seven underground Red Line stations (, , Park Street, Washington, , , and ) and three Orange Line stations. Six-car trains entered service on January 21, 1988. Central, Kendall/MIT, Park Street, and Downtown Crossing (renamed from Washington in 1987) were completed in 1988. A major reconstruction of JFK/UMass added a platform for the Braintree branch, which opened on December 14, 1988. Renovations to Broadway were completed in October 1989. and were accessible by 1989, if not from their original construction. South Station was completed around 1992, followed by Andrew in 1994. The 1990 passage of the Americans with Disabilities Act spurred the renovation of additional stations. was modified in 1991, followed by in 1998. Charles/MGH was rebuilt from 2003 to 2007. The agency began design for the four Ashmont branch stations in 2001. Savin Hill was closed from May 2004 to July 31, 2005 for reconstruction. It was followed by the completion of the rebuilt Fields Corner station in 2008, the modified Shawmut in 2009, and the rebuilt Ashmont in 2011. The final Red Line station to be modified for accessibility was , which was closed from January 2018 to August 2019 for a complete reconstruction. 2010s A $255 million project, which started in Spring 2013, replaced structural elements of the Longfellow Bridge, which carries the line across the Charles River between the Charles/MGH and Kendall/MIT stations. The project required at least 25 weekend shutdowns, including temporary relocation of the tracks and a substitute bus shuttle service. All outbound roadway traffic was detoured from the bridge for the three years of construction. The bridge finished construction in May 2018. On December 10, 2015, a Red Line train in revenue service traveled from to without an operator in the cab before it was stopped by cutting power to the third rail. The MBTA initially said that the train appeared to have been tampered with and the incident was not an accident, but later determined operator error to have been the cause. On February 21, 2018, a Red Line train motor failed on approach to Andrew station causing the train to derail. On June 11, 2019, a Red Line train derailed just north of JFK/UMass station, damaging three sheds of signal equipment that control the complex interlockings around the station. The Red Line was limited to 10 trains per hour (instead of the usual 13-14) for several months while repairs were made.