The Green Line is a light rail system run by the Massachusetts Bay Transportation Authority (MBTA) in the Boston, Massachusetts metropolitan area. It is the oldest Boston subway line, with tunnel sections dating to 1897. It runs underground through downtown Boston, and on the surface on several radial boulevards and into inner suburbs. With a daily weekday ridership of 210,000 in early 2014, it is the second most heavily-used light rail system in the country. The line was assigned the green color in 1967 during a systemwide rebranding because several branches pass through sections of the Emerald Necklace of Boston.