UP 1358 (GP40N) joins other light power at the North Yard in Denver, Colorado.

UP 5910 (AC4400CW-CTE) gets ready to lead an oil can train west on the Moffat Tunnel Sub into the Colorado Rocky Mountains.

UP 1507 (GP40N) works the North Yard in Denver, Colorado.

UPY 618 (GP15-1) works on shuffling a string of hoppers into the ladders in the North Yard in Denver, Colorado.

UP 2238 (GP38-2) waits in the Union Pacific's North Yard in Denver, Colorado for orders to hit the yard.

UP 1837 (SD40-2) moves a flat car and an oil can deeper into the North Yard in Denver, Colorado.

Fog moves through a sunny UP North Yard in Denver, Colorado.

A BNSF Geep lashes up to a heavy in the engine servicing yard in downtown Denver, Colorado.

A pair of former Burlington Northern Cascade Green units work a string of cars in the large yard in Denver, Colorado.

BNSF 1746 (SD40-2) heads into the BNSF yard in Denver, Colorado to shuffle cars.

BNSF 7213 (ES44DC) leads a stack towards the Denver Yard as it begins the journey east on the Brush Sub.

BNSF 7213 (ES44DC) leads a stack train under the Park Avenue Viaduct in Denver, Colorado.

UP 1837 (SD40-2) shuffles cars in the North Yard in Denver, Colorado.

UP 1837 (SD40-2) works the North Yard in Denver, Colorado.

UP 5910 (AC4400CW-CTE) waits for a signal before heading west on the Moffat Tunnel Sub into the Colorado Rocky Mountains.