| Abbreviation | Definition |
|---|---|
| SWTZ | St. Louis Southwestern Railway |
| SWTZ | St. Louis Southwestern Railway Company |
| SWYX | OCI Chemical Wyoming Company |
| SWYX | Stauffer Chemical of Wyoming |
| SXSX | Ron Johnson and Associates |
| SYRR | Sandusky River Railroad |
| SYRX | ADM Transportation |
| SYRX | Minnesota Corn Processors Incorporated |
| SYSX | United States Systems Incorporated |
| SYSX | Winter Bird Corporation |
| SZLU | Seacube Container Leasing |
| SZMC | ShenZhen Metro Company |
| TAA | Train Alteration Advice |
| TACX | American Coal Sales Company |
| TACX | Transport Arts Corporation |
| TAEA | Tangipahoa and Eastern |
| TAEX | The Andersons |
| TAG | Norfolk Southern Railway Company |
| TAG | Tennessee, Alabama and Georgia Railway (Norfolk Southern Railway) |
| TAGX | Texoma AG Products |