Characteristics and classification of the annualised working hours planning problems

Annualising working hours (i.e., the possibility of irregularly distributing throughout the year the total amount of the employees working hours) is one of the means to face the seasonal nature of the demand. Annualising working hours provides much flexibility to the production system (which is one of the main principles of lean production), so the company is allowed to plan the staff working time more efficiently. However, doing irregular working weeks implies a worsening of the working conditions that could be compensated by reducing the workers annual working time. On the other hand, conditions are provided in order to avoid an excessive workers’ overburden in long periods of strong demand. This paper introduces annualised hours (AH) as a mean to achieve production flexibility and proposes a classification scheme of the annualised working hours planning problems that arise in services and in manufacturing, as well as an approach for solving them by using mixed and integer linear programming and assessing the benefits of introducing AH.