Analysis of current methods for determining saturation flows at urban controlled intersections

The process of updating regulatory documentation in the Russian Federation involves the implementation of a system of national and transitional national standards (GOST, PNST), and the phasing out of such forms of documentation as SP, ODM, etc. According to federal law, regulatory documents must not contain duplicative provisions. Currently, two standardized methodologies, based on domestic research findings and the Highway Capacity Manual standards adopted in the USA, are used to calculate saturation flow and traffic capacity at controlled intersections. These methodologies are formalized as industry road standards. The purpose of this article is to analyze the existing methodologies for calculating the saturation flow and the average delay per vehicle, as well as to compare the calculated saturation flow values from the presented documents using the example of regulated intersections. While the values of transport delays at intersections with a load factor below 1 are generally similar (calculation discrepancies are within 10%), a difference was found between the values obtained using Webster’s method and the method based on the Highway Capacity Manual when the load factor is equal to or exceeds 1. The incorrect application of these coefficients has a cumulative effect and affects the overall accuracy of calculations. Therefore, it is necessary to adopt a unified national standard for calculating saturation flow and traffic capacity, taking into account the findings of both domestic and international research.