This work provides a systematic and comprehensible introduction to modern tunnel construction. It takes into account design elements and equipment for both road and railway tunnels. Furthermore, it includes the fundamentals of rock mechanics and specifically addresses the statistical and other mechanical issues related to tunnel construction. Older, more intuitive concepts are contrasted with a purely rational approach. A variety of new approximate formulas allow for quick preliminary sizing and estimation of relevant parameters. The use of these formulas is illustrated with examples from completed tunnel construction projects.