The article is devoted to the study of diagnostic methods used in the dynamic operation of road construction machines. It describes existing methods that can further be used to create an expert diagnostics system. The intelligent systems’ diagnostic methods (mainly non-destructive testing methods) considered in the article can improve the accuracy of diagnosing and predicting the metalwork condition. The service life of metalwork depends on many factors, such as force impacts, load dynamics, environmental corrosive power, high temperature effects, etc. It is possible to extend the service life of products by increasing the accuracy and timeliness of diagnosis. The article discusses the expert system architecture visually showing the relationship between the subsystem and dynamically changing system properties. The proposed architecture allows for the most comprehensive analysis of complex technical systems’ behavior, as well as for the prompt expert decisions. An integrated approach is suggested in the operation of expert systems where preference is given to theoretical, most often mathematical methods that are more generalized and less related to the subject area. Also, the author introduced a mathematical model that reflects the logic of the expert system decisions.