1.Introduction to Planning Before planning the use of the subsurface,we should keep following principal questions in mind: 1)What are the advantages of using underground space based on? 2)Who benefit from the advantages of using underground space? 3)What factors are to be taken into account to assess the advantages? 4)What is the distinction between direct and indirect advantages? 5)How to value the advantages? 百年同桥 TONGILUNIVERSITY 10 Before planning the use of the subsurface, we should keep following principal questions in mind: 1）What are the advantages of using underground space based on? 2）Who benefit from the advantages of using underground space? 3） What factors are to be taken into account to assess the advantages? 4） What is the distinction between direct and indirect advantages? 5）How to value the advantages? 1. Introduction to Planning