Abstract: To effectively utilize existing underground space resources and facilitate the implementation of urban renewal action, herein, a decision treebased planning assessment method for the renewal and transformation modes of aged urban underground space projects is proposed. Furthermore, based on the case studies of exemplary aged underground space projects around the world, the renewal and transformation modes of such space projects are divided into seven principal categories (underground dynamic transportation, municipal utility, storage and logistics, commerce, entertainment, community service, and static transportation) and 21 subcategories. A characteristic index system for factors influencing the renewal and transformation modes is established, which includes land type, structure form, area, buried depth, and surrounding location conditions. Additionally, a sample set comprising 24 basic samples and 1 605 constructed samples is built for the decision tree of aged underground space project renewal. According to the characteristics of aged urban underground space projects, a strong correspondence principle of "principal categoriessubcategories" is proposed in the decision tree method along with a suitable reliability evaluation and quadratic decision method for the decision tree. Results of the model assessment indicate that the prediction accuracy of the proposed method can guarantee a reliable decisionmaking process. A case study of the Zhongshan road area, Qingdao, shows strong feasibility of the proposed theoretical method.

Key words: urban underground space, aged underground space projects, renewal and transformation modes, decision tree, planning assessment method