Improvements of some roundabout Intersections using capacity model Analysis

Abstract

Several methods of analysis have been proposed to analyze the ability of vehicles to rotate and manoeuvre during roundabout intersections. Some models have been using formulas and calculations for extracting the results manually, while other models have been used to use the engineering software for the model. Given these differences, it may not be clear how best to use them in a particular situation. When comparing methods of capacity analysis, it will be useful to know how the various techniques are performed across a set of approaches Conflicting volumes. This paper reports on the ability of techniques to rotate multiple pathways based on maximum entry and exit traffic volumes using several methods of analysis. The research study the capacity model for some roundabout intersections in Hilla city, they are, (Al- Mohafada, Al-Saia and, Sahat Abn-Idreas). The capacity equations have been examined using some of the software programs, Highway Capacity HSC 2010, (Signalized Intersection Design and Research Aid) SIDRA, (macroscopic analysis and optimization software application). Synchro 10, to reach the best solutions to describe traffic capacity for each intersection within the study area. Data have been collected according to field survey include traffic volume for different types of vehicles and pedestrians, within antemeridian & post-meridiem (a.m&p.m ) Peak Hour Volume (PHV), Number of lanes, lane width, median width, shoulder width and pedestrians crossing included too, using video technique method. Comparing the capacity for each approach and intersections using the above software programs on the bases of several variables: V/c, delay time, LOS and queue length. It was concluded that all intersections appear with the level of service LOS (E–F) according to (V/c)>1 and increase the delay time. Also, LOS improved from (F to C) when adding one lane for each approach for Al-Mohafada roundabout intersection according to output SIDRA software, as well as it was found that SIDRA software program gives significant results on a capacity model due to take into account the geometric characteristics of the intersections and pedestrian movements and crossing. Likewise, the Syncro program creates simulations of the roundabout with the traffic volumes entering the roundabout intersection, through which it identifies the conflicting points inside the circular intersection and shows the delay in each approach and also shows the queue for each approach.