Due to global completion in the automotive industry, productivity improvement is vital in these industries. In automotive assembly lines, productivity loses are attributed to bottlenecks, long processing time in workstations and underutilization of resources. The purpose of this research is to evaluate the performance of the production system, analyze the bottlenecks in different parts of the workstation, their capacity and constraints. Also, develop different scenarios for improvement. To achieve this objective, a simulation model was developed using Arena Software to analyze bottlenecks in each workstation. The analysis was based on the queue in the system to identify the longest queue in workstations. After analysis of the assembly line, the result showed that the longest waiting time observed is cab preparation and drop, bumper, engine subassembly fitment of soundproof with respective numbers 14.4, 13.97, 13.00, 13.70 minutes, with respective average number waiting of 24.87%, 17.57%, 25.91% and 23.39%. Using different scenarios for the improvement of the production line showed that the waiting time observed in-cab preparation and drop, bumper, engine subassembly, fitment of soundproof has greatly reduced for the two workstations added and three operators respectively from 14.4 to 3.97 and 3.1, from 13.97 to 3.77 and 2.48, from 13.00 to 4.21 and 3.83, from 13.70 to 0.00 and 2.37 minutes, with respective average number waiting from 24.87% to 5% and 2%, from 17.57% to 5% and 0.9%, from 25.91% to 5% and 4%, and from 23.39% to 0.00% and 3%. To conclude the research study was able to demonstrate the modelling approach using simulation for analysis of a production line assembly. The contribution of this research was so enormous, this study has improved the output production up to 144%.