| Abbreviation | Definition |
|---|---|
| ARCX | Alaska Rail Car (Arizona Rail Car) |
| ARCX | Arizona Rail Car Incorporated |
| ARDP | Australian Railway Detail Photo |
| ARDP | Missouri Pacific Railroad (Union Pacific Railroad) |
| ARDP | Union Pacific Railroad Company |
| ARDU | CARU Containers |
| ARDU | CATU Containers S. A. |
| ARE | A&R Line |
| ARE | A. and R. Line Incorporated |
| AREMA | American Railway Engineering and Maintenance-of-Way Association |
| AREX | Aeropres Corporation |
| AREX | Airport Express |
| ARGX | Associated Railcar |
| ARGX | Associated Railcar Incorporated |
| ARHS | Anthracite Railroads Historical Society |
| ARHU | CARU Containers |
| ARHU | CATU Containers S. A. |
| ARHX | Arch Mineral Corporation |
| ARIX | Arco Industrial Gases (GE Rail Services Corporation) |
| ARIX | BOC Gases |