In this textbook, we describe the dynamics of vehicular traffic flow in terms of mathematical models. In the field of natural sciences, the mathematical approach has been eminently successful. Galileo Galilei is reported to have said “Mathematics is the language with which God has written the universe.” In more recent times, human decisions and actions have been described in mathematical terms as well. At first sight, this appears to be paradoxical. After all, humans and their individual decisions certainly cannot be described by a formula.