If you were in Denver this weekend, you might’ve seen an unusual sight: A MARC commuter rail train parked behind Denver Union Station.

MARC in Denver. Photo by Ryan Dravitz.

What gives?

Turns out the train was in Colorado as part of the testing for MARC’s new locomotives. Officials wanted to test the new locomotives with actual MARC rolling stock, to evaluate how the locomotives performed in real-life conditions.

The Federal Railroad Administration has a test track in Pueblo, CO, so off this train went.

The train was in Denver because Amtrak carries the equipment on a regularly scheduled train from Denver to Chicago (#5, the California Zephyr) and then from Chicago to DC (#29, the Capitol Limited).

Thanks to Matt Johnson and Twitter user @kencon06 for helping to solve this mystery.

 Comment on this at the version cross-posted to Greater Greater Washington.