From the MTA:
The Second Avenue Subway will be New York City’s first major expansion of the subway system in over 50 years. When fully completed, the line will stretch 8.5 miles along the length of Manhattan’s East Side, from 125th Street in Harlem to Hanover Square in Lower Manhattan. In addition, a track connection to the existing 63rd Street and Broadway Lines will allow a second subway line to provide direct service from East Harlem and the Upper East Side to West Midtown via the Broadway express tracks.
In all, 16 new stations will be built, serving communities in Harlem, the Upper East Side, East Midtown, Gramercy Park, East Village, the Lower East Side, Chinatown and Lower Manhattan. The new stations will also provide transfers to other subway and commuter rail lines.
All of the stations will have escalator and elevator access including access for the disabled, and will feature climate control features to maximize customer comfort.