Hardware-in-the-loop simulations for railway research

EDITORIAL: Hardware-in-the-loop simulation (HILS) is one of the high-tech approaches that combines theory, numerical simulation, software, digital communications, data acquisition, instrumentation and control to give a mechatronic system. Such a system can be utilised to simplify development and design processes for complex systems as well as their testing and validation, which allows reduction or, in some cases, avoidance of the high cost of real field tests. It is well known that the automotive industry has implemented HILS widely in their research projects and investigations, but what is a situation with HILS in railway research?