Novel mathematical modelling approaches and a new lower bounding scheme for multi-manned assembly line balancing problems with walking workers

•Two novel mathematical modelling approaches and a lower bound calculation method are suggested for MMALBP-WW.•The performances of all models are compared with each other using benchmark test instances.•One of novel modelling approaches exhibits superior results than the existing one in all aspects.•The advantages of the proposed lower bounding scheme have been demonstrated. This article suggests two novel mathematical modelling approaches and a lower bound calculation method for the number of workstations to balance multi-manned assembly lines with walking workers. While new formulations include more variables, they require fewer constraints than the existing one. The performances of all formulations are compared each other using benchmark test instances from the literature as well as the instances produced in this study. Comparison results showed that one of novel modelling approaches exhibits superior performance than the existing one in all aspects. It has been demonstrated that the proposed model can be applied to practical-sized instances of the problem. Also, the advantages of the proposed lower bounding scheme have been shown.