| Abbreviation | Definition |
|---|---|
| SSOR | Sisseton Southern Railway |
| SSOR | Sisseton Southern Railway Company |
| SSPB | Seaspan International Limited |
| SSPX | A. E. Staley Manufacturing Company |
| SSPX | AE Staley Manufacturing |
| SSR | Solid Side Rail |
| SSR | Southern Shorthaul Railroad |
| SSRA | Shadow Strategic Rail Authority |
| SSRS | Scottish Strategic Rail Study |
| SSSU | Hansen and Tidemann |
| SSSU | Hansen and Tidemann Incorporated |
| SSSX | Transportation Logistics Corporation |
| SSSZ | Hansen and Tidemann |
| SSSZ | Hansen and TidemannIncorporated |
| SSVX | S S I Industries |
| SSVX | SSI Industries |
| SSW | St. Louis Southwestern Railway (Union Pacific Railroad) |
| SSW | Union Pacific Railroad Company, St. Louis SouthWestern Railway segment |
| SSWN | St. Louis Southwestern Railway (Union Pacific Railroad) |
| SSWN | Union Pacific Railroad Company |