Design recommendations for the acceleration lane length are based on research and monitoring data made decades ago and have recently been the subject of discussions and innovations. Designing a highway acceleration lane differs between urban and non-urban areas by a large number of parameters. Specificities of urban space, multimodal demands of traffic users, environmental requirements and inherited spatial relationships make optimization of the acceleration lane length a real challenge. The development of analytical, analytical-empirical and simulation methods for evaluating design solutions is generated by the desire to make the analyses performed in the planning phase as realistic as possible. Microsimulation traffic tools, such as VISSIM, enable the analysis of variant solutions and the optimization of road design elements for existing as well as for future traffic demands. This paper presents an analysis of two existing acceleration lanes on the southern bypass of the city of Osijek. Microsimulation results show that there is a potential for shortening the length of acceleration lanes in the current traffic demand conditions. Various scenarios of the increase in traffic of the main and secondary traffic flows have been analyzed. The results were evaluated through the criteria of selected functional indicators, which are average delays and queue lengths. This research contributes to the methodology of applying modern simulation tools in the analysis and optimization of traffic infrastructure elements in local conditions.