This book reports on cutting-edge theories and methods for analyzing complex systems, such as transportation and communication networks, discussing multi-disciplinary approaches to dependability problems encountered when dealing with complex systems in practice. It presents the most relevant findings discussed at the 25th International Multidisciplinary Conference on Reliability and Statistics in Transportation and Communication (RelStat 2025), which took place on October 16-18, 2025, in Riga, Latvia. The chapters span a broad spectrum of advanced theories and methods, at the intersection between reliability, statistics, digital technologies, and smart mobility. They cover topics in smart and sustainable transport systems, green logistics and resilient systems, urban safety, human-machine collaboration, and AI applications in education.  All in all, this book offers extensive information to academics, practitioners, and policymakers engaged in shaping the future of transport and communication systems in the digital era.