Various extensions and branches were added at both ends, bypassing more surface tracks. As grade-separated lines were extended, street-running lines were cut back for faster downtown service. The last elevated heavy rail or "El" segments in Boston were at the extremities of the Orange Line: its northern end was relocated in 1975 from Everett to Malden, Massachusetts, and its southern end was relocated into the Southwest Corridor in 1987. However, the Green Line's Causeway Street Elevated remained in service until 2004, when it was relocated into a tunnel with an incline to reconnect to the Lechmere Viaduct. The Lechmere Viaduct and a short section of steel-framed elevated at its northern end remain in service, though the elevated section was cut back slightly and connected to a northwards viaduct extension as part of the Green Line Extension.
Various extensions and branches were added at both ends bypassing more surface tracks As grade-separated lines were extended street-running lines were cut back for faster downtown service The last elevated heavy rail or "El" segments in Boston were at the extremities of the Orange Line its northern end was relocated in 1975 from Everett to Malden Massachusetts and its southern end was relocated into the Southwest Corridor in 1987 However the Green Line's Causeway Street Elevated remained in service until 2004 when it was relocated into a tunnel with an incline to reconnect to the Lechmere Viaduct The Lechmere Viaduct and a short section of steel-framed elevated at its northern end remain in service though the elevated section was cut back slightly and connected to a northwards viaduct extension as part of the Green Line Extension