A Union Pacifc oil can train passes a BNSF freight at Rocky, Colorado on the Moffat Tunnel Sub.

UP 7801 (ES44AC) leads a train through Little Ten Curve at Rocky, Colorado.

The California Zephyr 5 train has left Denver and is running towards Rocky, Colorado on the Moffat Tunnel Sub.

Dynamic weather moves in over the mountains at Plainview, Colorado as UP 5624 (AC4400CW-CTE) leads a freight through Rocky on the Moffat Tunnel Sub.

An eastbound BNSF freight is in the clear in the siding at Rocky, Colorado, on January 19, 2002, and a man is on the ground to inspect Union Pacific’s MDVRO working west on the main line.

UP 7104 (AC4400CW) leads an oil can train through Big Ten Curve as it heads down the Moffat Tunnel Sub towards Denver, Colorado.

In a dispatching move that didn't quite make sense, the California Zephyr 5 train meets the California Zephyr 6 train, but since a UP oil train occupied the siding at Rocky, Colorado, the 5 train ... (more)

The cows are more interested in the photographer as the California Zephyr, led by Amtrak engine #82 in Phase VII paint, heads up Big Ten Curve at Rocky, Colorado.

UP 1943 (SD70ACe) Runs under Highway 93 as it heads to Rocky, Colorado.

UP 5567 (AC4400CW-CTE) muscles a freight through Little Ten Curve at Rocky, Colorado.

An optical illusion makes it appear as though the Union Pacific oil train is running up an extra steep grade at Rocky, Colorado.

BNSF 9214 (SD70ACe) muscles the Denver to Provo train through Rocky, Colorado on the Moffat Tunnel Sub.

A Union Pacific loaded coal train is running through Arena (also known as Little Ten Curve) at Rocky, Colorado and will arrive in Denver within the hour.

Evidence of busting snow drifts on the Moffat coat the pilot on BNSF 5700 (ES44AC) as it leads a freight towards Denver, Colorado.

Eight GE and EMD locomotives are leading Union Pacific’s MNYRO westbound as it approaches Big 10 Curve between Rocky and Eisele, Colorado, on February 9, 2015.