| Abbreviation | Definition |
|---|---|
| ARRG | Altra Railroad |
| ARRX | Anthracite Railroads Historical Society |
| ARS | Arkansas Southern Railroad |
| ARSX | Aristech Chemical Corporation |
| ARSX | Aristech Chemical Corporation (Sunoco) |
| ART | A&R Terminal Railroad |
| ART | American Refrigerator Transit |
| ART | American Refrigerator Transit Company |
| ART | The National Rail code for Arrochar and Tarbet railway station, United Kingdom |
| ARTC | Australian Rail Track Corporation |
| ARTU | CARU Containers |
| ARTU | CATU Containers S. A. |
| ARW | Arkansas Western Railway |
| ARW | Arkansas Western Railway Company |
| ARWX | Alabama River Woodlands |
| ARWX | Alabama River Woodlands Incorporated |
| ARZC | Arizona and California Railroad |
| ARZC | Arizona and California Railroad Company |
| AS | Abilene and Southern Railway (Missouri Pacific Railroad) |
| ASAB | Atlanta and St. Andrews Bay Railway (Bay Line Railroad) |