| Abbreviation | Definition |
|---|---|
| SPDZ | Southern Pacific Railroad (Union Pacific Railroad) |
| SPDZ | Union Pacific Railroad Company |
| SPEG | Spencerville and Elgin Railroad |
| SPFE | Pacific Fruit Express (Union Pacific Railroad) |
| SPFE | Union Pacific Railroad Company |
| SPFZ | Southern Pacific Railroad (Union Pacific Railroad) |
| SPFZ | Union Pacific Railroad Company |
| SPGX | Suburban Propane |
| SPGX | Suburban Propane LP |
| SPIX | Sweeteners Plus |
| SPLR | Stansted Park Light Railway |
| SPLU | Compania Trasatlantica Espanola |
| SPLU | Compania Trasatlantica Espanola ( Spanish Line) |
| SPLZ | Southern Pacific Railroad (Union Pacific Railroad) |
| SPLZ | Union Pacific Railroad Company |
| SPMW | Southern Pacific Maintenance-of-Way |
| SPMW | Southern Pacific Railroad (Union Pacific Railroad) |
| SPPU | Splosna Plovba Piran |
| SPQ | Southern Pacific Railroad (Union Pacific Railroad) |
| SPQ | Union Pacific Railroad Company |