General aspects of Human Machine Interface (HMI) are very hard to be defined. They are the on the top level of interest when studying the reliability of the human operators. The first part of our article deals with general problems of HMI and its application on the tasks of the transportation. In the second part it is discussed the abstraction and definition of human operator operating artificial transportation means. Our research is mainly focused on the reliability of the interaction processes between the driver and vehicles, pilots and aircrafts (i.e. cars, trains etc.) so the final paragraphs deals with concrete examples of a usage of our methodology which we apply on experimentations on vehicle simulators. The final part deals with the main result, the methodology for classification of User Interfaces (UI) suitability (continuously developed in our laboratory), which is based on measurements of technical and biological signals (like EEG, ECG etc.) considered as the output from the complex system of interaction between a human and an artificial system.