This paper describes the results of the critical headways surveys at roundabouts in the Russian Federation. The project is finished in 2017 and its main target is to improve the capacity and delays estimation technique. In the period of the USSR the manual of traffic circles and roundabouts design was prepared in the middle of the 80th of last century. The former manual contained the capacity estimation technique considering conflict points and weaving zones. In 40 years have changed a lot of things: daily volumes, structure of traffic flows, cars and tracks dynamic, as well as drivers behavior. The results of current project allowing to consider the actual traffic conditions at roundabouts in Russia and feature of driver’s behavior.
During processing of the obtained data there was a problem of the choice of the critical headways estimation technique. During the observation we got a lack of saturated conditions which are continuous queuing on the minor road entering the roundabout. So Siegloch’s method which requires saturated conditions has been rejected and Ruff's method was chosen. Raff’s method is based on simple technique of the accepted and rejected intervals consideration and no iterative procedures are required. Received results confirm that the general equations of roundabout’s capacity estimation (HCM 2000 and HCM 2010) are applicable in Russia.

roundabouts, gaps assumption, critical gaps estimation