| Abbreviation | Definition |
|---|---|
| GRCX | Granite Rock Company |
| GRD | Guard Rail Detection |
| GRDX | Grand River Dam Authority |
| GREX | Georgetown Rail Equipment |
| GREX | Georgetown Rail Equipment Company |
| GRFF | Georgia and Florida Railroad |
| GRFF | Georgia and Florida Railroad Company |
| GRIV | Gauley River Railroad |
| GRIV | Gauley River Railroad LLC |
| GRL | Gross Rail Load |
| GRLW | Greenville & Western Railway (Western Carolina Railway Service Corporation) |
| GRMX | Gopher State Railway Museum |
| GRN | Greenville and Northern Railway |
| GRNR | Grand River Railway |
| GRNR | Grand River Railway Company |
| GRNW | Great Northwest Railroad |
| GROI | Genesee Rail-One |
| GROX | First Union Rail |
| GROX | Growth Nonstop Cooperative (First Union Rail) |
| GRPX | General Chemical (CIT Financial) |