| Abbreviation | Definition |
|---|---|
| DMRC | Delhi Metro Rail Corporation |
| DMU | Des Moines Union Railway |
| DMU | Diesel Multiple Unit |
| DMVW | Dakota Missouri Valley and Western Railroad Incorporated |
| DMVW | Dakota, Missouri Valley and Western Railroad |
| DNAX | Dana Railcare |
| DNCX | Denco Petroleum Incorporated |
| DNE | Duluth and Northeastern Railroad |
| DNE | Duluth and Northeastern Railroad Company |
| DNRA | Danish National Railways Authority |
| DO | Dispatcher's Office |
| DOCU | USDOC NOAA / PMEL |
| DOCX | Du Pont Canada |
| DOCX | Du Pont Canada Incorporated |
| DODU | U.S. Department of Defense |
| DODU | United States Department of Defense |
| DODX | U.S. Department of Defense - Military Traffic Management Command |
| DODX | United States Department of Defense |
| DODZ | U.S. Department of Defense |
| DODZ | United States Department of Defense |