The Union Pacific operations building reminds workers of the importance of safety, especially given the activity in the busy North Yard in Denver, Colorado.

UP heavies outnumber the light power in the Union Pacific's North Yard in Denver, Colorado.

UP 688 (GP38-2) joins three other light motors in the North Yard in downtown Denver, Colorado.

UP 688 (GP38-2) waits for the call to action to head into the North Yard in downtown Denver, Colorado to sort freight cars.

UP 688 (GP38-2) works a cut of cars deep in the North Yard in Denver, Colorado.

UP 688 (GP38-2) runs long hood forward in a Siamese configuration as it works shuffling cars in the North Yard in Denver, Colorado.

UP 688 (GP38-2) repositions in the North Yard to assemble a train.

UP 688 (GP38-2) runs into the Union Pacific's North Yard in Denver, Colorado to sort freight cars.

UP 688 (GP38-2) works a yard in Commerce City, Colorado, waiting for the signal to grab a cut of gondolas from a nearby scrap metal business.

Light power waits for orders in the Union Pacific's North Yard in Denver, Colorado.

UP 688 (GP38N) moves into the North Yard in Denver, Colorado to sort rolling stock.

UP 688 (GP38N) runs in the Union Pacific's North Yard in Denver, Colorado.

A wide shot at the Union Pacific's North Yard in Denver catches two trains that have just entered the yard, while UP 688 (GP 38-2) begins to sort a cut from a train that arrived the day before.

UP 688 (GP38-2) pulls a cut of cars out of the Union Pacific's North Yard, which will then get sorted onto various tracks.

UP 688 (GP38-2) strains to pull a cut of cars out of the North Yard for sorting.