This book discusses the critical issues in selecting conventional and mechanized tunneling methods and lessons learned from the past. It covers the following main topics: geological and geotechnical parameters affecting tunneling methods, summarizing conventional tunneling and mechanized tunneling methods, the factors affecting the choice of tunneling methods such as the cost of the initial investment, the length of the tunnel,   project scheduling,   time for mobilization, emerging new technologies. Some examples of changing the tunneling method from conventional to mechanized tunneling or vice versa during the same ongoing project and hybrid tunneling methods in the same project are also given. The last chapter resumes the innovations made for the tunneling industry, summarizing advancements in safety, non-circular TBMs, robotics, new instrumentation, new materials and methodologies to decrease carbon footprint. This book is aimed at graduate students, professionals and researchers in tunneling, civil and mining engineering and geology.