Phase 4 extension to Suwon's Homaesil and Hwaseo Station is currently undergoing economic viability assessments by the government, with Suwon City saying that results should be positive when it comes out. From Gangnam Station, trains are available from 5:30am until 24:50 midnight on weekdays, cut to 11:48pm on weekends and public holidays. However, the last train to Gwanggyo departs at 24:26 on weekdays, cut to 23:48 on weekends, with the remainder going until Jeongja Station only. The trains are automated and run every 2.5 minutes during peak times to 8 minutes during off-peak hours. The SBL Line signal system is based on state-of-the-art communications-based train control (CBTC) technology, utilizing two-way digital radio communications between intelligent trains, and wayside equipment, and a network of ATS/ATO computers designed for very high system reliability and availability. Platforms can accommodate 10-car trains at 200 meters but initially 6-car trains will be used. Phase 1 was opened on October 28, 2011, and spans from Gangnam to Jeongja. Phase 2 was opened on January 30, 2016, extending the line by 6 stations from Jeongja to Gwanggyo. Migeum Station opened in April 2018, offering a transfer to the Bundang Line. Construction of Phase 3 began in March 2017 between Sinsa and Gangnam, slated for opening on January 29, 2022. Although initially planned to be opened simultaneously with the Sinsa-Gangnam extension, due to the extension from Sinsa to Yongsan potentially sharing tracks with the newly approved GTX A line towards Ilsan, construction will initially begin in 2016 between Sinsa and Gangnam only, slated for opening on January 29, 2022. The stations between Sinsa and Yongsan are to be determined when the Yongsan Garrison moves out and becomes a public park, with plans to split it at Dongbinggo to Noksapyeong Station, Seoul Station, City Hall Station, Gwanghwamun Station, Gyeongbokgung Station, terminating at Samsong Station in Goyang. However, the Yongsan extension will begin construction earlier than the Samsong extension, as the latter has not been evaluated yet. The southwestern extension to Homaesil passed the economic feasibility research in late 2019. It is expected that construction will begin in 2023, with opening potentially in 2027, given that construction usually take 5 years to complete.