Penn Central itself went bankrupt the next year, and the station building was closed in 1973 to cut costs, leaving only the under-track 'subway' open for passengers.

The large waiting room is thirty-five feet high and features models of NYNH&HRR trains on the benches.

Located at the intersection of the Northeast Corridor and the New Haven–Springfield Line, the station serves a variety of train services, including Amtrak, CT Rail, and Metro-North.

The southern platform is adjacent to Tracks 12 and 14, usually serves Metro-North and Shore Line East, and can accommodate 8-car trains.

Track 6, not adjacent to any platform in the center of the station, is used only by through trains or idling Shore Line East consists.

[8] Amtrak runs frequent service through Union Station along the electrified Northeast Corridor rail line.

[10] These through trains must change locomotives at New Haven, as the track north to Springfield is not electrified, unlike the Northeast Corridor.

Prior to 2000, when the Northeast Corridor was electrified all the way to Boston, all trains continuing north of Union Station had to change from diesel to electric power.

Because of United Airlines code sharing on select Amtrak trains between Union Station and its hub at Newark Liberty International Airport in the New York City area,[12] Union Station is assigned the IATA airport code of ZVE.

[17] Metro-North Railroad operates its New Haven Line from Union Station to Grand Central Terminal in New York City.

Shore Line East and Metro-North work together on schedules to provide quick transfers of trains for commuters traveling from the Shoreline to Grand Central Terminal or Stamford.

A select number of trains start or end their run two minutes to the east at New Haven State Street.

[19] On April 20, 2020, the station became the indefinite western terminus for Shore Line East service, running on a limited schedule due to the coronavirus pandemic.

[27] Following the Second World War, railroads faced increasing competition from airlines and automobiles, and passenger train service declined.