Beijing Metro is a rapid transit rail system that has served downtown Beijing and its outlying suburbs since 1969. Today, its four separate lines (Lines 1, 2, 5, and 13), traversing more than 122 kilometres, help about 2.6 million commuters get to their destinations every day. At more than 31 kilometres long, Line 1 is the longest east-west subway line in the system. Line 2, known as the "Loop Line," was built on the site of the original Beijing city wall and spans more than 23 kilometres to form a full loop around the city.
Anticipating the passenger surge that the 2008 Summer Olympic Games was sure to cause, Beijing Metro decided to upgrade two of its oldest and most used lines: Line 1 and Line 2. Beijing Metro's primary requirement was to modernise the existing station security systems with the latest and most reliable surveillance technology. This improvement project would affect 28 Line 1 stations and 20 Line 2 stations.
