The book first published about two decades ago covered the essential aspects of tunnels in general and Transportation Tunnels in particular. It has been now throughly revised to reflect the advancements in the basic knowledge of ground behaviour and changes in technology and construction methodology. Two new chapters one on instrumentation and the other on Inspection and Maintenance of Tunnels have been added. A number of case studies have been included to illustrate problems met with in planning, design and construction of tunnels. As presented now, the book covers essential aspects of survey, investigations, including instrumentation, design, construction, inspection and maintenance of tunnels. Need of ventilation and lighting of Railway and Highway tunnels have been covered adequately. The authors have drawn information and data from a number of previous publications, codes, reports and departmental web sites to make them detailed and authentic.