Analysis of Non-Conventional Roundabouts Performances through Microscopic Traffic Simulation (original) (raw)
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Methodological Approach for Evaluation of Roundabout Performances through Microsimulation
Applied Mechanics and Materials, 2013
In the literature, there are many methodologies that allow the evaluation of roundabout performances (Capacity, Levels Of Service, etc.): analytical models (HCM, HBS etc.), statistical models (TRRL, SETRA) etc. Each technique considers some aspects of the roundabout in comparison to others (geometric elements, vehicular flow and behavioral parameters). Obtained results are often not comparable among themselves because of distinctive peculiarities of each method. Today, the best way to solve this problem is by using a refined simulation software of vehicular circulation. However, along with a more and more refined analysis of microsimulation software algorithms, it is frequently necessary for each user (researcher, engineer, planner, etc.) to know the real sensitivity of these packages with regard to the most important key parameters. In this paper the Authors introduce the results of a wide survey conducted on an ample range of virtual roundabout scenarios by the use of a modern simulation software. Each scenario describes a fixed roundabout phenomenon using the following variables: geometric elements (inscribed circle radius, circulatory roadway, central and splitter islands etc.); characteristics of the traffic flow (dynamic traffic assignment, approach speed, circulatory speed and reduced speed zones, etc.); behavioral features (priority rules, minimum gap, minimum headway, etc.). The results are presented from the evaluation of stop-line delays.
The performance of roundabouts can affect urban transport systems in terms of environmental and operational impacts, safety and efficiency. The development of roundabout traffic management and control systems can be carried out through road traffic micro-simulation models which are computer models where the movements of individual vehicles travelling around road networks are determined by using simple car following, lane changing and gap acceptance rules. Unfortunately, despite the great diffusion of these tools, appropriate methods are still needed in order to validate and calibrate these models. In general, the calibration process can be defined in this way: the process of comparing model parameters with real-world data to ensure that the model realistically represents the traffic environment. The objective is to minimize the discrepancy between model results and measurements or observations. The aim of this paper is the presentation of a first comparative approach between observed performances and performances obtained by the use of popular microsimulation software, in particular urban intersections such as roundabouts. In particular, an experimental investigation is designed and carried out in order to acquire some vehicular parameters for a roundabout placed in an urban contest of southern Italy. The calibration process is carried out by an analysis of variance of the kinematic parameters of an n-tuple of roundabout scenarios. This calibration procedure has permitted to derive some important conclusions about the choice of the most significant input parameters for the output results of each simulation scenario. Outcomes of this study are expected to benefit both practitioners and researchers.
Alternatives to improve operational traffic in roundabouts using microsimulation
Respuestas, 2020
Roundabout in urban arterials is likely to block roads or generate long queues of vehicles due to the constant changes in urban dynamics near to the interception. Several alternatives to modify the flow pattern or geometry and infrastructure need to study previously to propose a final design solution for a roundabout with traffic issues. In this study, a review of three alternatives to improve the operational traffic are discussed; signalized intersection, turbo-roundabouts, and overpass/underpass. Also, the application of these alternatives is evaluated in a “classic” roundabout located at Tunja city that has a maximum of 3691 Veh/h counted, and it is operated in a saturated condition. Micro simulation is used from a calibrated model with volume counted, vehicle composition, and speeds in the VISSIM software. Results show that signalize the roundabout does not improve the operational traffic (with a reduction of 38% of approach speed) and, the turbo-roundabouts are a mid-term solution that meets the traffic demand on 15 years with a progressive loss of service (with a mean approach speed of 6.4 Km/h at 15 years). The constructions of underpass and overpass show to be the only solution that increases four times the travel speed throw the roundabout and keep the acceptable speed at the end of cyclic live of intersection (18.7 Km/h at 20 years).
Using a Microsimulation Traffic Model to Compare Two-Lane and Turbo-Roundabouts
Elektronički časopis građevinskog fakulteta Osijek, 2015
Microsimulation traffic models are used to analyze and predict the functionality and safety of traffic networks, especially in critical areas such as intersections. These models have proven particularly useful in analyzing and comparing solutions in the early stages of design. In this paper, we compare the functional characteristics of an existing two-lane roundabout and a proposed replacement turbo roundabout. Our microsimulation modeling used the VISSIM traffic model, and we designed the conceptual turbo roundabout with AutoCAD and TORUS5 Roundabouts software.
Evaluation of Roundabout Performances Using a Micro-Simulation Software
The growing use of roundabout to solve traffic problems has given rise to a large number of models to predict the performances of a roundabout. Each of these ones allows estimation of several features, such as capacity, approach delays and queue lengths through probabilistic or statistical formulations. The restrictions of these models, as well as the difficulty of their use, especially during oversaturation conditions, have driven researchers to use software that can simulate roundabout users behavior. In this regard the Authors present an extensive campaign of research based on several scenarios of roundabout with the aid of VISSIM micro-simulation tool. So three separate sets of scenarios for single-lane roundabouts are composed and analyzed, in total, 288 scenarios, considering as variables both the geometric features (width of splitter island, external roundabout radius, width of circulatory roadway) and the characteristics of traffic flow (distribution and assignment) and the circulation rules (approach and circulatory speed, priority rules). The evaluation of approach delay for each scenario allows to show the results in terms of level of service offered according to HCM 2010.
Sustainability, 2017
Standard" roundabouts, for example those designed in some European countries, can often be characterized by low levels of safety or capacity and a high degree of sustainability. Given the proliferation of newer layouts, it is of interest to explore whether design practices could be improved by capitalizing on the experience gained internationally. Operational aspects of some of these designs have been explored previously, but there is a need to compare both the operational and safety performance of new designs to that of standard roundabouts. The objective of this paper is to evaluate the safety and operational implications of various potential alternatives to the standard roundabouts that proliferate in Europe and elsewhere. Microsimulation is used to simulate traffic operations at roundabout layout alternatives at the same levels of volume to capacity (V/C) ratio and also with the same traffic flow. Operational performance measures include the common level of service parameters, while measures of safety are based initially on time to collision (TTC) values. Threshold values of TTC were then applied in defining conflicts that are used for crash-based safety evaluation by applying crash-conflict models estimated in published research. Interesting insights were revealed, suggesting that the newer layouts should be considered where warranted by cost-benefit considerations.
Operating speed profiles approaching a roundabout: experiments and micro-simulation
It is well known that roundabouts performance can affect urban transport systems in terms of safety, environmental and operational impacts. Roundabout traffic management and control can be carried out by using road traffic microsimulation models. Unfortunately, for these tools appropriate methods are still needed in order to validate and calibrate these models. On the other hand, the operating speed-profile is a useful tool for the analysis of safety issues on existing roads or intersections. As far as a roundabout is present, models and tools are needed to estimate a reliable operating speed-profile on the road section along which driver speed behaviour is affected by the intersection. Consequently, the object of the paper is to analyse operating speed vs. geometry relationship and to calibrate a micro-simulation model, based on experimental investigations and simulations. In light of the above fact, driver speed behaviour (approaching and departing from roundabouts) was studied and a procedure to predict the operating speed-profile along a road section characterized by the presence of a roundabout was developed. A traffic micro-simulation model was used and its results were compared with experimental data. Micro-simulation outputs and data modelling permitted to derive some important conclusions about operating speed-profiles of each simulation scenario. Outcomes of this study are expected to benefit both practitioners and researchers.