| Abbreviation | Definition |
|---|---|
| NJ | Niagara Junction Railway (Canadian Pacific Railway) |
| NJCL | North Jersey Coast Line |
| NJCX | New Jersey Rail Carrier |
| NJDX | GE Rail Services |
| NJII | New Jersey, Indiana and Illinois Railroad (Norfolk and Western Railway) |
| NJRC | New Jersey Rail Carrier |
| NJT | New Jersey Transit |
| NJT | Newton Junction Terminal |
| NJTR | New Jersey Transit |
| NJTR | NJ Transit Rail Operations |
| NKCR | Nebraska Kansas and Colorado RailNet Incorporated |
| NKCR | Nebraska, Kansas and Colorado Railnet |
| NKP | New York, Chicago and St. Louis Railroad (Norfolk Southern) |
| NKP | Nickel Plate Railroad |
| NKP | Norfolk Southern Railway Company |
| NLAX | National Aeronautics and Space Administration |
| NLAX | National Aeronautics and Space Administration (NASA) |
| NLCL | Northern Lands Railway (Neyveli Lignite Corporation Limited) |
| NLG | Kansas City Southern Railway Company |
| NLG | North Louisiana and Gulf Railroad (Kansas City Southern Railway) |