Following a shadowed Colorado River, Amtrak’s westbound California Zephyr has just passed through Tunnel 39 in Little Gore Canyon west of Azure, Colorado, on November 3, 2010.

A trio of UP's hug the side of Little Gore Canyon as they lead an empty rail train east while some fisherman try to snag some trout out of the Colorado River.

After waiting in the siding at Azure for the westbound California Zephyr, Rio Grande Train 138 starts moving eastward toward Denver.

About to enter Little Gore Canyon is Amtrak No. 5, the westbound California Zephyr, cruising west of Azure, Colorado, along the Colorado River on August 20, 2014.

Amtrak No. 6, the eastbound California Zephyr, slinks along the Colorado River through Little Gore Canyon west of Azure, Colorado, on August 21, 2014.

The low winter sun has risen enough to illuminate the rails for the passage of westbound Rio Grande train #187. Tunnel Motor #5404 leads the 5 unit set.

Amtrak’s westbound California Zephyr passes through 294-foot Tunnel 39 along the Colorado River in Little Gore Canyon between Azure and Radium, Colorado, on the afternoon of August 3, 2014.

While two people in a lone raft enjoy the Colorado River, a westbound Union Pacific coal empty thunders out of Tunnel 39 in Little Gore Canyon west of Azure, Colorado, on the afternoon of August 2... (more)

The westbound California Zephyr winds through Gore Canyon with the Veterans and Phase 1 teamed up.

On a stormy summer afternoon, the sound of a loaded coal train bounces off the walls of Little Gore Canyon. This heavy train is working its way up the Western Slope of the Rocky Mountains. Soon th... (more)

Emerging from the clouds into a little sunshine, the westbound Rio Grande Zephyr approaches Tunnel 39 and prepares to enter Little Gore Canyon.

Colorado's Western Slope is home to gritty mountain railroading. Heavy trains, deep canyons and treacherous curves are common along this route. Here, a loaded coal train running 2x2x2 thunders thr... (more)

A Union Pacific hi-rail vehicle pops out of Tunnel 39 in Little Gore Canyon while inspecting the rugged Moffat Tunnel Subdivision main line between trains west of Azure, Colorado, on August 21, 20... (more)

The lead locomotives of an eastbound Union Pacific coal train enjoy a bit of tangent track in Little Gore Canyon west of Axure, Colorado, on August 20, 2014. The blue smoke in the canyon is being ... (more)

A Union Pacific coal train approaches 63-foot Tunnel 40 in scenic Little Gore Canyon west of Azure, Colorado, on the afternoon of August 21, 2014.