# Towards the Internet of Smart Trains:
## 1 Introduction  
The future of the railway industry is expected to rely upon smart transportation systems that leverage technologies over a large rail network infrastructure to reduce its life-cycle cost. New services, such as integrated security, asset management, and predictive maintenance, are expected to improve timely decision-making for issues like safety, scheduling, and system capacity. Smart railways represent a combination of interconnected technological solutions and components, as well as modern transportation infrastructure like automatic ticketing systems, digital displays, and smart meters. Likewise, these systems require seamless high data rate wireless connectivity and integrated software solutions to optimize the usage of assets, from tracks to trains, to meet the ever-growing demand for energy-efficient and safer services. The driving factors of the smart railways are expected to enforce the growth of the industry. These factors include the increasing importance of sustainability, government regulations, demographics (i.e., growing traffic of passengers and freight, aging population, and rapid urbanization), macroeconomics (i.e., limited public funding and government deficit, government initiatives and partnership models), microeconomics (i.e., price sensitivity, demands for an improved passenger experience, stakeholders interests), the growing importance of smart cities, the incredible pace of telecommunications and technological change, and the need for mobility. The global smart railway market is estimated to grow from USD10.50 bn last year to USD 20.58 bn by 2021, at a Compound Annual Growth Rate (CAGR) of 14.4% [1]. Moreover, according to the International Transport Forum of the Organisation for Economic Co-operation and Development (OECD), by 2050, passenger mobility will increase by 200-300% and freight activity by as much as 150-250% with respect to 2010 [2]. It is expected that these figures impact on each and every component of the value chain of the industry, from passenger service to the back-end organization. In addition, the complexity of high-speed railway networks has been previously studied by different research initiatives, which were primarily aimed at fostering transportation quality. Among their diverse strategic goals is the introduction of advanced communication technologies, which allows for providing improved services and for coping with the rapidly changing needs of the market [3]. Current European railway communications technology was built in the beginning of the 90 s taking into consideration well-established standards with potential to deliver the railway services at that time [4]. The inception of smart railways began with the evolution of Global System for Mobile Communications-Railways (GSM-R), which is considered to be the keystone of rail industry transformation. Rail operators mainly use GSM-R for operational voice and data communications. Over a period of time, innovation in wireless communications technologies offered reliable transmission of video and data services for long distances. In the 2000s, the introduction of novel technological solutions and various digital devices projected new application areas, such as the provision of information about the rails to passengers, the Communication-Based Trail Control (CBTC), rail traffic management systems, and Positive Train Control (PTC) solutions. However, the rail industry underwent a major revolution after 2005 with the appearance of Internet of Things (IoT) and the adoption of smart city projects, which led to the development of solutions like smart ticketing, passenger infotainment, rail analytics, and dynamic route scheduling and planning. Industrial IoT-based solutions have eventually reinforced competitive advantages and have also uncovered new business models that are already impacting the global rail industry.