| Line 15 | Line 15 (Beijing Subway) | Line 15 (BMT) |
| Line 15 (Chongqing Rail Transit) | Line 15 (disambiguation) | Line 15 (IndyGo) |
| Line 15 (Moscow Metro) | Line 15 (Philadelphia) | Line 15 (Sao Paulo Metro) |
| Line 15 (São Paulo Metro) | Line 15 (Shanghai Metro) | Line 15 (Shenzhen Metro) |
| Line 15 (Xi'an Metro) | Line 15 (Zürich) | Line 15, Beijing Subway |
| Line 15, Shanghai Metro | Line 16 | Line 16 (2000 scheme) |
| Line 16 (Beijing Subway) | Line 16 (BMT) | Line 16 (defunct) |
| Line 16 (disambiguation) | Line 16 (Guangzhou Metro) | Line 16 (Hangzhou Metro) |
| Line 16 (IndyGo) | Line 16 (Sao Paulo Metro) | Line 16 (São Paulo Metro) |
| Line 16 (Shanghai Metro) | Line 16 (Shenzhen Metro) | Line 16 (Wuhan Metro) |
| Line 16 (Xi'an Metro) | Line 16 (Zürich) | Line 16, Beijing Subway |
| Line 16, Hangzhou Metro | Line 16, Shanghai Metro | Line 16, Shanghai Metro (old) |
| Line 16, Wuhan Metro | Line 161 (Infrabel) | Line 16X, Shanghai Metro |
| Line 17 | Line 17 (Beijing Subway) | Line 17 (Chengdu Metro) |
| Line 17 (defunct) | Line 17 (disambiguation) | Line 17 (Hangzhou Metro) |
| Line 17 (Sao Paulo Metro) | Line 17 (São Paulo Metro) | Line 17 (Shanghai Metro) |
| Line 17 (Shenzhen Metro) | Line 17 (Stockholm metro) | Line 17 (Stockholm Metro) |
| Line 17 (Stockholm Tunnel Rail) | Line 17 (Zürich) | Line 17 (Zhengzhou Metro) |
| Line 17, Beijing Subway | Line 17, Shanghai Metro | Line 17, Shanghai Metro (old) |
| Line 18 | Line 18 (Beijing Subway) | Line 18 (Chengdu Metro) |
| Line 18 (Chongqing Rail Transit) | Line 18 (disambiguation) | Line 18 (Guangzhou Metro) |
| Line 18 (IndyGo) | Line 18 (Sao Paulo Metro) | Line 18 (São Paulo Metro) |
| Line 18 (Shanghai Metro) | Line 18 (Shenzhen Metro) | Line 18 (Stockholm metro) |
| Line 18 (Stockholm Metro) | Line 18 (Stockholm Tunnel Rail) | Line 18 (Zürich) |
| Line 18, Beijing Subway | Line 18, Chengdu Metro | Line 18, Shanghai Metro |
| Line 19 | Line 19 (Beijing Subway) | Line 19 (Chengdu Metro) |
| Line 19 (disambiguation) | Line 19 (Hangzhou Metro) | Line 19 (IndyGo) |
| Line 19 (São Paulo Metro) | Line 19 (Shanghai Metro) | Line 19 (Shenzhen Metro) |
| Line 19 (Stockholm metro) | Line 19 (Stockholm Metro) | Line 19 (Stockholm Tunnel Rail) |
| Line 19 (Wuhan Metro) | Line 19 (Zürich) | Line 19, Beijing Subway |
| Line 19, Shanghai Metro | Line 19, Wuhan Metro | Line 2 |
| Line 2 (AMTR) | Line 2 (Athens Metro) | Line 2 (Athens Suburban Railway) |
| Line 2 (Ürümqi Metro) | Line 2 (Barcelona Metro) | Line 2 (Barcelona) |
| Line 2 (Beijing Subway) | Line 2 (Berlin) | Line 2 (Bilbao metro) |
