This paper deals with the design of a safety-critical embedded system for railroad vehicles usually referred to as "dead-man's vigilance device" (DMVD). A DMVD monitors the activity of the operator driving a train to detect his/her possible incapacitation while the vehicle is traveling. The system relies on a redundant and diverse FPGA-based architecture (without using micro-controllers, soft-cores or other software programmable components) to assure good flexibility and to avoid complex and expensive validation and verification activities of software modules, as typically required in safety-oriented applications. The first tests conducted on a prototype confirm that the system behaves correctly both in normal operating conditions and in the presence of single faults.