The rear DPUs of a loaded coal roll through the morning fog.

Sunlight and dense fog combine to create a unique phenomenon known as a fog rainbow, creating a 'tunnel' through which the loaded coal train ran.

Dense fog at sunrise catches BNSF 5783 (ES44AC) as it heads to Denver on the Moffat Tunnel Sub.

BNSF 9038 (SD70ACe) runs through a cold and snowy Tonville, Colorado as it heads to Denver on the Brush Sub.

BNSF 4208 (ES44C4) leads a freight through Tonville, Colorado as it heads west on the Brush Sub.

BNSF 9038 (SD70ACe) leads a loaded coal train past the signals at Tonville, Colorado as it heads to Denver on the Brush Sub.

BNSF 4208 (ES44C4) leads the Z Train through Tonville, Colorado on the Brush Sub.

BNSF 3648 (ET44ACH) leads a coal train through Tonville, Colorado on its way to Denver, on the Brush Sub.

Sub-freezing morning temperatures greet BNSF 8543 (SD70ACe) as it leads a coal train through Tonville, Colorado on the Brush Sub.

BNSF 6616 (ES44C4) is bathed in an orange glow from a spectacular Colorado sunrise on the Brush Sub.

BNSF 9161 (SD70ACe) leads a freight past a grain train sitting on the siding at Tonville, Colorado.

BNSF 3640 (ET44ACH) shoves a loaded coal through Tonville, Colorado on the Brush Sub.

BNSF 7134 (ES44C4) leads a Grinstein and a freight through Tonville, Colorado on the Brush Sub.

A dynamic sunrise catches BNSF 5915 (ES44AC)) running a loaded coal train past a frozen pond at Tonville, Colorado.

Coal is still king on the Brush Sub as BNSF 5819 (ES44AC) leads a loaded train towards Denver, Colorado.