BEIJING, July 18 (Xinhua) -- Platform screen doors were installed at Yong'anli Station on Beijing's subway Line 1 on Monday to protect passengers of one of the world's busiest metro networks.

The 1.5 m-tall metal and glass doors are the first barriers for China's oldest subway line, which started operations in 1971.

Builders reinforced the platform before installing the doors. By the end of 2017, the remaining 22 stations on the line will all have screen doors.

Currently, only Line 1 and Line 2 of Beijing's 18 subway routes have no protective barriers. The public has called for screen doors as occasional suicides and accidents have raised safety concerns.