Aerial photo taken on Dec. 23, 2020 shows a portal crane assembling track sections at the construction site of Shaoguang Station of the Changsha Subway Line 6 in Changsha, central China's Hunan Province. The construction of the Changsha Subway Line 6 entered the phase of track laying Wednesday. The 48.11-kilometer line with 34 stations will serve as an east-west aorta of urban transportation in Changsha, and is expected to start pilot operation before the end of 2021. (Xinhua/Chen Sihan)

A worker operates a track-laying machine at the construction site of Shaoguang Station of the Changsha Subway Line 6 in Changsha, central China's Hunan Province, Dec. 23, 2020. The construction of the Changsha Subway Line 6 entered the phase of track laying Wednesday. The 48.11-kilometer line with 34 stations will serve as an east-west aorta of urban transportation in Changsha, and is expected to start pilot operation before the end of 2021. (Xinhua/Chen Sihan)

A worker is engaged in track-laying operation at the construction site of Shaoguang Station of the Changsha Subway Line 6 in Changsha, central China's Hunan Province, Dec. 23, 2020. The construction of the Changsha Subway Line 6 entered the phase of track laying Wednesday. The 48.11-kilometer line with 34 stations will serve as an east-west aorta of urban transportation in Changsha, and is expected to start pilot operation before the end of 2021. (Xinhua/Chen Sihan)

Workers operate a track-laying machine at the construction site of Shaoguang Station of the Changsha Subway Line 6 in Changsha, central China's Hunan Province, Dec. 23, 2020. The construction of the Changsha Subway Line 6 entered the phase of track laying Wednesday. The 48.11-kilometer line with 34 stations will serve as an east-west aorta of urban transportation in Changsha, and is expected to start pilot operation before the end of 2021. (Xinhua/Chen Sihan)

Aerial photo taken on Dec. 23, 2020 shows a portal crane assembling track sections at the construction site of Shaoguang Station of the Changsha Subway Line 6 in Changsha, central China's Hunan Province. The construction of the Changsha Subway Line 6 entered the phase of track laying Wednesday. The 48.11-kilometer line with 34 stations will serve as an east-west aorta of urban transportation in Changsha, and is expected to start pilot operation before the end of 2021. (Xinhua/Chen Sihan)

Workers assemble track sections at the construction site of Shaoguang Station of the Changsha Subway Line 6 in Changsha, central China's Hunan Province, Dec. 23, 2020. The construction of the Changsha Subway Line 6 entered the phase of track laying Wednesday. The 48.11-kilometer line with 34 stations will serve as an east-west aorta of urban transportation in Changsha, and is expected to start pilot operation before the end of 2021. (Xinhua/Chen Sihan)