# The Role of Maintenance Operator in Industrial Manufacturing Systems: Research Topics and Trends
## 4 Paper Content Analysis  
### Topic 1 and Topic 2: Human Error and Human Reliability in Industrial Maintenance  
Topic 1 covered papers dealing with human error in industrial maintenance, while Topic 2 included papers dealing with the analysis of Human Factors (HF) and Human Reliability (HR). HR can be defined as the probability of humans performing specific tasks with satisfactory performance. Several methods and approaches were proposed in the literature for measuring human error and predicting human reliability during working activities. HRA aims to quantify the likelihood of human error for a given task, supports operations managers and provides guidance on how to improve reliability for that task. Figure 6 presents the distribution trend over the years of the papers belonging to Topic 1 and 2 [8; 9; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37] with respect to the total selected papers. These topics have been extensively covered over the years, particularly in 2013, 2014, 2015, and 2016. Figure 6: Distribution of the papers belonging to Topic 1 and Topic 2 over the years with respect to the total number of papers. Topic 1 includes several types of contributions (literature reviews, HRA models, frameworks, and case studies). A systematic literature review on human error in industrial maintenance was conducted in Reference [8], which provides state of the art human error in maintenance, underlining several topics: methodologies for human error analysis and integration in maintenance management; error contributing factors; and maintenance error consequences. Several features of human error in maintenance, essential for improving the factories of the future, are discussed by Reference [20]. The authors provide insights into the occurrence of maintenance errors in the equipment life cycle, the causes for the maintenance error's occurrence, as well as types and typical maintenance errors, common maintainability design errors, useful design guidelines to reduce equipment maintenance errors, and maintenance error analysis methods. Several methods for HR analysis were found in the current literature. Some were based on the risk probability assessment, such as Reference [22], which proposed a risk model for the definition of the function of reliability (or failure) of \"human component\" in a railway system and Reference [26], which presented a risk-based methodology to estimate shutdown inspection and the maintenance interval by integrating human errors with degradation modelling of a processing unit. Some of the papers [17; 19; 28; 34] adopted the HRA methods, analysed maintenance error, and measured the occurrence of human error during maintenance tasks. For example, Reference [17] presents a conceptual modelling of human error, defined the system failure, listed and analysed the related human operation, estimated the error probabilities and the effects of human errors on the system. Two types of errors are considered: Error of Omission (EOO) and Error of Commission (EOC); the Swiss cheese model is used to conceptually model the problem; for the estimation of human error probabilities, the Technique for human error-rate prediction (THERP) is adopted and two cases are taken into account: in one case, the maintenance task is performed with supervision, whereas in another one without supervision. In the study proposed by [PERSON] [19], pre and post maintenance activities of a condenser pump was investigated in order to understand the role of human error, using the Human Error Assessment and Reduction Technique (HEART). The identification of activities with high HEPs allowed us to suggest mitigation measures to reduce errors and consequently move towards lower probabilities of poor performance. The aim of the paper [28] was to validate the consistency of the three HRA methods (HEART, SPAR-H, and Bayesian Network (BN)), through a case study of a cable manufacturing company.