Raleigh is also served by Triangle Transit (known formerly as the Triangle Transit Authority, or TTA). Triangle Transit offers scheduled, fixed-route regional and commuter bus service between Raleigh and the region's other principal cities of Durham, Cary and Chapel Hill, as well as to and from the Raleigh-Durham International Airport, Research Triangle Park and several of the region's larger suburban communities. Triangle Transit also coordinates an extensive vanpool and rideshare program that serves the region's larger employers and commute destinations.