# The Role of Maintenance Operator in Industrial Manufacturing Systems: Research Topics and Trends
## 6 Research Agenda  
Review results underlined that the performance of maintenance operator depends on numerous individuals, environmental and organizational factors. It is essential to know and manage these aspects because they have impacts on both the single maintenance task and the overall system. Figure 10 shows the conceptual framework achieved through the analysis of the selected papers. The framework underlines the research agenda in the investigated field and the identified research trends, shedding light on several research opportunities. The research field analyzed in this paper is highly heterogeneous and varied, as evidenced by the topics identified through the LDA approach. Furthermore, several gaps have been found in current literature, which then represents future research opportunities (_ROs_). _Research Opportunity 1 (RO1):_ First of all, despite several HRA models and their applications, there are no approaches developed with the specific purpose of assessing the maintenance operator's reliability. Several efforts have been made and are still ongoing in the high-risk industries, like NPP or aviation, in order to understand the main error contributing factors and to develop methodologies for the assessment and reduction of human error in maintenance, as underlined by Reference [8], but the same is not true for other industrial sectors, as particularly manufacturing, where there is a need to be filled. A first step in this direction was proposed by Reference [36], where a taxonomy of PSF for the specific maintenance field was proposed. Furthermore, as underlined in the results section, trends 1 and 2 showed several links. Many of the decision and management models developed in the papers belonging to the trend 2 exploited the HRA methodologies and approaches, which characterize the first trend. However, there are few relations with the third trend. No paper exhibits both topic on enabling technologies and human reliability or factors influencing maintenance performance with the introduction of new technologies. The quantification of human reliability during a maintenance activity supported by the new technologies is an uncommon issue not discussed in the literature. In current literature, indeed, the study of maintenance operator reliability supported by new technologies as well as the identification, analysis, and classification of new PSFs that affect performance are missing. For these reasons, new HRA methods ad-hoc for evaluating maintenance processes, and including all the impacting factors (trend \(1+2+3\)), should be proposed. The verticalization of the HRA methods on maintenance activities will allow us to evaluate for the specific maintenance tasks the performance of the operators and the main impacting factors, and therefore to identify the main causes of problems, in order to mitigate and  
Figure 9: Topics grouped into the research trends identified. reduce these errors and improve the health and safety of the operators, as well as the performance of the system. _Research Opportunity 2 (RO2):_ This need becomes increasingly evident when one considers the evolution taking place in manufacturing systems. The Industry 4.0 paradigm is transforming the concept of traditional production systems into the widespread model of smart manufacturing, however, is not just about technology, it is also a new cultural paradigm with an impact on the workforce at all levels and for all business functions. The Industry 4.0 paradigm is changing the roles and job requirements of employees, influencing the workers and the nature of their work, and creating new interactions, not only between humans and machines but also between the digital and physical worlds. While significant attention has been given to the technologies for the past decade, the human element is still important [96]. This led to the spread of the new term of operator 4.0 as a relatively new term [97; 98], which evolved from an analogy of the industrial revolution concept mentioned earlier.