Lane-Based Micro-Analytical Model of a Roundabout Corridor (original) (raw)

Modelling Traffic Flow at Multi-Lane Urban Roundabouts

International Journal of Modern Physics C

This paper proposes Multi-stream Minimum Acceptable Space (MMAS) Cellular Automata (CA) models to study unsignalised multi-lane (two- or three-lane) urban roundabouts. Through detailed space considerations, using Cellular Automata (CA) and the Multi-stream Minimum Acceptable Space method, heterogeneity and inconsistency of driver behavior and interactions in cross traffic at entrances of roundabouts are simulated by incorporation of four different categories of driver behavior (i.e., conservative, moderate, urgent and radical), together with reassignment of categories with given probabilities at each time step. The method is able to reproduce many features of urban traffic, for which gap-acceptance models are not robust. Multi-lane roundabout models, in particular for two-lane roundabouts, are developed with different vehicle lane-allocation patterns. Various properties of multi-lane roundabout operations have been explored including throughput, turning rates, critical arrival rates...

Estimating Traffic Operations at Multi-Lane Roundabouts: A Case Study

Journal of Engineering and Applied Sciences, 2014

This paper addresses traffic modeling issues at urban multi-lane roundabouts where, despite circulating vehicles have priority, negotiation of the right-of-way can occur between antagonist traffic flows, as a result of minor drivers’ failing to obey the nominal operating rule (stop or yield control). Existing models for the estimation of operational performances have the shortcoming of not representing the interdependencies between entering and circulating vehicles at multi-lane roundabouts. An analytical capacity model derived from field observations was developed for this kind of intersections in a previous study. The complexity of the model lies in the difficulty of observing the behavioral parameters which are needed to implement the model. A procedure to get unknown behavioral parameters from traffic surveys is here proposed. This concerns saturation headways, often eluding direct observations due to rare occurrences of traffic conditions in which they can be observed. The unkn...

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.).

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.

Comparison of Capacity Models for Two-Lane Roundabouts

Transportation Research Record: Journal of the Transportation Research Board, 2003

Multilane roundabout capacity models are presented and contrasted in the context of a case study. A two-lane roundabout in Copenhagen, Denmark, was investigated, and data were collected that enable the estimation of critical gaps, follow-on times, entry capacity, and delay. The primary objective of this research was to evaluate the need for more complex capacity models than currently exist in order to properly represent driver gap-acceptance behavior at multilane roundabouts. The complexity arises when drivers are assumed to simultaneously accept pairs of critical gaps in the outer and inner circulating lanes before they enter the roundabout. This approach requires that circulating-lane headways and critical gaps be evaluated independently and not be superposed in a single traffic stream as most current capacity guides assume. The approach also implies that circulating-lane volume allocation can have a considerable impact on entry capacity. The field results indicated that indeed th...

Modeling traffic flow at a single-lane urban roundabout

Computer Physics Communications, 2002

In this paper, we propose a new model to study traffic flow at a single-lane urban roundabout, using a multi-state cellular automata (CA) ring under the offside-priority rule (by which a vehicle entering gives way to one already on the roundabout). Each vehicle entering the roundabout is randomly characterized by a predetermined exit with specified probability. Driver behavior at the roundabout entrance is randomly grouped into four categories based on space required to enter the roundabout. Three aspects of roundabout performance in particular have been studied. The first looks at overall throughput (the number of vehicles that navigate the roundabout in a given time). This is considered for different geometries, turning and arrival rates (vehicles arrive at random with a Poisson distribution, with parameter λ 0.5 in general for free flow). The second investigates changes in queue length, delay time and vehicle density (ratio of the number vehicles to the number of cells) for an individual road. The third considers the impact of driver choices on throughput and operation of the roundabout. We find that throughput is influenced by the topology of the roundabout and turning rates, but only incidentally by size. Throughput reaches a maximum for critical arrival rate on one or more roads. Driver behavior has considerable impact on overall performance, with rapid congestion resulting from reckless choices. Vehicles drive on the left in Ireland, but rules are generally applicable.

Micro-simulation modelling of congestion due to lane closures

Incident clearance and road work often require the closure of one or more of the available lanes on a highway. A lane-closure causes a significant capacity reduction, which often leads to heavy congestion. Simulation of congestion events due to lane-closures is relevant both for traffic and infrastructure management. This is especially valid when trucks are involved and they concentrate on bridges or in tunnels, thus generating critical situations for loading and safety. A better understanding of the effects of lane closures requires a realistic simulation of the merging manoeuvre of vehicles occurring in the proximity of the lane closure. Microsimulation allows for the motion of individual vehicles and it is therefore a suitable tool for studying traffic merging. In this paper, a micro-simulation tool made up of a car-following model and a lane-changing model is used for simulating a lane closure on a two-lane one direction stretch of road. The effects on traffic are studied, in terms of average speed, lane change rates, and truck distribution. It is found that the lane-changing model requires an appropriate parameter calibration when applied to lane-closures. These parameters are quite different from the ones reported in literature. An alternative means of causing congestion is also tested and it is found that it can replicate the overall congestion features upstream the closure. However, there are some differences about details of the traffic features.

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.

The model for determining vehicle flow at roundabout sections

Science, Engineering and Technology, 2021

This paper presents a model push on which to determine the flow rates vehicles per share on the basis of circular intersections recorded entries and exits of vehicles in the aisles. In addition it is possible to analyze the influence of individual flows at intersections capacity, and determine the number of vehicles at the intersection of routes in the knowledge of the number of vehicles leaving the intersection at the next exit. Count the number of vehicles it is easier to manually and by using new technologies. Model (MIKR) results in a longer or shorter period of time which gives both static and dynamic characteristics.

Formulation of large roundabout capacity under high demand flows

Intersections Control and Safety, 2013

Estimation of the entry capacity of roundabouts greatly varies between one method and another in their input requirements, model complexity, assumption made and estimated accuracy. Several available models for the capacity estimation at approach entries of large roundabouts are tested here and compared during high traffic demand conditions. Three models for the estimation of capacity are developed for roundabouts with dual or triple entry lanes. Fifteen roundabouts in Bahrain are used for the development of the models and for comparison purposes with various tested international models. The geometric data were gathered from the actual drawings, GIS maps, geo-referenced scaled aerial photographs and actual field measurements. The necessary traffic data were gathered during peak periods. Substantial differences in estimating capacities were observed between the various available international methods. This made the judgment of accepting or rejecting the estimated capacity difficult. The developed models fall well in between the tested international models and matched the actual data reasonably well. The methods with complicated input parameters and extensive equations as aaSIDRA, UK RODEL, French and Indian methods did not prove to be better than much simpler ones like Swiss or FHWA methods. The findings are quite essential for traffic planners in making judicious decisions regarding roundabouts' performance. There is a real need for a more consistent model for the capacity estimation of multi-lane roundabouts.