From SFMTA :
The SFMTA began Third Street T Line service between Embarcadero and Sunnydale in 2007. Upon completion of the Central Subway, the Mission Bay Loop will allow for more frequent service between Mission Bay, SOMA and Chinatown by finishing the train turnaround at Third, 18th, 19th and Illinois Streets. Transit frequency south of Mission Bay will also be increased.
SFMTA is now completing the required federal Environmental Assessment. We are eager to hear your thoughts about the project and to update you on the proposed schedule, with construction anticipated for 2014.