The Dotsero Southern ordered 14 GP40 locomotives in July 1970, one year prior to the railroad opening. These units were delivered between December 1970 and February 1971.
All locomotives were ordered in base spec other than the fitting of dynamic brakes. Over the years, the railroad took to experimenting with different headlight placements to increase visibility. Most units ended up being retrofitted with a roof mounted horizontal headlight and nose mounted vertical gyralight. A few units didn't receive these changes, rather keeping the base light spec, those being #1977, #1979, and #1982. Units fitted with gyralights were given the ability to steer the light in order to see around corners. This was achieved by allowing separate control to each motor in the light, giving the driver independent to both vertical and horizontal tilt. Nearly every GP40 was fitted with a Nathan M3 except for #1970, which used an M5.
The choice to buy stock locomotives came with downsides, notably the lack of plows being fitted. In 1972, just after a rockslide in Glenwood Canyon, rocks would derail and damage engine #1981. While this derailment wouldn't have been prevented with the addition of plows, the damange to the front pilot would've been greatly reduced. After 1972, all mainline units would be required to have front plows fitted.
After years of use, these engines were beginning to show their age. Rather than rebuilding the fleet, the decision was made to trade the GP40s in for credit toward GP60 replacements. The last run of a GP40 on the DSRR system was in September of 1985. Two GP40s have been kept in storage, those being #1970 and #1971.
| Unit Number | Build Date | Last Run | Notes |
|---|---|---|---|
| DSRR 1970 | December 1970 | September 17th, 1985 | Put into storage. |
| DSRR 1971 | December 1970 | September 17th, 1985 | Put into storage. |
| DSRR 1972 | December 1970 | September 17th, 1985 | Traded in to EMD. |
| DSRR 1973 | December 1970 | September 17th, 1985 | Traded in to EMD. |
| DSRR 1974 | December 1970 | September 17th, 1985 | Traded in to EMD. |
| DSRR 1975 | January 1971 | September 17th, 1985 | Traded in to EMD. |
| DSRR 1976 | January 1971 | November 12th, 1979 | Wreaked in Minturn, 1979. |
| DSRR 1977 | January 1971 | September 17th, 1985 | Traded in to EMD. |
| DSRR 1978 | January 1971 | September 17th, 1985 | Traded in to EMD. |
| DSRR 1979 | January 1971 | September 17th, 1985 | Traded in to EMD. |
| DSRR 1980 | February 1971 | December 25th, 1975 | Used as parts locomotive after a unit fire. Scrapped. |
| DSRR 1981 | February 1971 | September 17th, 1985 | Traded in to EMD. |
| DSRR 1982 | February 1971 | September 17th, 1985 | Traded in to EMD. |
| DSRR 1983 | February 1971 | September 17th, 1985 | Traded in to EMD. |