The evaluation of the capacity of signalized intersections is one of the most important parameter used in the planning, design, operation and management of urban street networks. The calculation of capacity depends on the estimation of the saturation flow of the signalized intersections. The highway Capacity Manual (HCM 2010) is used to estimate and analyze the saturation flow. This method is widely used in many countries around the world, including Syria. It reflects the local conditions in the United States of America; therefore it may not be suitable for use in our local conditions. This study includes estimation of the field saturation flow depending on the headways between the vehicles in the queues, and comparing the field results of the saturation flow with the values resulting from using the HCM. The study was conducted on three intersections in the Tartous city. The analysis was based on data collection using video. The final results confirmed that there is a clear difference between the field measurement of the saturation flow and computation value, Which confirms that it cannot be used for our local conditions.