A Comparison of the Saturation Flow Rates Obtained From Field Observations and Highway Capacity Guides for the Signalized Intersections in Iran and To Identify the Most Appropriate Guides

The saturation flow is one of the essential parameters for analysis and design of signalized intersections. The value of this parameter is affected by traffic behavior and other conditions in each country. On this basis, different values and methods are proposed in the highway capacity guides of different countries. There have been limited researches to estimate this parameter under Iranian traffic conditions. In this study, field measurements of saturation flow for14 entry approaches related to the signalized intersections, located in the city of Yazd in Iran, were conducted and then compared with their corresponding values estimated from Highways Capacity Guides of  United States, Canada, Australia, Malaysia, Indonesia and Iran. The results indicated that for the protected-left turn movements, Australian Guide and in a close competition, Iranian Guide outperformed other guides. For the un-protected left turn movements, American Guide outperformed other Guides. The results indicated that the current Iranian Guide is not appropriate the un-protected left-turn conditions and further researches and developments in this area are needed.