| Abbreviation | Definition |
|---|---|
| IMNU | Seateq Corporation |
| IMPQ | Imperial Sugar |
| IMQ | ISP Minerals |
| IMRL | Illinois and Missouri Rail Link (Iowa, Chicago and Eastern Railroad) |
| IMRL | Iowa, Chicago, and Eastern Railroad Corporation (formerly Illinois and Missouri Rail Link, L.L.C.) |
| IMRR | Illinois and Midland Railroad |
| IMRR | Illinois and Midland Railroad, Inc. |
| IMRZ | Iowa Interstate Railroad Limited |
| IMSX | IMCO Services (International Mill Service) |
| IMSZ | Intermodal Systems |
| IMSZ | Intermodal Systems Incorporated |
| IMTX | Ag Processing Incorporated |
| IMTX | Multifoods Transportation (AG Processing) |
| IMXZ | Intermodal Express |
| IMXZ | Intermodal Express Incorporated |
| IMZ | IVEL Mine |
| IN | Indiana Northeastern Railroad |
| IN | Indiana Northeastern Railroad Company |
| INAZ | Intalco Aluminum |
| INBU | Seacube Container Leasing |