Megacities in developing countries suffer from serious traffic congestion, high levels of greenhouse gas (GHG) emissions, and heavy air pollution. These urban areas face a stark dilemma: economic expansion attracts more people and vehicles; but the resulting traffic and pollution hinder further growth while reducing the quality of life for their citizens. Today, Seoul boasts a passenger-trip share for metro and bus of more than 60 percent. Energy consumption in Korea’s road sector is lower than in other countries with similar gross domestic product (GDP). Congestion costs have been decreasing, and carbon dioxide (CO2) emissions in the transport sector have been kept under control.