The Bangkok Metropolitan area has a population of approximately 9.79 million people (as of 2005) and is the political and economic center of Thailand. With Thailand's economic recovery following the Asian currency crisis, urban industrial activity has surged, leading to an increase in the number of automobiles and other vehicles. As a result, there has been a serious rise in traffic congestion in the transportation system, which depends heavily on the automobile. Moreover, air pollution caused by automobiles is recognized as a problem, and measures to ease the load on the environment are required. The aim of this project is to increase in traffic demand and mitigate traffic congestion in Bangkok Metropolitan Area by constructing new mass transit railway line, thereby contributing to urban economic development and environmental improvement.