| Abbreviation | Definition |
|---|---|
| SJVR | San Joaquin Valley Railroad Company |
| SKAU | Skaff Cryogenics |
| SKCX | ARCO Chemical |
| SKCX | ARCO Chemical Company |
| SKGX | Sibley Railcar and Parts |
| SKIU | XTRA Intermodal |
| SKIZ | XTRA Intermodal |
| SKNX | Saskatchewan Grain Car Corporation |
| SKOL | South Kansas and Oklahoma Railroad |
| SKPR | Southern Kent and Pacific RailRoad Company |
| SKPR | Southern Kent and Pacific RR |
| SKPX | Saskatchewan Grain Car Corporation |
| SKRX | Schuylkill Railcar |
| SKRX | Schuylkill Railcar L. P. |
| SKRZ | XTRA Intermodal |
| SKTX | Ski Train |
| SKYU | CAI International |
| SL | Salt Lake City Southern Railroad |
| SL | Short Line |
| SL | Steam Locomotive |