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.