The Colorado Northern is a fictional bridge line running north from Craig, CO to interchange with the Union Pacific near Green River, WY.  The Rio Grande runs from Denver to Craig, but terminates there; this bridge line gives the Rio Grande a more direct route to the Pacific Northwest, as well as direct access to the Wyoming coal fields. The Rio Grande provides Denver-Craig passenger service via the Yampa Valley, also know as trains 9 and 10, a short train typically consisting of a PA locomotive, a baggage or baggage-mail car, and a coach. The exact makeup depends on what equipment happens to be available. The Colorado Northern provides passenger service from Craig to Green River.  The two railroads have a power pool agreement, so Rio Grande locomotives are often seen in service on Colorado Northern rails.