Head house
Head house is an American railroad term for the part of a train station which does not house the tracks and platforms. Outside America, the same part of a station is known as the station building. In the context of rail transport, the term head house usually refers to the portion of a large passenger terminal which contains the ticket counters, waiting rooms, toilets and baggage facilities. It might also include the passenger concourses and walkways between the platforms and other facilities.
Purpose
Larger terminals had amenities that were contained within their own distinct building which was separate to the railroad. For instance, when Cincinnati Union Terminal opened in 1933, the head house held a restaurant, lunch room, ice cream shop, news agent, drug store, small movie theater, men's and women's lounges, and restrooms that included changing rooms and showers.
Subways
In the context of subways, a head house refers to the part of a subway station that is above ground, which may be nothing more than a covered entrance. The head house may contain escalators, elevators and ticket agents.