Line 18 is a north–south Shanghai Metro line running from South Changjiang Road station in the city's Baoshan District to Hangtou station in Pudong, with a length of 36.13 km (22.45 mi). The line was originally scheduled to open by the end of 2020. However, officials announced that only the initial segment of eight stations in Pudong started test runs in September 2020. The 14.5 km (9.0 mi) southern section opened for passenger operations on December 26, 2020. The remainder of the line was opened on 30 December 2021. The line is 36.5 km (22.7 mi) long with 26 stations. The line is one of Shanghai Metro's new batch of high capacity fully automated and driverless lines along with Lines 14 and 15. The line is colored earth yellow on system maps.

Line 3 is a north–south line of the Shanghai Metro network. Its older rolling stock carry a bright yellow colour belt to differentiate them from Line 4 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”. Unlike the majority of the lines in the Shanghai Metro system, Line 3 is primarily elevated, entirely above ground except for Tieli Road, located at the entrance to Baosteel Group Corporation. The line runs from North Jiangyang Road in the north to Shanghai South Railway Station in the southwest of the city, where it meets line 1. While line 1 goes straight through the city center, line 3 roughly follows the Inner Ring Road around the city from Caoxi Road to Zhongtan Road. The line has about 300 drivers. Between December 26, 2000, and August 8, 2002, the line operated under the name Pearl Line; On August 8, 2002, it was renamed as Rail Transit Line 3. The line is colored yellow on system maps.