Abstract: Ground-defects-induced road surface collapses have increasingly taken place in recent years and thus it has become a demanding need and a conundrum as well to detect the distribution and prevent disastrous impact of the defects induced mainly by unfavorable ground conditions for the safety of city road systems. By far the development of the ground defect detecting industry has been hindered due to lack of a classification system of the ground defects, relevant code(s) of practice and criteria of risk evaluation. Based upon the studies and practical applications of the studying outcomes of BGI Engineering Consultants in the last decade, applications of commonly used detecting techniques and evaluation of related risks are reviewed in this paper.