When pianist Billy Strayhorn wrote “Take the A Train” for Duke Ellington’s orchestra, the final destination he had in mind was Harlem. The tune became the signature opening for Ellington, a reminder of home for thousands of American troops serving overseas during World War II. RTD’s cumbersomely named University of Colorado A Line – it cost CU $5 million for the “branded sponsorship” – is an A Train linking Union Station with DIA, covering 23 miles of commuter rail that can be traversed in 37 minutes.

With its April opening, Denver joined a growing number of American cities where travelers can take a train to a plane and back. Not all of these have proven a success. San Francisco’s BART extension provides access to nearly 10 million Bay Area residents, where daily commutes are frequently horrific and ridership has been high. Philadelphia, by contrast, runs virtually empty cars several times an hour.

After six years of construction, the A Line ribbon cutting drew plenty of Democratic and Republican politicians who could claim even a tangential connection to the project. Newly hired RTD General Manager David Genova assumes responsibility for keeping the A Line free of red ink operations. He introduced Gov. John Hickenlooper as the occasion’s first speaker, which was only appropriate.

Without Hickenlooper’s work as mayor of Denver on behalf of FasTracks in 2004, particularly corralling unanimous support from the Metro Mayors Caucus, it’s doubtful the A Line would have ever been built. Following the economic collapse of 2008, it became necessary to cobble together a public/private partnership – known in the field as a P3 – agreement for construction of the A Line and the Arvada-bound Gold Line. Australian bankers joined American construction firms to form Denver Transit Partners, ultimately delivering the air link on time and at the negotiated price. After an hour of repetitive exultations from mayors, members of Congress and U.S. Sen. Michael Bennet, a band played and Denver’s movers and shakers indulged in shameless self-congratulation before crowding onto the first train headed to Union Station.

For the rest of the weekend, A Line trains ran free for the curious. An estimated 85,000 residents took advantage of this offer, with kids and strollers in tow on family outings, crowding stations, overflowing parking lots and creating standing-room-only conditions on the commuter rail cars. Early Saturday morning, numerous of Denver’s homeless were also checking out the trains.

The link to DIA was one of the key selling points for the original FasTracks proposal and was certainly one of the more popular features of the entire system. A dirty little secret of that campaign, however, was the forecast that the A Line’s popularity did not match anticipated ridership. Until the remainder of the FasTracks build-out comes online during the next few years, and residents become comfortable with schlepping their luggage through the terminal hall at DIA, ridership may well prove anemic. As parking rates have climbed to $13 daily for the airport’s economy lots, a $9 rail fare begins to look more attractive. (The temptation to park your car and leave it for several days at the stations along the route seem likely to test their capacity except, perhaps, for the Central Park facility at Stapleton, the system’s largest.)

One of the first things you notice is that A Line commuter rail cars are far larger and heavier than the light rail vehicles we have grown familiar with. They are of a size and sturdiness similar to AMTRAK operations. These 70-ton behemoths are required by the Federal Rail Administration to ensure crash-worthiness whenever passenger transit shares a rail corridor with conventional freight operations. Their larger size also affords ample space for bicycle racks and stowing baggage.

For the Denver visitor headed downtown to attend a weeklong convention, the A Line will save on car rentals or taxi fares. But if visitors are headed north or south along the Front Range or into the mountains, its utility must await a high-speed rail line along I-25 and a MAGLEV monorail connecting Colorado’s central mountain resorts served by I-70. These multi-billion dollar projects will require the same patient political coalition-building that finally delivered FasTracks. RTD would be well advised to assist these efforts before demanding further expansion of a system that will require a decade to fully mature.