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Developing crash modification factors for roundabouts using a cross-sectional method

Journal of Traffic and Transportation Engineering(English Edition) 2020年第3期7卷 362-374页

作者： Mohammad Nour Al-Marafi Kathirgamalingam Somasundaraswaran Ron Ayers School of Civil Engineering and Surveying Faculty of HealthEngineering and SciencesUniversity of Southern QueenslandT oow oom baQLD 4350Australia

The objective of the current study was to evaluate traffic and geometric features and their influences on the safety performance of roundabouts by developing suitable crash modification factors(CMFs).The cross-sectional method can be applied as an alternative method to estimate the CMFs when before-and-after studies are impractical to apply,e.g.,lack of data from the period after implementing treatments.To accomplish the study objective,CMFs were derived from generalised linear models(GLMs),i.e.,negative binomial(NB)regression,using data collected on regional roundabouts in Toowoomba City,Australia.Six years of crash data from 49 roundabouts included all recorded crashes as well as traffic and geometric features for the entire roundabouts.Several candidate models were developed using the GLMs.Five models were selected based on statistical significance,goodness-of-fit(GOF)measures,and cumulative residual(CURE)analysis.The results show that increasing the number of entry lanes,entry width,entry radius,traffic volume,circulatory roadway width,weaving width,and speed limit have positive effects on roundabout safety.On the other hand,increasing the number of legs,number of exit lanes,exit width,exit radius,weaving length,central island diameters,and presence of fixed object on a central island have negative effects on roundabout safety.The study shows that quantifying the risk factors can support road safety stakeholders to identify safety improvements at roundabouts more effectively and efficiently.

关键词： Safety performance Generalised linear models Crash modification factors Cross-sectional method roundabouts

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nvestigating the role of exiting vehicles and turn indicator usage in gap acceptance at single-lane roundabouts

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Frontiers of Structural and Civil Engineering 2017年第1期11卷 8-16页

作者： Nathan P. BELZ Civil and Environmental Engineering University of Alaska - Fairbanks Fairbanks AK 99775-5960 USA

roundabouts are becoming a preferred form of intersection control type due to their safety and capacity benefits. Yield control at roundabout entries inherently reduces fuel consumption and emissions when compared to other conventional intersection types. However, these benefits can be limited by poor driver behavior and judgment when entering the roundabout. This research addresses the nature of gap distributions and use of turn indicators by exiting vehicles at three single-lane roundabouts in Vermont, New York, and Alaska. Presented here is a comparison of vehicle headways measured at two different locations in each roundabout. Rejected headways are analyzed in the context of priority abstaining events when entering drivers yield to vehicles exiting on the same leg of the roundabout suggesting that ＂true＂ critical gaps are being overestimated. Results indicate that exiting vehicles, particularly those that do not use their turn indicators when departing from the major-stream of traffic have an influence on the entry decision of drivers on the same approach. This behavior is of particular concern for intersection efficiency （i.e., delay） and sustainability （i.e., excess fuel consumption and emissions）. Results prompt the consideration of more consistent guidance on and enforcement of turn indicator use during roundabout negotiations.

关键词： roundabouts exiting vehicles turn indicator use headways

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Effects of calibration process on the simulation of rear-end conflicts at roundabouts

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Journal of Traffic and Transportation Engineering(English Edition) 2019年第2期6卷 175-184页

作者： Vincenzo Gallelli Giuseppe Guido Alessandro Vitale Rosolino Vaiana Department of Civil Engineering University of Calabria

A methodology for calibrating and validating VISSIM simulation model is presented that allows to replicate the observed vehicles conflicts. A roundabout case study has been selected to test the usefulness of a combined approach of VISSIM simulation package and the surrogate safety assessment model(SSAM) for providing reliable estimates of traffic conflicts. Safety performance has been assessed from the field by video-recording vehicle interactions at the roundabout, and then expressed in terms of time to collision(TTC)values.The proposed calibration procedure has been performed by a multistage methodology involving microscopic drivers' car following behavior parameters to enhance the correlation between observed and simulated queue lengths at the roundabout's entries. The calibration procedure is based on a statistical screening of inputs leading to a linear expression relating significant parameters to the queue length. The best estimates of the model's parameters have been determined using a genetic algorithm technique.The spatial distribution of the rear-end conflicts and the TTC values determined by SSAM have been finally compared with the observed ones to analyze the capability of the model of replicating rear-end conflicts.The results suggest to this calibration procedure impacts positively on the estimate of the safety performance measures obtained through the simulation processes.Notwithstanding the good results in the evaluation of the model's accuracy, the simulation seems to fail in reproducing the traffic phenomena linked to unusual driving behavior, and therefore it is not able to replicate forced drivers' maneuvers that can lead to a conflict situation.

