Since the inauguration of the Greater Mekong Sub-region (GMS) Economic Cooperation Program in 1992, road infrastructure projects have played a very important role. Their economic significance, especially, has become a focal point after the introduction of the concept of the three economic corridors in 1998: the East-West Economic Corridor; the North-South Economic Corridor; and the Southern Economic Corridor (Figure 1). The completion of the Second International Mekong Bridge between Mukdahan, Thailand and Savannakhet, Laos was an epoch-making event in the development of the East-West Economic Corridor. The business community, however, has paid more attention to the Bangkok-Hanoi Road than the East-West Economic Corridor. This study examines the reasons why the former has received more focus than the latter, by using criteria such as population density and the economic scale at a provincial or state level. Thereafter, the effectiveness of other economic corridors is examined, by applying the same criteria.