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Journal articles on the topic 'Roundabouts'
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1
Wankogere, Elisha Jackson, Valerian Kwigizile, Jun-Seok Oh, and Pavel Ikonomov. "Comparison of Driver Navigation at Turbo Roundabouts and Modern Two-Lane Roundabouts: Simulation Study." Transportation Research Record: Journal of the Transportation Research Board 2637, no. 1 (January 2017): 89–98. http://dx.doi.org/10.3141/2637-11.
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Roundabouts can be a solution to safety concerns common to conventional intersections. Recently in the United States, there has been an increase in the conversion of problematic intersections to roundabouts to improve their safety. However, there are some important considerations and challenges to make roundabouts safe for all users, especially multilane roundabouts. There may also be challenges for drivers to navigate a newly built or a new type of roundabout. Roundabout features such as pavement markings and signage play an important role in driver navigational performance. This research was an effort to evaluate new roundabout design and existing roundabout safety and operational features such as signs and pavement markings. The focus was on how such features influenced the performance of drivers, specifically at multilane roundabouts. Two-lane roundabouts and rotor turbo roundabouts were evaluated. A driving simulator was employed to test various simulation scenarios in a virtual world. The results indicate that lane keeping and higher navigation speeds are still problems at multilane roundabouts. The rotor turbo roundabout outperforms the two-lane roundabout in enabling correct lane choice and navigation speed control by drivers. Furthermore, it was found that roundabout signs and pavement markings used in the United States can be adopted for turbo roundabouts.
2
Hatami, Hadi, and Iman Aghayan. "Traffic Efficiency Evaluation of Elliptical Roundabout Compared with Modern and Turbo Roundabouts Considering Traffic Signal Control." PROMET - Traffic&Transportation 29, no. 1 (February 3, 2017): 1–11. http://dx.doi.org/10.7307/ptt.v29i1.2053.
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This paper compared the performance of elliptical roundabout with turbo and modern roundabouts. It considers the effects of increasing the central island radius and speed limit on delay and capacity. Three types of roundabouts (modern, turbo and elliptical roundabouts) with different numbers of lanes (single lane, two-lane and three-lane) were designed. Unsignalized and signalized controls were applied for these roundabouts. The robustness of the designed roundabouts was investigated for saturated and unsaturated flow conditions. Based on the obtained results, increasing the central island radius had both positive and negative effects on delay and capacity. However, a positive effect on these variables was observed in all roundabouts when increasing the speed limit. In unsignalized and signalized control under unsaturated flow conditions, a modern roundabout had lower delay time than an elliptical roundabout. Moreover, in saturated flow, the elliptical roundabout had the best performance in terms of delay. Overall, in comparison with the turbo roundabouts, modern and elliptical roundabouts had the highest capacities in unsignalized and signalized controls. This study can provide useful information for engineers who decide to design a roundabout.
3
Alluri, Priyanka, Albert Gan, Andres Diaz, and Ruth Steiner. "Safety Impacts of Access Management Features near Roundabouts." Transportation Research Record: Journal of the Transportation Research Board 2517, no. 1 (January 2015): 28–36. http://dx.doi.org/10.3141/2517-04.
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Roundabouts can better facilitate U-turns and provide better safety, especially in reducing severe crashes, than can traditional intersections. Roundabouts, instead of traditional signalized intersections, increasingly are being installed on busy arterial streets. Even though roundabouts gradually are becoming integral to regional transportation networks, no literature addresses the safety impacts of access management features such as driveways and median openings along corridors with roundabouts. The existing access management guidelines for signalized intersections are not directly applicable to roundabouts because traffic operations are different at the two types of intersections. In this study the safety impact of access features near roundabouts was investigated. In particular, three potential safety concerns associated with roundabouts were studied in commercial areas in Florida: (a) the impact of driveway corner clearances on roundabout safety, (b) the safety impact of median openings near roundabouts, and (c) the safety at roundabouts that provided direct access to activity centers. Data for the analysis reflected 131 roundabouts in commercial areas in Florida. Police reports for more than 1,000 crashes that occurred in roundabout influence areas between 2007 and 2011 were reviewed carefully to identify crash patterns and causes related to specific roundabout designs, con-figurations, and access features. Recommendations are made for access features near roundabouts in commercial areas.
4
Flannery, Aimee, and Tapan K. Datta. "Modern Roundabouts and Traffic Crash Experience in United States." Transportation Research Record: Journal of the Transportation Research Board 1553, no. 1 (January 1996): 103–9. http://dx.doi.org/10.1177/0361198196155300115.
