As of 2017[update], four metro lines, the 14 km (8.7 mi) long CRT Line 1, a conventional subway, and the 19 km (12 mi) long heavy monorail CRT Line 2 (through Phase II), Line 3, a heavy monorail connects the airport and the southern part of downtown.,[119] Line 6, runs between Beibei, a commuter city in the city's far north to downtown.[120] Line 5 opened in late 2017.