Roundabout Intersections Research Articles

Particulate matter urban air pollution from traffic car

The particulate matters (PM) are very important compounds of urban air pollution. There are a lot of air pollution sources who can generate PM and one of the most important of them it is urban traffic car. Air particulate matters have a major influence on human health so everywhere are looking for PM reducing solutions. It is knows that one of the solution for reduce the PM content from car traffic on ambient urban air is the fluidity of urban traffic car by introduction the roundabout intersections. This paper want to present some particulate matter determinations for PM10 and PM2.5 conducted on the two types of urban intersection respectively traffic light and roundabout intersections in Baia Mare town in the approximate the same work conditions. The determinations were carried out using a portable particulate matter monitor Haz – Dust model EPAM – 5000, who can provide a real time data for PM10, PM 2.5.Determinations put out that there are differences between the two locations regarding the PM content on ambient air. On roundabout intersection the PM content is less than traffic light intersection for both PM10 and PM 2.5 with more than 30%.

Emission of pollution from motor vehicles with respect to selected solutions of roundabout intersections

The article concerns the assessment of emmision of selected two-lane roundabout functioning in the city of Rzeszow and its alternate turbo version. In the work was considered four scenarios that represent two different in terms of traffic congestion time of day. The results of the emission of selected components of the exhaust gas (NOx and particulates PM10) were obtained on the basis of calculations of emission model VERSIT+ Enviver. While the input data for the calculations were taken from the modeled options of roundabouts in the Vissim program. The results from the Enviver program were compared to calculations from mesoscopic model COPERT 5. The results show that the overall reduction in average speed, as well as increased frequency of braking and sudden acceleration, directly contribute to the growth of harmful emissions. However, with respect to comparision of turbo roundabout in regard of currently running two-lane roundabout can be observed reduction of selected components of exhaust gases emission about approx. 1/3.

Improving performance of roundabout intersections by optimizing traffic-flow speed

Streamlining of urban traffic influence nowadays almost everything about our modern life. The main effect, which we all feel as the daily traffic participants, either as pedestrians or vehicles drivrers, is travel time to work and back. Roundabouts intersections have a number of advantages over intersections with traffic lights, they reduce the severity of accidents, traffic speeds to provide an “calmer” road environment. So, operating performance of roundabouts are complicated, influenced by the confluence operations. The paper aims at analyzing the current situation of traffic in two crowded roundabouts in Sibiu, comparing the results with the original data and proposing solutions to improve traffic conditions and especially traffic speed. The obtained results will be the basis for improving the overall capacity of roundabouts.

Comparative life-cycle assessment of conventional (double lane) and non-conventional (turbo and flower) roundabout intersections

This research studied and compared different construction techniques for the road subgrade, embankment and pavement of different types of roundabout intersections in order to assess their environmental sustainability. A Life Cycle Assessment (LCA) was carried out on double lane, turbo- and flower roundabouts.We considered virgin materials and reclaimed asphalt pavement (RAP) for the pavement construction. Also the environmental effects due to in situ lime stabilization of fine-grained soils were assessed in order to reduce the use of virgin material in road subgrades.The use of reclaimed asphalt pavement (RAP) can lead to a significant reduction in pollutant emissions and energy consumption (especially due to the lesser material transport) – though with a slightly different impact according to the different percentages employed – compared to the pavements constructed with virgin materials. The same consideration can be made for fine soils with in situ lime stabilization: on the one hand, the technique allows to improve significantly the mechanical properties of soils which would be otherwise dumped and, on the other, to provide considerable environmental benefits. The life cycle assessment of the pavement was carried out with the help of the PaLATE software (by comparing different maintenance scenarios) while emissions and energy consumption in the use phase at intersections were evaluated by means of closed-form models (to estimate vehicle delays and speeds of vehicles) and the COPERT software.Finally, the generalized costs covered in the whole life cycle of roundabouts (i.e. sum of construction, maintenance and environmental costs) were assessed and associated to the different construction options.

Study of the opportunities of analytical determination of the origin-destination flows in roundabout intersections based on data provided by fixed observers

For the purposes of the analysis of road traffic at the level of the area surrounding a roundabout intersection there are times when the flows of Origin-Destination (O-D flows) of the respective intersection are of interest - when it is not possible to improve the level of service of the intersection by means of increasing its capacity, but only by diverting some traffic flows from the respective area. Currently, the determining of these O-D flows is based on video recordings of the intersection traffic, followed by laborious and lengthy analyses of the images obtained. But a prolific way, yet not explored in specialised literature, can be the identification of the analytic relations between O-D flow volumes and the volumes of the intersection traffic flows that can be measured by fixed observers (incoming flows, outgoing flows and conflict flows). As a result, this paper presents the research conducted to identify the possible relationships between these deterministic O-D flows and the flows that can be measured by fixed observers. It was demonstrated that, when performing measuring of the flow of vehicles that turn right with fixed observers, there will be analytical deterministic relationships for the 3-armed intersection with return flows, as well as for the 4-armed intersection without return flows. This means that, for 3-armed intersections with return flows and for 4-armed intersections without return flows, it is possible to fully know the O-D flows based on the flows measured by fixed observers (compulsorily involving right-turn flows), which is an absolutely exciting and unique achievement, as knowing these Origin-Destination flows will allow better regulation of the traffic in the area where the roundabout intersection is, in order to facilitate the upstream diversion of some of O-D flows passing through the roundabout intersection.