关键词： Simulation Safety performance Unmanned aerial vehicle roundabouts Traffic conflicts

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Evaluation and Improvement of roundabouts in Changchun

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World Journal of Engineering and Technology 2016年第3期4卷 40-50页

作者： Mo Zhou Lili Yang Hoong Chor Chin Department of Civil & Environmental Engineering National University of Singapore Singapore City Singapore Institute of Transportation Jilin University Changchun China

In Changchun, China, roundabouts are fairly common. They are often designed to connect the main roads because of their ability to reduce conflict points, making them safer than other intersections. They can also beautify the city when the central islands are landscaped. However, with increasing traffic, they may not function well and may even paralyze the road network. This means that it is important to evaluate the performance of roundabouts promptly, and to make necessary improvements if required. Using several roundabouts in Changchun as case studies, this article uses V/C ratio and delay to evaluate roundabout performance. Based on the result of evaluation, the micro-simulation model of the poorly-performing roundabout is built and enhancement is proposed.

关键词： roundabouts V/C Ratio and Delay Evaluation Traffic Simulation AIMSUN

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Trucks at roundabouts: A Synthesis Study

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Journal of Transportation Technologies 2018年第1期8卷 65-74页

作者： Pavan Kumar Chevuri Department of Civil Engineering St. Ann’s College of Engineering and Technology Chirala India

roundabouts in United States and other countries have been proved to be very successful, effective, and a safe traffic control treatment. roundabouts in the context of regularly expected truck configuration have also been successful for effective roundabout designs;however, there are always some site specific issues for trucks accommodation at roundabouts. Therefore, there is a great need for an informational guide in the form of synthesis report for roundabout designs specific to unique trucking traffic activity. While there are not significant literatures and studies in this subject, there are few studies/reports spread out which address various issues in this subject area. This study attempts to synthesize the research and knowledge of truck accommodation at roundabouts by synthesizing various research studies, reports, and articles;various subject areas such as roundabout designs for trucking activity, roundabout designs and accommodation strategies for specialized trucking activity such as oversized trucks, truck safety at roundabouts, and motor carrier perspective of trucking at roundabouts have been analyzed and relevant knowledge has been synthesized. This synthesis can be useful o researchers, designers, planners, and decision makers to determine effective ways to address specific trucking related issues at a roundabout.

关键词： roundabouts and Trucks Oversized Trucks Rural Intersections Trucking Issues at Intersections

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Integrating roundabouts with Freight Roadway Networks

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Smart Grid and Renewable Energy 2015年第10期6卷 293-302页

作者： Ranjit Prasad Godavarthy Eugene R. Russell Upper Great Plains Transportation Institute North Dakota State University Fargo USA Department of Civil Engineering Kansas State University Manhattan USA

The demand for freight transportation in the United States has grown rapidly in the past couple of decades;the rate at which the highway capacity is growing is not able to meet the freight-trans- portation needs, resulting in congestion and delay, ultimately affecting the users and the public with increased prices for the goods delivered, unreliable delivery times, and air-pollution concerns. Freight bottlenecks are a major cause of recurring congestion which accounts for about 40% of total vehicle hours of delay in the United States. Intersections for urban freight-roadway networks are one of the major freight bottlenecks and are considered to be a significant contributor for congestion and delay. Improving the efficiency at urban intersections with high truck traffic can address the freight-traffic congestion, leading to optimized goods movement as well as decreased delays, congestion, and emissions, thus enhancing the air quality in and around the communities. With the roundabout intersection control being proven as a safe, operationally efficient, and environment-friendly control treatment, a greater use of roundabouts with urban freight- roadway networks and their feasibility is analyzed in this study. The control for most urban intersections is a signalized treatment;a performance analysis is conducted for selected signalized intersections in urban freight-roadway networks, comparing the intersections by adapting a roundabout control theoretically using SIDRA (signalized and un-signalized intersection design and research aid) Intersection software. Various parameters, such as the intersection’s level of service, the effective intersection capacity, the average control delay, vehicular emissions [carbon dioxide (CO2), hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx)], the intersection’s annual delay, and the intersection’s annual cost, are selected for comparison.

