Line 4 is a loop line of the Shanghai Metro network. Its older rolling stock carry a bright purple colour belt to differentiate them from Line 3 trains which share a portion of its route, while the newer stock features a yellow and purple livery, which the exact line is labelled using sticker or screens saying “Line 3” or “Line 4”. To determine the direction of travel, the line that travels counter-clockwise is called the Outer Loop (), while the other line is known as the Inner Loop (). Although it is a loop line, trains returning to the depot use as a terminal to let all passengers disembark. The first segment of the line between and (running in a "C"-shape) opened on December 31, 2005. The remainder of the line opened on December 29, 2007. The line is colored purple on system maps. History October 11, 2009 became China's first national "Worker Pioneer" subway line. Construction accident On August 20, 2001 on 20.10 at construction site during excavating the foundation pit, earthmoving sudden landslide, killing four people died who were buried in the landslide. At 4 o'clock in the morning on July 1, 2003, the Pudongnan Road-Nanpu Bridge section of Line 4 suddenly saw water seepage during the construction of the connecting passage between the upper and lower tunnels. After that, a large amount of quicksand poured into the tunnel, causing internal and external pressure imbalance, which caused partial collapse of the tunnel. It has a funnel-shaped settlement. At 9 o'clock in the morning, the podium of a nearby building on South Zhongshan Road collapsed; beginning in the early morning of the July 2, the flood wall of Dongjiadu Waima Road section began to sink and crack due to the settlement. The embankment collapsed in a serious accident. The Linjiang Garden Building near the scene also experienced subsidence, the most serious settlement exceeded 7 millimeters in an hour, and the cumulative settlement reached 15.6 millimeters. This incident affected the plan for the opening of the entire line of Line 4. In August 2004, the Dongjiadu section restoration project was started and it was restored with the opening of the second section in July 2007. On November 5, 2004, the Shanghai Second Intermediate People’s Court issued a judgement on the deputy project manager of the subcontractor for the construction of the intermediate air shaft and side channel freezing method. The