I agree Brian. The Denver RTD Commuter Rail is a true electrified commuter rail operation (not transit/light rail) and the first in the far west. You might see something similar in Chicago with METRA and NICTD.
In addition to both ATK and RTD Commuter Rail, Denver Union Station (DUS) is also the transit hub for the RTD city and commuter bus system for the Denver Metro Area. The RTD Light Rail Trains arrive at a platform at the other end of the plaza from DUS. The light rail platform and DUS is connected by an underground transit concourse which allows access to not only the buses, but also all tracks at DUS for both ATK and commuter operations.
It is fun to hang around DUS and watch the commuters come and go and see what ATK may be setting out or have on the end of the train. The new Winter Park Express Ski Train will be starting weekend service on January 7th, bringing more activity to DUS.
MDR