A passenger checks in to take the test-run Rail Transit Line 3 in Hefei City, east China's Anhui Province, Dec. 18, 2019. The Rail Transit Line 3 started test runs Wednesday and was open to the public for free during the test period lasting to Dec. 22. It was scheduled to be put into official operation by the end of this month. (Xinhua/Zhou Mu)

  Passengers wait to take the test-run Rail Transit Line 3 in Hefei City, east China's Anhui Province, Dec. 18, 2019. The Rail Transit Line 3 started test runs Wednesday and was open to the public for free during the test period lasting to Dec. 22. It was scheduled to be put into official operation by the end of this month. (Xinhua/Zhou Mu)

  A staff member helps a passenger scan a code with mobile app to take the test-run Rail Transit Line 3 in Hefei City, east China's Anhui Province, Dec. 18, 2019. The Rail Transit Line 3 started test runs Wednesday and was open to the public for free during the test period lasting to Dec. 22. It was scheduled to be put into official operation by the end of this month. (Xinhua/Zhou Mu)

  Passengers take the test-run Rail Transit Line 3 in Hefei City, east China's Anhui Province, Dec. 18, 2019. The Rail Transit Line 3 started test runs Wednesday and was open to the public for free during the test period lasting to Dec. 22. It was scheduled to be put into official operation by the end of this month. (Xinhua/Zhou Mu)