UP 1507 (GP40M) passes the Union Pacific's operations building at the North Yard in Denver, Colorado.

UP 1507 (GP40M) heads to the BNSF yard in Denver, Colorado with a cut of freight cards from the Union Pacific's North Yard.

UP 1507 (GP40M) brings a freight into the BNSF yard in downtown Denver, Colorado.

UP 1502 (GP40M) works the North Yard in Denver Colorado.

UP 1507 (GP40M) leads a freight towards the BNSF yard in Denver, Colorado.

UP 1507 (GP40M) is entering the BNSF's Denver Yard with a cut of freight cars and will head back to the UP North Yard after dropping off the cars.

UP 1507 (GP40M) moves a cut of cars early in the morning in the Union Pacific's North Yard in Denver, Colorado.

A wide-angle view of the Union Pacific's North Yard in Denver, Colorado shows the fuel and sand service islands on the left, the ready tracks in the middle (with a former Southern Pacific GP40M - ... (more)

UP 1507 (GP40M) sorts cars in the North Yard in Denver, Colorado.

UP 1507 (GP40M) sits waiting in the Union Pacific's North Yard for its turn to sort cars.

Snow and subfreezing temperatures blanket the Union Pacific's North Yard in Denver, Colorado.

In need of a facelift, BNSF 3022 with 9 loads of lumber are tied down for the night.

The majority of power in the Denver North Yard on this day is light units, including UP 1507 (GP40M).

In another month the snow will be flying and more scenes of UP power working the North Yard in snow will be seen.

BNSF 3020 (GP40M) is one of the many former BN units that can be found working the Denver Yard.