This article presents basic issues related to operator workload assessment in the context of man–machine–media system (3M) improvement. Organizations that want to operate safely need effective tools to monitor and identify hazards in a safety system. Some prov-en solutions to that have been used for some time in aviation. Two elements of the 3M system are monitored at a good level (machine and media), but the human element is monitored using mostly subjective methods. According to research, the human factor is the most common cause of adverse events and is the most important, but its monitoring is not sufficient. The main aim of the paper is finding a solution to this problem by introducing the concept of operator workload assessment used in aviation. It consists of three types of monitoring, which emphasizes objective data acquisition, with a system based on objective methods of measuring the response of the human body to workload changes. It is meas-ured according to the adopted scheme for methods of data analysis from flight data re-corders or from ground-based recording devices. This group includes a number of methods that record changes in one or several physiological parameters. In addition, there is infor-mation about the types of safety strategies, the idea of levels of human reliability and the relationship between workload and performance.