The "B" Branch, also called the Commonwealth Avenue Branch or Boston College Branch, is a branch of the MBTA Green Line light rail system which operates on Commonwealth Avenue west of downtown Boston, Massachusetts. One of four branches of the Green Line, the "B" Branch runs from Boston College station down the median of Commonwealth Avenue to Blandford Street. There, it enters Blandford Street Portal into Kenmore station, where it merges with the "C" and "D" branches. The combined services run into the Boylston Street Subway and Tremont Street Subway to downtown Boston. "B" Branch service currently terminates at Park Street; normally it runs to Government Center station which is undergoing renovations until 2016.