The bicycle production company Accell-group N.V. aims to improve their bicycle assembly lines. The assembly of bicycles requires fastening a large amount of parts using a variety of fastening techniques. In the investigated situation, these assembly operations are performed on an assembly line. The goal of this thesis is to structurally improve assembly lines on assembly time, product quality, assembly costs, assembler workload and number of faulty bicycles. To achieve these goals, a 7 step method is developed to find the largest improvement opportunities of an assembly line, determine which movements of the improvement opportunities are sub-optimal, determine what the root causes of the sub-optimal movements are and to ideate solutions to eliminate these root causes. This minimizes sub-optimal movements during assembly. The developed method was tested by applying it to three assembly line operations, which resulted in a reduction of assembly time and improvements towards the stated goals in all three tested situations. The outcomes of the thesis are an overview of the most promising improvement opportunities of the investigated assembly line, the developed method and practically tested improvement suggestions for the investigated assembly line.