| Abbreviation | Definition |
|---|---|
| RCWZ | Union Pacific Railroad |
| RCWZ | Union Pacific Railroad Company |
| RDC | Rail Diesel Car |
| RDCX | Regional Disposal |
| RDCX | Regional Disposal Company |
| RDG | Consolidated Rail Corporation |
| RDG | Rail Delivery Group |
| RDG | Reading Railroad (Norfolk Southern) |
| RDIX | Rapid Industrial Plastics |
| RDIX | Rapid Industrial Plastics Company |
| RDMC | Railway Diagnostic and Monitoring Conference |
| RDMZ | TAL International |
| RDMZ | Transamerica Leasing Incorporated |
| RDRU | Roeder Cartage Co |
| RDSZ | CSX Transportation Incorporated |
| RDSZ | R.R. Donnelly & Sons (CSX Transportation) |
| RDWZ | Roadway Express |
| RDWZ | Roadway Express Incorporated |
| RE | Relco |
| REA | Railroad Enthusiast Association |