This report of the Transportation Research Board (TRB) presents data obtained from a review of the literature and a survey of North American and international transit agencies. In addition, five case studies are presented to look more closely at the tunnel inspection practices of four domestic and one foreign transit agency. The Appendix material includes examples of the inspection forms used by the five agencies profiled. To develop this synthesis in a comprehensive manner and to ensure inclusion of significant knowledge, available information was assembled from numerous sources, including a number of public transportation agencies. A topic panel of experts in the subject area was established to guide the researchers in organizing and evaluating the collected data, and to review the final synthesis report. This synthesis is an immediately useful document that records practices that were acceptable within the limitations of the knowledge available at the time of its preparation. As the processes of advancement continue, new knowledge can be expected to be added to that now at hand. (Author/publisher).
Abstract