to loop at Government Center. Regular use of PCC cars on the D branch ended March 23, 1978, though later LRV shortages prompted the occasional return of PCC streetcars. The downtown terminal was again changed several times from 1980 to 1984; after January 20, 1984, D branch trains terminated at Government Center at rush hours and Lechmere at other times. Rush hour service was cut back to Government Center on June 20, 1987. Riverside station on the D branch is located about southeast of the station on the mainline, which saw commuter rail service until 1977. The tracks between the two stations were largely disused by the 1960s, though they were used for LRV deliveries in the 1970s. On October 20, 1996, flooding from the Muddy River inundated the Green Line subway. D branch trains only ran between Riverside and Brookline Village until October 27, when they were extended to Park Street. Special commuter rail shuttle trains also ran between South Station and a temporary platform near the Riverside light rail station from October 23–25 to supplement Green Line service. Weekend D branch service was extended to Lechmere on March 28, 1997; weekday service followed on June 21. It was cut back to Government Center on June 19, 2004, to accommodate the demolition of the Causeway Street elevated and the opening of the new underground North Station. Green Line service to Lechmere resumed on November 12, 2005, though the D branch continued to terminate at Government Center. 21st century The tracks were rehabilitated again in 2007 because new Type 8 LRVs did not operate reliably at the desired speeds. Unlike previous rolling stock, the D branch was the last to get the new LRvs due to the need to upgrade the tracks. Shuttle buses replaced rail service between Riverside and Reservoir from June 23 to August 3, 2007, and between Reservoir and Fenway from August 4–31. On May 28, 2008, two trains collided between and stations, killing the operator of the rear train. The National Transportation Safety Board investigation concluded that the operator likely had an episode of micro-sleep caused by sleep apnea. On October 25, 2010, the MBTA began operating some three-car trains on the D branch at peak hours. This was expanded on March 21, 2011, but was discontinued on March 21, 2016, in favor of operating two-car trains on more consistent headways. On March 22, 2014, Government