Sustainable Factor Input in Product-service Operation

Approximately 80% of the costs of Product-Service-Systems (PSS) operation are labor costs. A service company's employeesare their most important input factor, which therefore strongly defines the success of PSS operation, in particular this applies to PSS for the product usage life cycle phase. Consequently, it is very important to assign tasks to employees within a service project very much based on their abilities and the challenges of the tasks. This allows a sustainable use of the most important resource within PSS operation.The idea of human reliability is well established. Like for technical systems, the calculation of reliability is the basis for defining the error probability for a specific worker/ group of worker within a certain process step. Within PSS operation the human reliability is not only dependent on the individual capabilities but is also very much related to the serviced product. Analyzing the relevant man-machine-systems is therefore essential when reaching for sustainability in service operation.The concept of the human reliability within a PSS defines the human probability of error by the strain of a service task. The strain is dependent on the task (its processes and (technical) tool use) and the individual capabilities of the employee. The industrial psychology has identified several factors describing the stress of a task and the human abilities. Due to research within PSS operation the general idea of the relation between strain and stress can be extended to a service-strain-stress model (SSSM) which has to be seen as a qualitative framework for a classification of service employees based on the service tasks on one hand and the different individual abilities of the employee on the other hand. The SSSM allows to assign service tasks to a worker/ group of worker without exceeding a certain individual strain level and therefore to reduce the probability of error realizing a sustainable service operation.This paper outlines the idea of categorizing service operations employees according to the individual abilities, the product complexity and the time pressure within a strongly customer oriented service project. Due to the qualitative, individual characteristics of employees, the categories defined will be rather qualitative.The model can be used for a more sustainable planning of a service company's manpower or as a tool for optimizing the supply of temporary workers in the service domain. But could also work as a benchmark for service personnel management.