The sun pops out as BNSF SD60M No. 1404 leads an SD70MAC and SD40-2 on this westbound manifest as it rounds the big sweeping curve outside of Keenesburg, Colorado, on December 3, 2018.

Moments after sunset, an eastbound empty BNSF coal train races east along farm fields and US-6 just outside of Hillrose, Colorado, on December 4, 2018.

In the crisp cold air, the brakeman on the "Buck Local" is about to enter the depot in Longmont, Colorado, where the conductor is also grabbing some paperwork before heading south to Bou... (more)

It is just after sunset as BNSF ES44C4 No. 6764 leads a southbound manifest up the 2-percent grade to the top of Burkes Hill near Louisville, Colorado, on November 18, 2018.

After lining the siding switch up ahead reverse, the conductor has climbed aboard BNSF ES44C4 No. 6764 and will pull into the siding at Broomfield, Colorado, on November 18, 2018.

Some light snow has started to fall as BNSF ES44AC No. 5812 leads the Denver-Laurel manifest up Atwood Street in Longmont, Colorado, on November 11, 2018.

The brakeman on BNSF's Buck Local led by BNSF GP50 No. 3160 gets ready to sweep snow off the "GW Switch" before lining it reverse so the local can enter the main in Longmont, Colorado, o... (more)

Moments after sunset, Union Pacific ES44AC No. 7498 races west along US-30 just west of Bushnell, Nebraska along UP's Sidney Subdivision, on November 10, 2018.

After getting a new North Platte crew, Union Pacific ES44AC No. 5402 departs Cheyenne, Wyoming with an eastbound stack train, as it ducks under North College Drive, on October 20, 2018.

In the dawn hours of a cool and overcast morning, BNSF C44-9W No. 5018 leads a northbound loaded sand train up the middle of Atwood Street at Longs Peak Avenue, in Longmont, Colorado, on November ... (more)

A cold front from the north moved in overnight bringing the first measurable snow of the season across the Front Range. BNSF ES44C4 No. 6737 leads a southbound stack train up Berthoud Hill near Be... (more)

The fog has settled in as Union Pacific SD70AH No. 1943 leads an eastbound "Executive Special" out of the siding at Pinecliffe, Colorado after going through a Form B for a bridge replace... (more)

In the late afternoon sun, Union Pacific ES44AH No. 2591 races south with the Salt Lake City-Denver Z-Train while passing the big grain elevator in Platteville, Colorado, on October 3, 2018.

A brief dust storm moves through as a northbound loaded UP coal train from Energy Mine departs Platteville, Colorado, after meeting the ZLADV and ZSCDVX, on October 3, 2018.

After making its station stop in Granby, Amtrak's westbound "California Zephyr" snakes along the Colorado River in scenic Byers Canyon just west of Hot Sulphur Springs, Colorado, on Sept... (more)