Cooperative Intelligence in Roundabout Intersections Using Hierarchical Fuzzy Behavior Calculation of Vehicle Speed Profile

In this paper, a new fuzzy-behavior-based algorithm for roundabout intersection management is presented. The algorithm employs cooperative intelligence and includes intelligent vehicles and infrastructure to calculate speed profiles for different vehicles, in order to achieve more comfortable driving profiles, as well to reduce congestion and CO 2 emissions. The algorithm uses adaptive spatio-temporal reservation technique and was tested in MATLAB/Simulink environment. The algorithm is designed to function in different scenarios with both cooperative and non-cooperative vehicles, as well as optional intersection infrastructure. Results have show that using the proposed algorithm different vehicle communication types can be successfully combined in order to increase traffic flow through roundabout intersections.

Autonomous Vehicle-to-Vehicle (V2V) Decision Making in Roundabout using Game Theory

Roundabout intersections promote a continuous flow of traffic. Roundabouts entry move traffic through an intersection more quickly, and with less congestion on approaching roads. With the introduction of smart vehicles and cooperative decision-making, roundabout management shortens the waiting time and leads to a more efficient traffic without breaking the traffic laws and earning penalties. This paper proposes a novel approach of cooperative behavior strategy in conflict situations between the autonomous vehicles in roundabout using game theory. The game theory presents a strategic decision-making technique between independent agents - players. Each individual player tends to achieve best payoff, by analyzing possible actions of other players and their influence on game outcome. The Prisoner's Dilemma game strategy is selected as approach to autonomous vehicle-to-vehicle (V2V) decision making at roundabout test-bed, because the commonly known traffic laws dictate certain rules of vehicle's behavior at roundabout. It is shown that, by integrating non-zero-sum game theory in autonomous vehicle-to-vehicle (V2V) decision making capabilities, the roundabout entry problem can be solved efficiently with shortened waiting times for individual autonomous vehicles.

Simulation and analysis of road construction traffic flow in urban road networks

Road construction is an important source of occasional urban road network traffic congestion. In this article, a new cellular automaton model is proposed to simulate road construction traffic flow in urban two-way-six-lane network systems with roundabout intersections. In the proposed model, a three-lane traffic rule is adopted to represent vehicle movements on road sections, turning lane changing and overtaking lane changing are allowed, and vehicle movements in intersection areas are determined by priority which relies on vehicle position. Simulation results show that increasing the closed lane number may lead to decline of the network speed. We also found that there is a relatively fixed influence range of road construction in different cases, and a proper proportion of vehicle bypass can improve the operation efficiency of road network when semi-closed construction.

Environmental, functional and economic criteria for comparing “target roundabouts” with one- or two-level roundabout intersections

The article describes a criterion based on functional, environmental and economic aspects for comparing conventional roundabouts with innovative one- or two-level roundabouts. We compared the performances of eight roundabout types, differing in geometric layout, number of lanes and traffic flow regulation from each other, with regard to vehicle delays and CO2, NOx, PM2.5 and PM10 pollutant emissions. Recently-designed roundabouts – target roundabouts and flyover roundabouts – have also been studied for their undoubted practical interest. By means of closed-form capacity models and CORINAIR methodology, several traffic simulations were carried out to examine a typical annual traffic demand curve in a suburban context, three different distribution test matrices for traffic flows (ρ1, ρ2, ρ3) and maximum annual traffic flow values Qmax ranging between 1300 and 3300veh/h.Estimating vehicle delays and annual pollutant emissions, along with construction and management costs, allowed obtaining overall costs for each roundabout examined, in function of traffic demand and several other parameters. Thanks to these analyses, we identified the roundabout types which best suit to each traffic condition.

