Assembly lines are flow-line production systems which are of great importance in the industrial production of high quantity standardized commodities and more recently even gained importance in low volume production of customized products. Due to high capital requirements when installing or redesigning a line, configuration planning is of great relevance for practitioners. Accordingly, this attracted the attention of research, who tried to support practical configuration planning by suited optimization models. In spite of the great amount of extensions of basic assembly line balancing there remains a gap between requirements of real configuration problems and the status of research. This gap might result from research papers focusing on just a single or only a few practical extensions at a time. Real-world assembly systems require a lot of these extensions to be considered simultaneously. This paper structures the vast field of assembly line balancing according to characteristic practical settings and highlights relevant model extensions which are required to reflect real world problems. By doing so, open research challenges are identified and the practitioner is provided with hints on how to single out suited balancing procedures for his type of assembly system.
