An eastbound Union Pacific coal train meets a BNSF manifest freight in the siding at Rocky, Colorado, on the afternoon of June 28, 2014.

Amtrak No. 5, the westbound California Zephyr, is climbing the grade toward Big 10 Curve west of Rocky, Colorado, on September 6, 2001. In the background waiting in the siding at Clay is an eastbo... (more)

BNSF units 5634, 4063, 4902, 232 and 6208 lead a train of mixed freight up the grade out of Rocky, CO., on a beautiful summer morning.

BNSF units 5634, 4063, 4902, 232 and 6208 lead a train of mixed freight around the Big Ten Curve and a warm summer morning.

With the city of Denver and the plains of eastern Colorado in the background, a BNSF manifest freight departs Rocky on the clear afternoon of June 28, 2014.

Afternoon sun glints off the last cars of a late-running Amtrak No. 5 as it climbs out of Rocky, Colorado, on December 5, 2014.

Union Pacific’s west local has just come off of Rocky Spur and slowly heads east on the main while a westbound coal train passes on the siding at Rocky, Colorado, on March, 16, 2011.

In March of this year Amtrak did a trial run of the legendary Ski Train which shuttled skiers from Denver's Union Station to Winter Park in the morning and then back again in the evening. The tes... (more)

AMTK 93 has just rounded Big 10 Curve and heads towards tunnel No 1 on the Moffat Line. Notice anything missing?

As the rear of an eastbound Union Pacific coal train heads through Rocky, Colorado, below—an eastbound BNSF manifest freight passes through Tunnel 1 in the background on August 11, 2015. The rea... (more)

As the sun sets behind the front range of the Rockies, a westbound Union Pacific coal train negotiates Big 10 Curve between Rocky and Eisele (formerly Clay), Colorado. The City of Denver can be se... (more)

Amtrak’s westbound California Zephyr climbs the front range of the Rockies as it leaves Rocky, Colorado, and heads toward Big 10 Curve on August 11, 2015.

A patched SP unit brings up the rear of the Denver - Salt Lake City manifest at Rocky, CO.

The westbound California Zephyr starts its climb up the Rocky Mountains as a dense patch of fog begins to lift along the foothills.

Another loaded coal train descends around the Big 10 curve.