A total of 26 pilot smart cities have been selected from the ten ASEAN Member States (Table 2.1). The positive externalities arising from agglomeration can be offset by negative externalities when a city’s equilibrium size exceeds its socially optimum size (OECD, 2010a, OECD, 2015a). Traffic congestion is one of the key negative externalities of urban agglomeration, particularly in Emerging Asia. Congestion is a considerable challenge in many of the region’s cities.