A staff member holds a placard to remind passengers to show their health codes at a bus station in Beijing, May 17, 2022. (Photo: China News Service/Han Haidan) Starting Tuesday, passengers should show their green health codes before boarding buses and entering subway stations around the locked-down and controlled zones in Beijing. These measures involve 190 bus lines and 54 subway stations.

A staff member checks a passenger's health code at a bus station in Beijing, May 17, 2022. (Photo: China News Service/Han Haidan)

An epidemic prevention announcement is posted on a bus window to remind passengers to show their health codes, Beijing, May 17, 2022. (Photo: China News Service/Han Haidan)

A woman shows her green health code before entering a subway station in Beijing, May 17, 2022. (Photo: China News Service/Han Haidan)