This book examines the problem of interoperability related to operating rules and gives an overview of the formal method approaches related to this subject. The book examines the interoperability issues concerning implementation of European Rail Traffic Management System (ERTMS) while crossing a boarder. It also looks at the implementing of the ERTMS and provides solutions regarding operating rules for ERTMS lines, using formal methods and simulation tools. The contributors will also discuss operating rule validation and formal methods for safety assessment.