A CASE STUDY ANALYSIS OF ROUNDABOUTS ENTRY CAPACITY LOCALISED ON ONE OF THE MAIN ROAD IN SOSNOWIEC CITY (POLAND)

This paper is a case study, which among other things includes the analysis of the three roundabouts entry capacity: a turbo- and two spiralroundabouts. These intersections are located in one of the main road localised in Sosnowiec city (Poland). Before reconstruction, this road was characterised by unfavourable road and traffic conditions, insufficient capacity and low traffic safety level. The traffic congestion decreased significantly, traffic and road conditions, as well as the level of road traffic safety, were improved after the rebuilding of this route and the designing of three roundabouts on it. Results obtained from field measurements enabled comparative analysis of theoretical and empirical capacity values: lanes on the entry of turbo-roundabout and entries of the spiral-roundabout. This paper presents also characteristics of turbo- and spiralroundabouts with methods, which are dedicated to entry capacity calculation.