with the rapid trend of urbanization process, building sustainable new towns to alleviate the " megapolis disease " is the main planning means in the process of urban development in many countries. As the construction of regional express rail transit(RER) has an important impact on urban development and the construction of new towns, how to establish a mutually reinforcing relationship between RER and urban development has aroused widespread concern. In this study, a combination of literature review and case study was used to explore the impact of RER on urban development. This study makes a historical review of the development of RER in Paris and the planning and construction of surrounding new towns. The paper discusses the relationship between RER and the evolution of population structure and employment, as well as the layout of land and land, which has reference significance for other new towns construction and RER development.

CICTP