||Human operators, with the task to control complex and dynamic systems, can be found in many different work situations. Examples are process control (nuclear power plants, industrial processes), traffic control (flight, train, road), vehicles (cars, ships, airplanes) and health care (intensive care units). The human operators normally control the system via a control system and an operator interface to this. The design of the control system and the user interface is extremely important for how the operator can perform, for quality, safety, efficiency and work environment. The situation is often made even more complex and difficult to solve when automation is a part of the control system. The seminar will describe some of the theories we base our approach to describe and analyze such work situations on, and how we design operator interfaces that support professional human operators and their skills. Examples are Situation Awareness, the GMOC model of human control, Humans and Automation, Visualization of complex information patterns and Design of operator interfaces with user centered methods. I will also describe how this has been applied in research together with Trafikverket (Swedish Transport Authority) for designing a new generation of train traffic control systems. This new principles and systems will be the basis for future traffic control in Sweden – and perhaps in Europe.