Rail networks form an important part of the transport system in Australia and many other countries in the world. Railways play a vital role in its economy by transporting freight and bulk commodities between major cities and ports and by carrying passengers, particularly in urban areas. This chapter describes the general background of rail networks, limitations of current track design practices and the new developments in SMART-University of Wollongong (UOW) track design approach. It presents key parameters needed for ballasted track design, different components of track substructure, typical ballasted track problems, design criteria and traffic conditions. The chapter also describes a procedure to determine the bearing capacity of ballasted tracks. It also presents studies on the effects of confining pressure and frequency on ballast breakage and discusses the influence of ballast fouling and implications for track performance. This introduction presents an overview of the key concepts discussed in this book.