Abstract: Abstact: China is meeting the grand challenge while facing many problems brought by the rapid urbanization in the past decades. As a result, effective policies are called for to assure the sustainability of urban spatial development. Modeling urban spatial development process for policy test would be of great significance for decision making and the eventual realization of sustainable urbanization. The objective of this paper is to establish an operative model to simulate urban spatial evolution process that would help to formulate urban spatial policies. Land-use/transport interaction model (LUTI) is considered an important tool to model urban spatial development processes. We think that urban land use reflects the spatial distribution of urban economic and social activities, and urban expension and land use changes reflect the changes of urban activity distribution caused by the interaction between land use and transport. Using the LUTI concept and taking economic and social activities as an enentry point, we built an urban activity spatial evolution model (UASEM) and discussed the implementation of this model in details. UASEM includes a number of submodels, including an Activity Transition Model that predicts the amount of activities, an Estate Development Model that predicts the floorspace of buildings, a Transport Model that evaluates transport accessibility, and an Activity Location Model that predicts the spatial distribution of socioeconomic activities. The paper introduces the implementation of each submodel of the UASEM and maps the relationship between them, so the UASEM given in this paper is an operative model. UASEM is a computer model that includes an itarative programe, which simulates the iterative process of urban land use and transport interaction. To ensure that the model results converge, boundary condition of the model is carefully examined. UASEM is a dynamic model that takes into account the change of every activity. The spatial and tempral dimensions of UASEM need to be decided according to the urban scale and data availability. Towns are normally the basic spatial unit of analysis and the temporal scale of such analysis is often annual. UASEM results provide a reference for researches of urban modeling and analysis in China.

Key words: accessibility, land use/transport interaction model (LUTI), simulation, urban space