Roundabouts: Traffic Simulations of Connected and Automated Vehicles—A State of the Art (original) (raw)
Related papers
Simulation of Observed Traffic Conditions on Roundabouts by Dedicated Software
Procedia - Social and Behavioral Sciences, 2012
This study presents a calibration procedure between observed performances of a roundabout and performances obtained by the use of simulation software. Two sets of scenarios different among them only for the traffic flow distribution were analyzed: Free Flow Condition (FFC), from which to derive the average speed profiles along a through movement; and Saturation Flow Condition (SFC), to determine the average stop-line delay along a branch. A multitude of scenarios for single-lane roundabouts has been composed and analyzed in order to evaluate the best combinations of software parameters in the simulation and to minimize errors between observed and simulated performances. 743 Vaiana R. et al. / Procedia -Social and Behavioral Sciences 53 ( 2012 ) 742 -754 represent local traffic conditions. For this reason, it is important for models users to know the real sensitivity of each package on the key input and output parameters which are of interest to the practitioners (researchers, engineers, planners, etc.).
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.
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.
Evaluation and Simulation of New Roundabouts Traffic Parameters by Aimsun Software
Journal of civil Engineering and Materials Application, 2018
New roundabouts are innovation and revolutionary in roundabout design, with the risk of incidents in these roundabouts far less than traditional common roundabouts. These types of roundabouts control the traffic flow at the entrance and exit of the roundabout, with the guidance of drivers to isolated lines before entering the roundabout and guidance to the spiral lines inside the roundabout as channelized. Another advantage of these roundabouts is the much more balanced division of traffic flows than traditional ones. In Iran, in view of the many problems of capacity, flow and safety of intersections and intersections, this type of roundabout can be very useful in certain conditions. In this research, how these roundabouts are compared and also the comparison of different input capacities based on the origin-destination demand matrix for new roundabouts and common roundabouts of two lanes with the help of Aimsun traffic simulation software have been investigated. For this purpose, the values of traffic indicators of delay time, density, flow, stop time and travel time of computer simulations for new roundabouts and common roundabouts have been investigated and compared. According to the demand matrix of the origin-destination models loaded in the software and comparisons done, the optimal model for the highest capacity and the lowest delay time and travel time is presented. In this simulation, 8 to 16 percent increase in traffic flow and a decrease of 34 to 59 percent for travel time and delay time in the new roundabouts is shown in comparison with the common two-lane roundabouts.
A computer simulation model for single-lane roundabouts
Existing roundabout analysis software packages provide estimates of capacity and performance characteristics. This includes characteristics such as delay, queue lengths, stop rates, effects of heavy vehicles, crash frequencies, and geometric delays, as well as fuel consumption, pollutant emissions and operating costs for roundabouts. None of these software packages, however, are capable of determining the effects of various pedestrian crossing locations, nor the effect of different bicycle treatments on the performance of roundabouts. The objective of this research is to develop simulation models capable of determining the effect of various pedestrian and bicycle treatments at single-lane roundabouts. To achieve this, four models were developed. The first model simulates a single-lane roundabout without bicycle and pedestrian traffic. The second model simulates a single-lane roundabout with a pedestrian crossing and mixed flow bicyclists. The third model simulates a singlelane roundabout with a combined pedestrian and bicycle crossing, while the fourth model simulates a single-lane roundabout with a pedestrian crossing and a bicycle lane at the outer perimeter of the roundabout for the bicycles. Traffic data was collected at a modern roundabout in Boca Raton, Florida. The results of this effort show that installing a pedestrian crossing on the roundabout approach will have a negative impact on the entry flow, while the downstream approach will benefit from the newly created gaps by pedestrians. Also, it was concluded that a bicycle lane configuration is more beneficial for all users of the roundabout instead of the mixed flow or combined crossing. Installing the pedestrian crossing at one-car length is more viii beneficial for pedestrians than twoand three-car lengths. Finally, it was concluded that the effect of the pedestrian crossing on the vehicle queues diminishes as the distance between the crossing and the roundabout increases.
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.
Impact of Autonomous Vehicles on Roundabout Capacity
Sustainability, 2022
Studying the impact of AVs on our road infrastructure offers a lot of potential in the transportation domain; one of these issues is how capacity will be affected. This paper presents a contribution to this research area by investigating the impact of AVs on the capacity of single-lane roundabouts using a microsimulation model. For the development of the model, a roundabout situated in Győr (Hungary) was selected and field data on the roundabout geometric characteristics as well as traffic volumes were used. Simulations using Vissim were run for various scenarios based on varying input traffic volumes and market penetration rates of AVs to assess queue lengths. The highway capacity manual (HCM) roundabout model was used to estimate the capacity of the existing roundabout. Values of follow-up times and critical gaps were set to decreasing as the penetration rate of AVs increases. The results demonstrated that 20% and 40% AVs in the flow would increase leg capacities by about 10% and ...
Introduction of Autonomous Vehicles: Roundabouts Design and Safety Performance Evaluation
Sustainability, 2018
Driving experiences provided by the introduction of new vehicle technologies are directly impacting the criteria for road network design. New criteria should be taken into consideration by designers, researchers and car owners in order to assure traffic safety in changed conditions that will appear with, for example, introduction of Autonomous Vehicles (AVs) in everyday traffic. In this paper, roundabout safety level is analysed on the originally developed microsimulation model in circumstances where different numbers of AVs vehicles are mixed with Conventional Vehicles (CVs). Field data about speed and traffic volumes from existing roundabouts in Croatia were used for development of the model. The simulations done with the Surrogate Safety Assessment Model (SSAM) give some relevant highlights on how the introduction of AVs could change both operational and safety parameters at roundabouts. To further explore the effects on safety of roundabouts with the introduction of different shares of AVs, hypothetical safety treatments could be tested to explore whether their effects may change, leading to the estimation of a new set of Crash Modification Factors.