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Roundabouts have become popular in Australia and many countries in Europe during the past few decades. In the United States of America, however, roundabouts are just beginning to be recognized as an alternative treatment for roadway intersections. An effort was made to collect traffic and traffic crash data for existing roundabouts in the United States and to perform a statistical analysis to determine the effectiveness of roundabouts as a treatment for intersecting roadways. General information about thirteen roundabouts located in Maryland, Florida, Nevada, and California was collected and is included for readers’ use. In addition, six retrofitted roundabout sites with accident data ranging from 1 to 3 years before and after were analyzed. In all but one case, the reduction in accidents for roundabout sites was in the range of 60 to 70 percent. A chi-squared test and a normal approximation test were performed using the accident data from these six roundabout sites. Both of these tests indicated a significant difference in the reduction of frequency and mean of accidents at 95 and 99 percent confidence levels, respectively, between pre-roundabout and post-roundabout periods. Results, though limited, are encouraging and in line with findings of past European and Australian studies involving roundabouts. Additional studies on the safety performance of U.S. roundabouts should be conducted in the future when more data are available to reinforce these findings.
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Guerrieri, Marco, and Ferdinando Corriere. "Estimation of Measures of Effectiveness (MOE) for the C-Roundabouts." Applied Mechanics and Materials 459 (October 2013): 569–74. http://dx.doi.org/10.4028/www.scientific.net/amm.459.569.
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The C-roundabout (cyclist roundabout) is a new multi-lane roundabout designed to improve the safety of cyclists at and make multi-lane roundabouts more cyclist-friendly. The geometric layout of C-Roundabouts allows the decrease of the vehicle speeds through the roundabout to around 30 km/h. The rare C-roundabout installations so far implemented in the world have not allowed analysing the capacity by means empirical data. In the light of this considerations, the main objective of the paper is to give a theoretical closed-form model for evaluation the measures of effectiveness MOE (capacity, delay, queues) of the C-Roundabouts.
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Guerrieri, Marco, and Ferdinando Corriere. "Calculation of Turbo-Roundabouts with Slip Lanes." Applied Mechanics and Materials 459 (October 2013): 595–600. http://dx.doi.org/10.4028/www.scientific.net/amm.459.595.
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A turbo roundabout is a particular type of roundabout where all lanes are bounded by traffic signs and by non-mountable curbs installed at entering and circulating lanes. Turbo roundabouts also have a very particular shape to accomplish the splitting of traffic streams and to prevent cars weaving through. These aspects make turbo-roundabouts more appropriate than roundabouts when a higher level of safety has to be guaranteed, particularly in presence of relevant pedestrian and two-wheels traffic volumes. Only in some traffic conditions, turbo roundabouts can offer higher capacities than conventional double-lanes roundabouts, so if more capacity must be guarantee a bypass lane can be added to the turbo roundabouts layout. This paper presents a closed-form model for the estimation of capacity, delays and level of service of turbo-roundabout equipped with Right-turn bypass lanes, considering the effect of geometric slip lane schemes, control type, vehicular and pedestrian flow.
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Tollazzi, Tomaž, Goran Jovanović, and Marko Renčelj. "New Type of Roundabout: Dual One-Lane Roundabouts on Two Levels with Right-Hand Turning Bypasses – ’’Target Roundabout’’." PROMET - Traffic&Transportation 25, no. 5 (October 27, 2013): 475–81. http://dx.doi.org/10.7307/ptt.v25i5.1230.
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The problems of low level traffic safety on multi-lane roundabouts have been resolved in various ways in different countries, usually by using alternative types of roundabouts that reduce the number of conflict points. Alternative types of roundabouts typically differ from 'normal' or 'standard' roundabouts in one or more design elements, as their implementation purposes could also be specific. Today, several different types of roundabouts are already in use ('mini', 'double mini', 'dumb-bell', those 'with joint splitter islands' ('dog-bone'), those 'with a spiralling circular carriageway' ('turbo'), those 'with depressed lanes for right-hand turners' ('flower') etc.). This paper introduces a new type of roundabout, dual one-lane roundabouts on two levels with right-hand turning bypasses, namely the 'target roundabout'. This paper describes and analyses their design, traffic safety, and capacity characteristics, compared with the standard two–lane roundabouts.
8
Macioszek, Elżbieta. "Roundabout Entry Capacity Calculation—A Case Study Based on Roundabouts in Tokyo, Japan, and Tokyo Surroundings." Sustainability 12, no. 4 (February 18, 2020): 1533. http://dx.doi.org/10.3390/su12041533.
