UP 1817 (SD40N) sits in the Union Pacific's North Yard in Denver, Colorado.

UP 1826 (SD40N) pulls up to the yard crew who will board as head to the north end of the yard.

I think Alfred Hitchcock would have liked this photo. UP 1826 (SD40N) works the Union Pacific's North Yard in Denver, Colorado as hundreds of birds circle, waiting for the chance to land on the tr... (more)

RTD 4037 (Hyundai Eagle P3) commuter rail train arrives from Denver International Airport as it drops down from the elevated track north of Denver's Union Station.

It's the blue hour in Denver, Colorado as UP 6999 (AC4400CW) leads an oil can train towards the 36th Street Yard.

A visiting BNSF motors sits among the Union Pacific motors in the UP's 36th Street Yard in Denver, Colorado.

The California Zephyr runs through the BNSF's Denver Yard as it heads towards the Union Station terminal in downtown Denver.

The Amtrak Winter Park Express Ski Train passes by the Union Pacific's North Yard in Denver, Colorado as a Colorado sunrise provides a colorful sky.

The California Zephyr winds its way through the BNSF's Denver Yard as it heads towards Denver's Union Station.

UP 845 (GP38-2) works the Union Pacific's North Yard in Denver, Colorado.

Denver Rock Island Railroad's GP9 sits with other motors in the yard in Denver, Colorado.

BNSF 6751 (ES44C4) joins other heavies in the yard of the engine servicing facility in Denver, Colorado as a RTD commuter train drops down from the elevated track.

BNSF 9709 (Executive Grinstein SD70MAC) brings the Coors Beer Train into the Denver.

BNSF 2719 (ex-Burlington Northern GP39-2) and BNSF 1732 (ex-ATSF SD40-2) sit at the engine servicing facility in downtown Denver, Colorado.

BNSF 1733 (SD40-2) pulls a cut of cars out of the Denver Yard for sorting.