A drone carrying a QR code placard is seen near an expressway toll station in Shenzhen, south China's Guangdong Province, Feb. 11, 2020. As a measure to help prevent and control novel coronavirus, an online register system for vehicles coming back to Shenzhen has been put into use since Feb. 8. To increase the efficiency, local police officers used drones to carry a QR code at the expressway exits for drivers to get registered with less contact with other people. (Photo by Lai Li/Xinhua)

A drone carrying a QR code placard is seen near an expressway toll station in Shenzhen, south China's Guangdong Province, Feb. 11, 2020. As a measure to help prevent and control novel coronavirus, an online register system for vehicles coming back to Shenzhen has been put into use since Feb. 8. To increase the efficiency, local police officers used drones to carry a QR code at the expressway exits for drivers to get registered with less contact with other people. (Photo by Lai Li/Xinhua)

A police officer operates a drone carrying a QR code placard near an expressway toll station in Shenzhen, south China's Guangdong Province, Feb. 11, 2020. As a measure to help prevent and control novel coronavirus, an online register system for vehicles coming back to Shenzhen has been put into use since Feb. 8. To increase the efficiency, local police officers used drones to carry a QR code at the expressway exits for drivers to get registered with less contact with other people. (Photo by Lai Li/Xinhua)

A drone carrying a QR code placard is seen near an expressway toll station in Shenzhen, south China's Guangdong Province, Feb. 11, 2020. As a measure to help prevent and control novel coronavirus, an online register system for vehicles coming back to Shenzhen has been put into use since Feb. 8. To increase the efficiency, local police officers used drones to carry a QR code at the expressway exits for drivers to get registered with less contact with other people. (Photo by Lai Li/Xinhua)