The "D Line" refers to a specific route in the public transportation system of Denver, Colorado. It is part of the RTD Light Rail network, providing convenient access to various neighborhoods and key destinations in the city. The D Line runs from Union Station to Littleton, making several stops along the way. This line is popular among commuters and visitors alike, as it connects to other transit lines and offers easy access to downtown Denver and surrounding areas. The D Line operates frequently, making it a reliable option for those traveling within the city.