4. Results 4.1. Response and retention rateThe questionnaire approach is used in this research to collectdata from the main participants in 5 cities on different metroconstruction projects, including clients, consultants, designers,contractors and supervisors. 120 questionnaires were distributed,and a total of 104 usable questionnaires were collected, resultingin an 86.7% response rate for the survey. The remaining 13.3% indi-cated they did not have enough time to complete the survey orthey were not interested. Table 2 shows the distribution of usablequestionnaires.