Transportation issues in developing China's urban agglomerations

With the rapid development of economy and society, the urbanization process is speeding up in China. Thereupon, several large-size urban agglomerations (or city groups) have emerged. In the present China, a typical city group consists of more than three cities, which are 50-250 km apart from each other, closedly connected in social and economic activities but administratively belonging to different provinces, and each has a population of over five million. It has become an enormous challenge to develop a comprehensive modern transportation system to serve the intercity and intracity traffic effectively, smoothly and eco-friendly. This article presents representative research progress in developing and operating such systems, with consideration of the state condition in China. The following topics, but not limited to, are addressed: (1) Travel behavior analysis and demand integration management within a city group; (2) Agglomeration system design and operation management; (3) Risk identification and emergency management of the agglomeration system; (4) Sustainable development issues.