to its current terminus at Balboa Park. In 1991, the J Church was extended from Church and 30th Streets to its current terminus at Balboa Park. In 1998, the N Judah was extended from Embarcadero Station to the planned site of the new Pacific Bell Park and Caltrain Depot, The extension was briefly served between January and August of that year by the temporary E Embarcadero light rail shuttle (restored in 2015 as the E Embarcadero heritage streetcar line). In 2007, the T Third Street, running south from Caltrain Depot along Third Street to the southern edge of the city, opened as part of the Third Street Light Rail Project. Limited weekend T line service began on January 13, 2007, while full service began on April 7, 2007. The line initially ran from the southern terminus at Bayshore Boulevard and Sunnydale Street to Castro Street Station in the north. The line ran into initial problems with breakdowns, bottlenecks, and power failures, creating massive delays. Service changes to address complaints with the introduction of the T Third Street were implemented on June 30, 2007, when the K and T trains were interlined, or effectively merged into one single line with route designations changing at the entrances into the subway (T becomes K outbound at Embarcadero; K becomes T inbound at West Portal). The Central Subway runs between Chinatown station in Chinatown and a portal in South of Market (SoMa), with intermediate stops at Union Square/Market Street station in Union Square and Yerba Buena/Moscone station in SoMa. A surface portion runs through SoMa to connect to the existing T Third Street line at 4th and King station. Muni estimates that the Central Subway section of the T Third Street line will carry roughly 35,100 riders per day by 2030. Originally set to open in late 2018, the subway opened with weekend-only shuttle service on November 19, 2022. Full service as part of the T Third Street line began on January 7, 2023. Additional shuttle trains signed "S Chase Center" will operate between Chinatown and for events at Chase Center. COVID-19 pandemic On March 30, 2020, Muni Metro service was replaced with buses due to the COVID-19 pandemic. The SFMTA reopened rail service on August 22, 2020, but returned to bus substitution three days later, citing malfunctioning overhead wire splices and the need to quarantine control center staff after a COVID-19 case. During