关键词： Congestion on Roads and Highways Modern roundabouts Truck and Vehicular Emissions

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Roundabout’s Impact on Nearby Businesses

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Journal of Transportation Technologies 2016年第4期6卷 181-191页

作者： Ranjit Prasad Godavarthy Babak Mirzazadeh Eugene R. Russell Dean Landman Upper Great Plains Transportation Institute North Dakota State University Fargo USA Department of Civil Engineering Kansas State University Manhattan USA

The objective of this study is to determine if installation of roundabouts in a business area or on business corridors can be good for the businesses as well as improve the traffic flow in that area. This objective is achieved by emphasizing on roundabouts located in Kansas cities, particularly Topeka, Kansas. The study concentrates on conducting survey of businesses around the roundabout corridors in different places in the US including Topeka (Kansas), Junction City (Kansas), Newton (Kansas), and Carmel (Indiana). The survey results indicated a positive impact of roundabouts on businesses and traffic movement. Further, as there is no before and after corridor data available for making definite conclusions, a business corridor in Topeka, Kansas is simulated using both SIDRA and VISSIM software to evaluate the impacts of converting several traditional intersections in the corridor to roundabouts. The results from the simulation tasks have showed substantial reductions in vehicle delay and queuing for most of the traffic movements. Therefore, it was concluded that roundabouts on businesses corridor have a positive impact on traffic flows and business.

关键词： Business Performance roundabouts Traffic Flow SIDRA Analysis

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Respiratory Symptoms Associated with Workplaces Located along a Road with High-Traffic at Cotonou, Benin

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Open Journal of Respiratory Diseases 2020年第2期10卷 32-42页

作者： Parfait Houngbégnon Hervé Lawin Marius Kêdoté Affoussatou Amadou Eloic Atindegla Benjamin Fayomi Simplice Dossou-Gbété Victoire Agueh Institut Régional de Santé Publique University of Abomey-CalaviOuidahBenin EcoHealth Chair Faculty of Health SciencesUniversity of Abomey-CalaviCotonouBenin Institut de Recherche Clinique du Bénin Abomey-CalaviBenin Unitéde Recherche en Microbiologie Appliquée et Pharmacologie des substances naturelles University of Abomey-CalaviAbomey-CalaviBenin Laboratoire de Mathématiques et leurs Applications de Pau(LMAP)UMR CNRS Universitéde Pau et des pays de l’AdourPauFrance

Objective: Air pollution is becoming one of the public concerns requiring urgent feasible response per local context. Defining accurately the level of exposure of outdoor air pollution effect on health of venders working along main roads and roundabouts with high traffic is important. This study was conducted to assess respiratory health risks on venders associated with different geographical positions in Cotonou. Methods: A cross-sectional study was conducted along the main road with high traffic including three roundabouts in Cotonou. The 194 study participants from all shops, one respondent per shop, were given a unique GPS data associated to indicate the shop’s geographical position. The study employed validated questionnaire on respiratory symptoms. Results: Study participants had mean age of 36.26 (±11.65) years with sex ratio of (M/F) 1.8. Majority (72.7%) of study participates reported to have at least one respiratory symptom and 69% of them were working in non-ventilated rooms. The proportion of having at least one respiratory symptom was significantly different (p Conclusion: Working in roundabout is associated with more respiratory symptoms than working in shops along main road. Air pollution mitigation efforts should focus in such settings, taking into account the sub-population of workers in resource limited countries.

关键词： Air Pollution High Traffic roundabouts Vendors Health Risk Symptom

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