The Skycar (or can be referred to as the cable car) is an aerial tramway in Grand Theft Auto IV.
The Skycar is an aerial tramway that connects Lancet, Algonquin to Colony Island in the Grand Theft Auto IV rendition of Liberty City, just south of the Algonquin Bridge. The tramway falls under the management of the Liberty City Transport Authority (LTA) and is dubbed "The Pigeon", similar to "The Fox" nickname stamped onto GTA IV's buses.
The player can take a ride on the trams, though they cannot see anything or do anything. First person view can be accessed through a mobile phone with camera capabilities. Apparently no pedestrians are programed to use the skycar. It is possible for the player to hold onto the tram in the station, but once it takes off, the player character just lets go, making it literally impossible to vehicle surf on it (much like all other vehicles in the game).
The tram link is evidently based on the Roosevelt Island Tramway between Manhattan and Roosevelt Island in New York City. As such, the tram cars, stations, and cable pylons share a likeness with the real-life rendition.
A pigeon is located at the Lancet station and is clearly visible when Niko offloads from the tram.