Effect of Vehicular Traffic Volume and Composition on Carbon Emission

Road intersection is one of the causes of air pollution or toxic gases emission because at such location vehicular traffic are either required to slow down or completely stop for them to secure a safe and acceptable gap to perform a particular type of manoeuvre. The level of gaseous emissions usually increases with corresponding increase in traffic. The level of the environmental pollution depends on the type of intersection. This study evaluated the amount of carbon monoxide (CO) emissions from vehicular traffic for both morning and afternoon peak periods at roundabout and priority intersections. Carbon monoxide emissions at the intersections were first measured using GrayWolf Sensing Solution (GWSS) upon which the results obtained were used in calibrating SIDRA software for estimation of CO emission. SIDRA emission estimates were derived from traffic flow parameters; traffic volume, compositions, speeds and turning movements, as well as road geometry. Calibration factors were then derived in order to make SIDRA a reliable means for measurement of vehicle emission. Further, CO emissions traffic models were developed for the two types of intersections evaluated in this work for both morning and afternoon peak periods for two different observations periods (5 minutes and 1 hour traffic volumes) using multiple regression analysis. The models developed described how vehicular traffic volume and compositions affect CO emissions at road intersections. Further analysis revealed that roundabout is a better form of intersection as it reduces the amount of CO emission when compared to simple priority intersection.

Model of Potential Crash Rates of Rural Roundabouts with Geometrical Features

In recent years, there has been a widespread diffusion of roundabout intersections in the Italian road network; their undoubted popularity is attributable not only to their proven performance in terms of safety but also to their guarantee of smooth traffic flow. However, safety-related requirements of geometric designs are occasionally placed in a subordinate position; therefore, the success achieved by some foreign experiences has not been reached in every area. A model of potential crash rates may indicate how to modify the geometry of intersections to ensure safety. With regard to this, an example model based on the conflict opportunity technique has been developed for estimating crash rates at rural roundabouts. The model appears to respond well to traffic conditions and the geometry of roundabouts. Development of the model and results are described and analyzed in this paper.

Right-turn Bypass Lanes at Roundabouts: Geometric Schemes and Functional Analysis

Right-turn bypass lanes can be implemented in conventional and innovative roundabout intersections to increase the capacity and improve the global functional performances. The Right-turn bypass lanes (also called slip lanes) can be distinguished according to the planimetric layout and the entry control type (stop, yield slip or Free Flow acceleration lane). This paper presents a closed-form model for the estimation of capacity, delays and level of service of roundabout equipped with Right-turn bypass lanes, considering the effect of geometric slip lane schemes, control type, vehicular and pedestrian flow. In order to examine the traffic conditions which can benefit from slip lane roundabouts in terms of capacity and delays, compared to traditional schemes which have no additional lanes, a great number of analyses have been carried out by considering different O/D matrices and vehicle and pedestrian flow vectors. Such comparisons have been made by considering the control delays in function of different O/D matrices. Such O/D matrices describe the most significant situations of traffic demand which can be of interest for the road intersections under study.

Traffic Analysis in Roundabout Intersections by Image Processing

AbstractIn this paper a method for the evaluation of roundabout performance, based on the image processing of field survey data, is presented. The methodology of investigation consists of the following three main steps: a field survey to collect vehicular flow images using video cameras, the processing of images gathered by the VeTRA (Vehicle Tracking for Roundabout Analysis) software program and the analysis of the trajectories extracted. The methodology enables the automatic computation of the information required to rank and evaluate a generic roundabout: the Entry/Exit (E/E) matrix with vehicle classification (i.e. heavy, light and motorbikes), identification of vehicle trajectories, and extraction of vehicular speed/curvature diagrams along the paths inside the roundabout. The proposed image processing stage overcomes classic problems encountered with image processing such as shadows, object occlusions, and the unpredictable influence of wind or clouds. Calibration and error evaluation are obtained from data collected by a high precision GPS-RTK system mounted on a probe vehicle.

EXTENDED DIAMOND INTERCHANGES WITH ROUNDABOUTS INCLUDING LOCAL ROADS FOR RURAL CROSSINGS

This study aimed to assess operational and safety issues related to rural crossing mechanisms: a “traditional” diamond interchange design with roundabout intersections at the ramp termini, and a less conventional design incorporating local roads, called an extended diamond interchange. Various levels of traffic demand were considered through computer simulation. The primary safety metrics were the speed differences between an approaching link and a circulating link, and the speed differences between consecutive time windows on an approaching link. In both light and heavy traffic conditions, the extended diamond interchange with roundabouts including local roads seems to be safer, by these metrics, than the typical design because the longer ramp to roundabouts makes traffic flow more stable. For the operational performance, total delay time was surveyed. In heavy traffic conditions, the extended design is stronger than the typical design thanks to more space for vehicle queues.

Evaluating the Conversion of All-Way Stop-Controlled Intersections into Roundabouts

Roundabouts are becoming increasingly popular in the United States and have been considered for use at intersections facing operational or safety problems. A comparative analysis was performed on all-way stop-controlled (AWSC) intersections and roundabouts on the basis of aaSIDRA software after calibration against local conditions in Delaware and Maryland. A decision support system was developed in the form of a knowledge-based expert system on the basis of the results of the analysis to evaluate the performance of AWSC intersections and their potential success if converted into roundabouts. The results of the comparative analysis are in line with some previous researchers’ findings that AWSC intersections always perform worse than signal-controlled or roundabout type intersections under the same set of traffic conditions and geometric limitations.

