CN/NAR was the only railroad that had GMD1 locomotives although some have now been dispersed to shortlines. GMD1s are in four families:
11xx — These originally had A-1-A trucks which were replaced with B-B trucks from retired GP9s. For the most part they have spark arrestors and were painted in the "noodle and red cab" (NR) paint scheme.
14xx — These also have B-B trucks inherited from GP9s. They are painted in the "zebra stripes and black cab" (ZB) paint scheme and do not have spark arrestors.
16xx — This series has retained the original A-1-A trucks. They are painted in the "zebra stripes and black cab" (ZB) paint scheme and do not have spark arrestors. (all retired or rebuilt)
19xx — These have GP9 B-B trucks and originally had steam generators which have now been removed. (all retired)