The Fourth and Madison Avenues Line is a public transit line in Manhattan, New York City, United States, running mostly along Park Avenue and Madison Avenue from Lower Manhattan to Harlem. Originally a streetcar line, it is now the M1 bus, operated by the Manhattan and Bronx Surface Transit Operating Authority out of the Mother Clara Hale Bus Depot. The M1 bus now runs southbound on Fifth Avenue rather than Madison Avenue north of 40th Street.