Connecting to National Freeway Number Three at the Nangang System Interchange, the Nangang - Suao section of National Expressway Number Five passes through Shihding and Pinglin in Taipei County, the Hsuehshan Tunnel, and then enters Yilan County, passing through Toucheng, Jiaosi, Jhuangwei, Yilan, Wujie, Luodong, and Dongshan, before ending in Suao. The total length of the Expressway is 55 kilometers. It is the first national expressway linking eastern and western Taiwan. To commemorate its completion and its opening to traffic, Chunghwa Post is issuing a miniature sheet entitled "Completion of the Nangang - Suao Section of National Expressway Number Five Commemorative Miniature Sheet" with denomination of NT$12.00.   The Nangang - Suao section of National Expressway Number Five runs through mountainous areas and river valleys. In order to protect the natural scenery along the way, tunnels and viaducts, which have little impact on the environment, were adopted for most stretches of the route. In this way, the expressway builders reduced the amount of excavation and avoided construction that would seriously add to water pollution. The expressway is a model of ecological and environmental protection. The 12.9 km Hsuehshan Tunnel, the fifth longest tunnel in the world and longest in Southeast Asia, was the most challenging part of construction. With completion, travel between Taipei and Yilan has been significantly reduced to 30 minutes from two hours. The expressway greatly promotes the prosperity of local industry and helps to balance economic development between eastern and western Taiwan.