Abstract
In the present-day, congestion considers one of the biggest problems experienced by urban areas. This congestion led to form the conflicting movements at intersections, merging, roundabouts, etc. The objective of this study is to investigate the traffic congestion problem at the two selected roundabouts at CBD area in Hilla city. Roundabouts consider safer than the conventional intersections, but it has less capacity than corresponding intersections. In Iraq, several roundabouts were built in the last decade to improve the traffic performance. However, most of these roundabouts are unable to accommodate the rapid growth in traffic volumes and suffer from a serious issue in congestion. Therefore, this study aims to evaluate these roundabouts. The VISSIM simulation software has been used to perform the evaluation analysis for these selected roundabouts. Then, field data have been collected by using two video cameras that installed by using a fabricated equipment. The process of collecting data has lasted for 8 hours at each roundabout. And then, this field data has been used to calibrate the simulation model (VISSIM). After making the required calibration and validation for the simulation model, the developed model was depended to perform the evaluation and find the suitable solution to solve the traffic congestion at these roundabouts.
Highlights
There are many of studies around the world confirm that those roundabouts are safer and more efficient than traditional intersections and they are widely used in urban areas and on high-speed roads throughout the U.S and India
The main points that have been concluded from this study are: 1. According to field data, the capacities of the selected roundabouts are so limited due to the high traffic movements at these locations especially at peak hour periods
Simulation model represents the best solution to model the behavior of roundabout characteristics
Summary
There are many of studies around the world confirm that those roundabouts are safer and more efficient than traditional intersections and they are widely used in urban areas and on high-speed roads throughout the U.S and India. Rahmi [7] pointed out that when roundabouts operate at capacity, they offer lower vehicle delays than at other intersection forms It is unnecessary for traffic at a roundabout to come to a complete stop when there are no conflicts. The gap-acceptance model is developed based on the mechanism of accepting and rejecting gaps in the major stream (circulating traffic) by drivers on the minor stream depending on critical headway and follow-up time such as the Australian SIDRA intersection model and the HCM 2010. Microscopic models treat each vehicle, pedestrian, etc., as a unique entity with its own goals and behavioral characteristics, each possessing the ability to interact with other entities in the model These models capture the interactions of real world road traffic through a series of complex algorithms describing car following, lane changing and gap acceptance [2].
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