The Park Avenue main line, which consists of the Park Avenue Tunnel and the Park Avenue Viaduct, is a railroad line in the New York City borough of Manhattan, running entirely along Park Avenue. The line carries four tracks of the Metro-North Railroad as a tunnel from Grand Central Terminal at 42nd Street to a portal at 97th Street where it rises to a viaduct north of 99th Street and continues over the Harlem River into the Bronx over the Park Avenue Bridge. During rush hours, Metro-North uses three of the four tracks in the peak direction.