An Adaptive Traffic Signaling For Roundabout With Four Approach Intersections Based On Fuzzy Logic

This research paper presents an adaptive traffic signaling method based on fuzzy logic for roundabout with four-approaches intersection. The process of whether to extend or terminate current signal phase and select the sequence of next phases is determined using fuzzy logic. The proposed method can replace an experienced traffic policeman organizing traffic at roundabout intersections.

Roundabout In-Service Safety Reviews

The number of roundabout intersections is quickly increasing around the world, mainly because of their good safety performance. However, roundabout performance can be degraded if precautions are not taken during either the design or the operation phase. Safety review methodologies are well suited for roundabout analysis, but their effectiveness can be improved substantially if the review recommendations are supported by a quantitative safety assessment. A roundabout safety assessment procedure is presented. Validation of the safety assessment procedure was carried out by a comparison of the results with empirical Bayes (EB) safety estimates. From the procedure, a safety index (SI) for roundabout approaches and for the whole number of roundabouts is assessed. The SI was assessed for 55 approaches of 15 urban roundabouts in Italy. For approaches, the correlation between the SI values and the EB safety estimates is highly significant (t = 15.62, p-value < 0.001), with 83% of the variation in the estimated number of crashes explained by the SI value. For all roundabouts, the correlation between SI values and EB safety estimates remains highly significant (t = 14.27, p-value < 0.001), with 94% of the variation in the estimated number of crashes explained by the SI value. The SI procedure makes it possible to support review recommendations by a quantitative safety evaluation. The SI can be used to rank both roundabouts and roundabout approaches by priority according to potential crash reduction from the safety measures. Furthermore, the SI procedure allows detection of safety issues that contribute the most to safety problems.

Roundabouts: Problems of and strategies for access

The increasing number of roundabout intersections is due in part to the fact that they significantly reduce death and injury rates for motor vehicle occupants. However, roundabouts can exacerbate the challenges that pedestrians with visual impairments encounter when crossing streets. Pedestrians who are blind must use their hearing to perceive gaps in traffic that are long enough to permit crossing the street, or they must detect when vehicles have yielded for them. Strategies to enhance the ability of individuals who are blind to detect gaps and to detect vehicles that have yielded for them are needed to increase access to these intersections by individuals who are blind.

Blind and Sighted Pedestrians' Judgments of Gaps in Traffic at Roundabouts

This paper reports two experiments about street crossing under conditions of free flowing traffic, with a focus on modem roundabout intersections. Experiment 1 was conducted at three roundabouts varying in size and traffic volume. Six totally blind and six sighted adults judged whether gaps in traffic were long enough to permit crossing to the median (splitter) island before the next vehicle arrived. Gap distributions and measures of judgment quality are reported. Overall, blind participants were about 2.5 times less likely to make correct judgments than sighted participants, took longer to detect crossable gaps, and were more likely to miss crossable gaps altogether. However, the differences were significant only at the two higher volume roundabouts. In Experiment 2, we evaluated the response of drivers to pedestrians with and without mobility devices (i.e., long canes, dog guides). The experiment was conducted at a single-lane roundabout, a midblock crossing, and a two-way-stop-controlled intersection. Site-specific characteristics appeared to have a greater impact on drivers' yielding than did a mobility device. Actual or potential applications of this research include the development of methods for assessing pedestrian safety and driver behavior as well as identifying intersections that may require modification in order to be accessible to blind pedestrians.

Modeling Traffic Flow and Management at Un-signalized, Signalized and Roundabout Road Intersections

Traffic congestion continues to hinder economic and social development and also has a negative impact on the environment. A simple mathematical model is used to analyze the different types of road intersections in terms of their Performance in relation to managing traffic congestion and to establish the condition for stability of the road intersections after sufficiently longer periods of time (steady-state). In the analysis, single and double lane un-signalized, signalized and roundabout intersections are evaluated on the basis of their performance (expected number of vehicles and waiting time). Experimental scenarios are carefully designed to analyze the performance of the different types of intersections. It is noted that under light traffic, roundabout intersections perform better than un-signalized and signalized in terms of easing congestion. However under heavy traffic, signalized intersection perform better in terms of easing traffic congestion compared to un-signalized and roundabout intersections. It is further noted that for stability of a road intersection, the proportion of the time a road link stopping at an intersection is delayed should not exceed the utilization factor (the ratio of the arrival rate of vehicles to the product of number of service channels and service rate).