Many traffic control tools such as Variable Speed Limits (VSL), Ramp Metering, etc are applied to improve freeway traffic flow and through these tools various undesirable phenomena like shock waves and queues on traffic flow can be eliminated or reduced. The aim of this study is to analyze a 2.5 km section of O1 Freeway in Istanbul and to model it analytically with a macroscopic analytical traffic flow model METANET. The section under consideration has two merges. Traffic congestion, shock waves and queues occur on the section in rush hours. The fundamental parameters of METANET were estimated by using MATLAB. Data needed (speed and density) to estimate METANET parameters were collected from CORSIM simulation software calibrated for this section. The calibrated METANET model was able to represent traffic flow on the section successfully. It is expected that the calibrated METANET model can be used for performing studies on traffic control for a forecasting model.