One of the main goals when operating the assembly line is to reach maximum productivity with given resources. Many previous studies have addressed worker assignment and balancing problems for various assembly lines. In this study, we consider the automotive parts assembly line where multiple workers can simultaneously perform tasks on the same product and the processing time of each task vary by the worker. Also, to secure each worker’s working space, two positional constraints are further considered. We develop a branch-and-bound algorithm to obtain an optimal solution for small-sized instances and a heuristic algorithm for large-sized instances.