |
|---|---|
| NPB | Norfolk and Portsmouth Belt Line Railroad Company |
| NPCU | Newport Tank Containers |
| NPCX | Equistar Chemicals LP |
| NPCX | Northern Petrochemical (Equistar Chemicals) |
| NPF | Northern Pacific Railway |
| NPIX | Chem-Nuclear Systems |
| NPIX | Chem-Nuclear Systems L.L.C. |
| NPJR | Northern Pacific Junction Railway |
| NPPX | Nebraska Public Power District |
| NPR | Northern Plains Railroad |
| NPR | Northern Plains Railroad Incorporated |
| NPRT | Nanjing Puzhen Rail Transport |
| NPRU | Sea Star Line |
| NPRX | Yakima Interurban Lines Association |
| NPSU | Nigel Parks |
| NPSU | Nigel Parks Limited |
| NPT | Portland Terminal Railroad |
| NPT | Portland Terminal RailRoad Company |
| NPT | Portland Terminal RailRoad Company ( Oregon) |
| NPTU | Neptune Leasing |