Supporting key infrastructure projects. China's armed forces bring into full play the advantages of hydroelectric, transportation, engineering and cartographic units, and support national and local infrastructure construction related to national economy and people's livelihood in such areas as transportation, water conservancy, energy and communications. Since 2011, the PLA and PAPF have contributed more than 15 million work days and over 1.2 million motor vehicles and machines, and have been involved in more than 350 major province-level (and above) projects of building airports, highways, railways and water conservancy facilities. The PAPF hydroelectric units have partaken in the construction of 115 projects concerning water conservancy, hydropower, railways and gas pipelines in Nuozhadu (Yunnan), Jinping (Sichuan) and Pangduo (Tibet). In addition, PAPF transportation units have undertaken the construction of 172 projects, including highways in the Tianshan Mountains in the Xinjiang Uygur Autonomous Region, the double-deck viaduct bridge over the Luotang River in Gansu Province and the Galungla Tunnel along the Medog Highway in the Tibet Autonomous Region, with a total length of 3,250 km.