Rapid transit line under planning in Beijing
Line 20 of the Beijing Subway (), or Line R4 (Chinese: 北京地铁R4线; pinyin: "běijīng dìtiě R sì xiàn") is a rapid transit line under planning in Beijing.
The first phase of Line 20 will be 21.3 km in length with 5 stations.
It is expected to open in 2028. There will be through service between Line 3 and Line 20.
History.
In 2019, Liu Xuesong, representative of the Beijing Municipal People's Congress and general manager of Capital Airport Holding, suggested building the northern section of the line in advance. 
On November 10, 2020, the Shunyi Branch of the Beijing Municipal Planning and Natural Resources Commission released a notice to advance the preliminary work of rail transit, including the Shunyi section of Line 20.
According to the information released on January 11, 2022, the first phase of the line is included in the "Beijing Rail Transit Phase III Construction Plan". On 8 July 2022, the EIA of Phase III Plan announced that it will be a line, with 4 stations from in Chaoyang District to in Shunyi District.
On 17 June 2024, Beijing Infrastructure Investment published their first EIA analysis, confirmed that phase 1 of line 20 will have 5 stations. Later on 27 August, their second EIA analysis said that there will introduce through trains with line 3 and line 12, as well as Linhe is an elevated station, the depot is tentatively named Zhuangtoucun Depot that located north of Jian River.
References.
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