| Abbreviation | Definition |
|---|---|
| AZCR | Arizona Central Railroad Incorporated |
| AZCX | Azcon Corporation |
| AZER | Arizona Eastern Railway |
| AZEX | Arizona Electric Power Cooperative |
| AZEX | Arizona Electric Power Cooperative Incorporated |
| AZMX | Arizona Railway Museum |
| AZS | Arizona Southern Railroad |
| AZXX | Arizona Chemical |
| B&M | Boston and Maine |
| B&ME | Boston Maine |
| B&ME | Boston & Maine |
| B&O | Baltimore Ohio |
| B&O | Baltimore & Ohio |
| B&O | Baltimore and Ohio Railroad |
| BA | Boston and Albany Railroad (Conrail) |
| BA | Consolidated Rail Corporation |
| BADX | Baden Investment |
| BADX | Baden Investment Company |
| BAEU | Bae Systems |
| BAEX | Baer & Erickson (The Andersons) |