| Line 2 (Bilbao Metro) | Line 2 (Bloor-Danforth) | Line 2 (Bloor–Danforth) |
| Line 2 (BMT) | Line 2 (Brussels Metro) | Line 2 (Bucharest Metro) |
| Line 2 (Budapest Metro) | Line 2 (Busan Metro) | Line 2 (Cairo Metro) |
| Line 2 (Changchun Metro) | Line 2 (Changchun Rail Transit) | Line 2 (Changchun Subway) |
| Line 2 (Changsha Metro) | Line 2 (Changzhou Metro) | Line 2 (Charleroi Metro) |
| Line 2 (Chengdu Metro) | Line 2 (Chengdu Tram) | Line 2 (Chennai Metro) |
| Line 2 (Chongqing Rail Transit) | Line 2 (Copenhagen Metro) | Line 2 (Copenhagen) |
| Line 2 (Daegu Metro) | Line 2 (Daejeon Metro) | Line 2 (Dalian Metro) |
| Line 2 (Delhi Metro) | Line 2 (disambiguation) | Line 2 (Doha Metro) |
| Line 2 (Dongguan Rail Transit) | Line 2 (Dubai Metro) | Line 2 (Foshan Metro) |
| Line 2 (Fuzhou Metro) | Line 2 (Guadalajara) | Line 2 (Guangzhou Metro) |
| Line 2 (Guiyang Metro) | Line 2 (Hangzhou Metro) | Line 2 (Harbin Metro) |
| Line 2 (Havana Suburban Railway) | Line 2 (Hefei Metro) | Line 2 (Hohhot Metro) |
| Line 2 (Incheon Subway) | Line 2 (Incheon) | Line 2 (IndyGo) |
| Line 2 (IRT) | Line 2 (Jinan Metro) | Line 2 (Kharkiv Metro) |
| Line 2 (Kolkata Metro) | Line 2 (Kunming Metro) | Line 2 (Kunming Rail Transit) |
| Line 2 (Kyiv Metro) | Line 2 (Lanzhou Metro) | Line 2 (LanzhouMetro) |
| Line 2 (Lima Metro) | Line 2 (Lucknow Metro) | Line 2 (Luoyang Subway) |
| Line 2 (Madrid Light Metro) | Line 2 (Madrid Metro) | Line 2 (Madurai Metro) |
| Line 2 (Manila Light Rail Transit System) | Line 2 (Manila) | Line 2 (Metro Bilbao) |
| Line 2 (Metro Valencia) | Line 2 (Metrovalencia) | Line 2 (Mexico City Metro) |
| Line 2 (Mexico City) | Line 2 (Milan metro) | Line 2 (Minsk Metro) |
| Line 2 (Montreal Metro) | Line 2 (Montreal) | Line 2 (Moscow Metro) |
| Line 2 (MRT) | Line 2 (Mumbai Metro) | Line 2 (Nagoya Municipal Subway) |
| Line 2 (Nanchang Metro) | Line 2 (Nanjing Metro) | Line 2 (Nanning Metro) |
| Line 2 (Nanning Rail Transit) | Line 2 (Nantong Rail Transit) | Line 2 (Naples Metro) |
| Line 2 (Naples metro) | Line 2 (Naples) | Line 2 (New York City Subway) |
| Line 2 (New York) | Line 2 (Ningbo Rail Transit) | Line 2 (Nizhny Novgorod Metro) |
| Line 2 (O-Train) | Line 2 (Osaka Metro) | Line 2 (Osaka) |
| Line 2 (Ottawa O-Train) | Line 2 (Ottawa) | Line 2 (Panama Metro) |
| Line 2 (Paris Metro) | Line 2 (Phnom Penh Bus Rapid Transit) | Line 2 (Pune Metro) |
| Line 2 (Qingdao Metro) | Line 2 (Rio de Janeiro) | Line 2 (Rio LRT) |
| Line 2 (Saint Petersburg Metro) | Line 2 (Santiago Metro) | Line 2 (Santo Domingo Metro) |
