A technician maintains the electric system of a subway line in east China's Shanghai, May 5, 2022. Routine maintenance work for subways in the city has been carried out to ensure good condition of facilities. (Xinhua/Chen Jianli)

　　A worker maintains facilities of a subway driving cab in east China's Shanghai, May 5, 2022. Routine maintenance work for subways in the city has been carried out to ensure good condition of facilities. (Xinhua/Chen Jianli)

　　Workers maintain subway tracks in east China's Shanghai, May 5, 2022. Routine maintenance work for subways in the city has been carried out to ensure good condition of facilities. (Xinhua/Chen Jianli)

　　A sanitation worker disinfects subway carriages in east China's Shanghai, May 5, 2022. Routine maintenance work for subways in the city has been carried out to ensure good condition of facilities. (Xinhua/Chen Jianli)

　　A technician maintains traffic lights of subway lines in east China's Shanghai, May 5, 2022. Routine maintenance work for subways in the city has been carried out to ensure good condition of facilities. (Xinhua/Chen Jianli)

　　Workers maintain subway tracks in east China's Shanghai, May 5, 2022. Routine maintenance work for subways in the city has been carried out to ensure good condition of facilities. (Xinhua/Chen Jianli)

　　A maintenance worker examines a subway carriage in east China's Shanghai, May 5, 2022. Routine maintenance work for subways in the city has been carried out to ensure good condition of facilities. (Xinhua/Chen Jianli)

　　A staff member disinfects the Renmin Square subway station, which is now under closed-off management, in east China's Shanghai, May 5, 2022. Routine maintenance work for subways in the city has been carried out to ensure good condition of facilities. (Xinhua/Chen Jianli)

　　A technician maintains a subway train in east China's Shanghai, May 5, 2022. Routine maintenance work for subways in the city has been carried out to ensure good condition of facilities. (Xinhua/Chen Jianli)