Chongqing Rail Transit Line 3 runs from north to south, linking the districts separated by Chongqing's two main rivers, the Yangtze (Chang Jiang) and Jialing rivers. The first phase of the line began construction on 5 April 2007. The initial segment from Lianglukou to Yuanyang (18 stations, 17.5 km (10.9 mi)) opened on September 29, 2011, with a northern extension from Yuanyang to Jiangbei Airport opening on December 30, 2011 and a southern extension from Ertang to terminus Yudong on December 28, 2012. At 55.5 km (34.5 mi), Line 3 is the longest single monorail in the world by track length. Line 3 is also the world's busiest monorail line with a daily ridership of over 675,000 passengers per day.