| Line 2 (Sao Paulo Metro) | Line 2 (São Paulo Metro) | Line 2 (Seattle Sound Transit) |
| Line 2 (Seattle) | Line 2 (Seoul Metropolitan Subway) | Line 2 (Seoul Subway) |
| Line 2 (Seoul) | Line 2 (Seville metro) | Line 2 (Seville Metro) |
| Line 2 (Shanghai Metro) | Line 2 (Shaoxing Metro) | Line 2 (Shekou Line) |
| Line 2 (Shenyang Metro) | Line 2 (Shenzhen Metro) | Line 2 (Shijiazhuang Metro) |
| Line 2 (Singapore) | Line 2 (Sistema de Tren Eléctrico Urbano) | Line 2 (Sound Transit) |
| Line 2 (Surat Metro) | Line 2 (Suzhou Rail Transit) | Line 2 (Sydney light rail network) |
| Line 2 (Sydney Trains) | Line 2 (Taipei Metro) | Line 2 (Taiyuan Metro) |
| Line 2 (Tehran Metro) | Line 2 (Tehran) | Line 2 (Thessaloniki Metro) |
| Line 2 (Tianjin Metro) | Line 2 (Tokyo Metro) | Line 2 (Tokyo) |
| Line 2 (Toronto Subway) | Line 2 (Toronto) | Line 2 (TTC) |
| Line 2 (Urumqi Metro) | Line 2 (Vienna S-Bahn) | Line 2 (Vienna U-Bahn) |
| Line 2 (Warsaw Metro) | Line 2 (Wuhan Metro) | Line 2 (Wuhu Metro) |
| Line 2 (Wuhu Rail Transit) | Line 2 (Wuxi Metro) | Line 2 (Xi'an Metro) |
| Line 2 (Xiamen Metro) | Line 2 (Xuzhou Metro) | Line 2 (Yerevan Metro) |
| Line 2 (Zürich) | Line 2 (Zhengzhou Metro) | Line 2 Bloor-Danforth |
| Line 2 Bloor–Danforth | Line 2 of Saint Petersburg Metro | Line 2 of the Guadalajara light rail system |
| Line 2 of the Guadalajara urban rail system | Line 2 Orange (Montreal Métro) | Line 2 Orange (Montreal Metro) |
| Line 2 Santiago Metro | Line 2, Beijing Subway | Line 2, Changsha Metro |
| Line 2, Chengdu Metro | Line 2, Chongqing Rail Transit | Line 2, Dalian Metro |
| Line 2, Dongguan Rail Transit | Line 2, Foshan Metro | Line 2, Fuzhou Metro |
| Line 2, Guangzhou Metro | Line 2, Hangzhou Metro | Line 2, Harbin Metro |
| Line 2, Hefei Metro | Line 2, Ho Chi Minh City Metro | Line 2, Kunming Rail Transit |
| Line 2, Nanchang Metro | Line 2, Nanjing Metro | Line 2, Nanning Rail Transit |
| Line 2, Ningbo Rail Transit | Line 2, Paris Métro | Line 2, Qingdao Metro |
| Line 2, Shanghai Metro | Line 2, Shenyang Metro | Line 2, Shenzhen Metro |
| Line 2, Suzhou Rail Transit | Line 2, Taipei Metro | Line 2, Tianjin Metro |
| Line 2, Wuhan Metro | Line 2, Wuxi Metro | Line 2, Xi'an Metro |
| Line 2, Zhengzhou Metro | Line 20 | Line 20 (Beijing Subway) |
| Line 20 (São Paulo Metro) | Line 20 (Shanghai Metro) | Line 20 (Shenzhen Metro) |
| Line 20, Beijing Subway | Line 20, Shanghai Metro | Line 20, Shenzhen Metro |
| Line 201 (Calgary) | Line 202 (Calgary) | Line 203 (Calgary) |
| Line 21 | Line 21 (Guangzhou Metro) | Line 21 (IndyGo) |
