Preface

The rapid expansion of transportation industries worldwide, including railways, and the never-ending desire to reduce travel time have highlighted the need to resort to advanced transit systems. Conventional railway systems have been modified to make travel at much higher speeds possible. *High-Speed Rail* includes the main topics and basic principles of high-speed railways (HSR). The book reflects new engineering and track developments, the most current design methods, as well as the latest industry standards and policies. This book provides a comprehensive overview of the significant characteristics for HSR, highlighting recent advancements, requirements, and improvements, and details of the latest techniques in the global market. *High-Speed Rail* contains a collection of the latest research developments on HSR, comprehensively covering basic theory and practice in sufficient depth to provide a solid grounding for railway engineers. The book will also help readers to maximize effectiveness in all facets of HSR. It is a professional book and a credible source and valuable reference that will be applicable and useful for all professors, researchers, engineers, practicing professionals, trainee practitioners, students, and others interested in HSR. The book consists of four chapters.

Chapter 1 reviews HSR. HSR is defined as an intercity passenger transit system that is time competitive with aircraft and/or automobiles on a door-to-door basis. The fundamental reason for considering the implementation of rapid transit systems is higher speed, which can easily equate to shorter travel time. Therefore, there is a need to look at the technical specifications of each technology by examining the potential improvement of each technology in terms of speed, travel time, and other advantages. People have always demanded reductions in travel time for many good reasons, such as trade, leisure, etc. This has forced the rapid expansion of transportation industries worldwide, including railways. Consequently, high-speed transit systems have been introduced in many countries. These systems are manufactured based on advanced engineering methods and technologies. The congestion in transportation modes associated with increased travel has caused many problems, including public concerns, among which are prolonged travel time, growing accident rates, worsening environmental pollution, and accelerating energy consumption. On the contrary, high-speed ground transportation, characterized by high speed, operating reliability, passenger ride comfort, and an excellent safety record, is considered one of the most promising solutions to alleviate congestion.

Chapter 2 includes an overview of the different elements present in the railway superstructure of high-speed lines in Spain. The performance of rail transport has increased significantly in recent decades, in particular due to the gradual introduction of HSR worldwide. In 1981, the world's first high-speed line was inaugurated (Paris–Lyon, 425 km); nowadays, high-speed networks are in operation in more than 20 countries covering more than 35,000 km (with more than 25,000 additional km under construction). Spain is one of the leading countries implementing high-speed rail. In fact, Spain is the second country by total distance of railways installed (only behind China) and the first relative to population and surface. Since the installation of the first high-speed line in Spain in 1992, the elements of the superstructure (sleepers and fastening system) have undergone a continuous

evolution to improve performance, ensure durability of the components, and maximize the comfort of passengers. This evolution is due to an adequate selection of materials based on the characterization of their physical and mechanical properties to ensure optimum in-service conditions. Throughout this chapter, the innovations that have been incorporated over time are analyzed, as well as the methods used to validate them. In particular, a description of the mechanical characterization procedures is presented.

 Chapter 3 evaluates contemporary inspection and monitoring for high-speed rail systems. Non-destructive testing (NDT) techniques have been explored and extensively utilized to help maintain safe operation and improve ride comfort of the rail system. In line with the ascension of NDT techniques, structural health monitoring (SHM) brings a new era of real-time condition assessment to rail systems without interrupting train services, which is significant to HSR. This chapter first gives a review of the NDT techniques for wheels and rails, followed by recent applications of SHM on HSR enabled by a combination of advanced sensing technologies using optical fiber, piezoelectric, and other smart sensors for onboard and online monitoring of railway systems from vehicles to rail infrastructure. An introduction to the research frontier and development direction of SHM on HSR is also provided and concerns both sensing accuracy and efficiency through cutting-edge datadriven analysis studies embracing wireless sensing and compressive sensing, which endorse big data's role in this new age of transport.

Chapter 4 considers the methods to increase the performance and reliability of reprofile machining of wheel tread profiles. Looking beyond both milling and turning, the cutting tool is the key element to ensure performance and reliability of the manufacturing process, and the study considers methods to increase the performance properties of cutting tools. In particular, the study includes the investigation of ways to improve cutting tools (carbide inserts) to machine wheel tread profiles.

> **Dr. Hamid Yaghoubi**  Director of Iran Maglev Technology, Iran
