| Abbreviation | Definition |
|---|---|
| RALX | Radnor Rail Limited |
| RAMX | Rail America (Genessee & Wyoming) |
| RAPX | Rapco Transportation |
| RAPX | Rapco Transportation Company |
| RARW | Rarus Railway |
| RARW | Rarus Railway Company |
| RAS | Rail Adapter System |
| RASR | Routed Aluminum Side Rail |
| RASX | C.A. Rasmussen |
| RATU | Royal Atlantic |
| RATX | RailTex Service |
| RAWX | Platte River Power Authority |
| RAX | RPI- AAR Cooperative Test Program |
| RAX | RPI-AAR Cooperative Test Program |
| RBBN | Chicago, Burlington and Quincy Railroad (BNSF Railway) |
| RBBQ | Chicago, Burlington and Quincy Railroad (BNSF Railway) |
| RBBX | Ringling Bros. and Barnum and Bailey |
| RBBX | Ringling Brothers and Barnum and Bailey Circus |
| RBCS | Rail-Bridge Corporation (BNSF Railway) |
| RBCU | Railbridge Corporation |