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The article presents the calculation of roundabout entry capacity as a case study based on roundabouts located in Tokyo, Japan, and Tokyo surroundings. The analysis was conducted as part of the project entitled “Analysis of the applicability of the author’s method of roundabouts entry capacity calculation developed for the conditions prevailing in Poland to the conditions prevailing at roundabouts in Tokyo (Japan) and in the Tokyo surroundings”. The main aim and the research question was whether the author’s model of roundabouts entry capacity calculation constructed for the conditions prevailing in Poland after calibration is suitable to calculate roundabout entry capacity of roundabouts located in Tokyo and in the Tokyo surroundings. In order to perform the calibration in 2019, measurements were taken at the single-lane roundabouts located in Tokyo and Tokyo surroundings. The model calibration revealed that it is possible to evaluate the entry capacity of roundabouts located in Tokyo and in Tokyo surroundings using the author’s model.
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Ibanez, Guillermo, Tobias Meuser, Miguel A. Lopez-Carmona, and Diego Lopez-Pajares. "Synchronous Roundabouts with Rotating Priority Sectors (SYROPS): High Capacity and Safety for Conventional and Autonomous Vehicles." Electronics 9, no. 10 (October 20, 2020): 1726. http://dx.doi.org/10.3390/electronics9101726.
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Roundabouts are a highway engineering concept meant to reduce congestion and improve safety. However, experience shows that capacity of roundabouts is limited, and safety is not optimal. However, these improvements in capacity and safety should be compatible with both manually-driven and autonomous vehicles. Incorporating existing advanced technologies to the signaling and control of roundabouts will undoubtedly contribute to these improvements but should not restrict this compatibility. We approach roundabouts as synchronous switches of vehicles, and propose a roundabout system (synchronous roundabouts with rotating priorities) based on vehicle platoons arriving at the roundabout at a uniform speed and within the time slot assigned to their entry, avoiding conflicts and stops. The proposed signaling system is visual for human drivers and wireless for connected and autonomous vehicles. We evaluated analytically and with simulations roundabouts of different radii for several values of the average distance between vehicles. Results show that average delays are 28.7% lower, with negligible dispersion. The capacity improvements depend on design parameters, moderate for small roundabouts, but that goes up to 70–100% for short inter vehicular distances and medium and large roundabouts. Simulations with unbalanced traffic maintained the capacity improvement over standard roundabouts.
10
Thai Van, May-Jeanne, and Pascal Balmefrezol. "Design of Roundabouts in France: Historical Context and State of the Art." Transportation Research Record: Journal of the Transportation Research Board 1737, no. 1 (January 2000): 92–97. http://dx.doi.org/10.3141/1737-12.
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First appearing in the French highway code in 1983, roundabouts have multiplied greatly throughout France, to the currently estimated 17,000. The success of roundabouts is explained, first, by the ideal safety conditions that this type of intersection presents and, second, by the advantages roundabouts provide in speed reduction, suitability to traffic, and break effect. The growth of roundabouts in recent years has allowed better understanding of this type of layout and has enabled all uses to be tested. The rules for designing and sizing have developed to favor the construction of roundabouts that are smaller and thus easier to fit into the urban environment. Vulnerable users (pedestrians and cyclists) are catered to better. New configurations are appearing that combine traffic lights and roundabouts, and these should be investigated in depth. Furthermore, it appears that the roundabout is subject to fashion and that many changes are planned to the roundabout—forgetting that it is not always the best solution. Also, it is important to remind designers and architects of the conditions under which the roundabout actually is an adequate solution for the site in question.
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Elhassy, Zuhair, Hatem Abou-Senna, Khaled Shaaban, and Essam Radwan. "The Implications of Converting a High-Volume Multilane Roundabout into a Turbo Roundabout." Journal of Advanced Transportation 2020 (January 10, 2020): 1–12. http://dx.doi.org/10.1155/2020/5472806.
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With the growing number of vehicles utilizing roads in the city of Doha, Qatar, most intersections, particularly multilane roundabouts, have been facing traffic congestion dilemma, where traffic demand exceeds capacity. A new design for multilane roundabouts, known as a rotor turbo roundabout, was considered as an alternative to an existing highly congested multilane roundabout. The new design features spiral roadway markings and raised lane dividers which prevent maneuvering within the roundabout and eliminate cutting-offs and weavings. This design has achieved high capacity and low delay in many European countries. In this study, a traffic simulation program, VISSIM, is used to model the complex traffic operation of both the existing and proposed multilane roundabouts and to replicate the high traffic conditions and aggressive driving behavior prevalent among the Middle East countries. Three different rotor designs were examined in an attempt to have a valid comparison between the two types of roundabouts and to adhere to the standard design of the rotor roundabout without violating its essential features. The proposed designs performed slightly better on the minor approaches and managed to deliver an overall improved LOS compared to the conventional design. Major approaches, however, exhibited an increase in vehicle delay and queue lengths. The results showed that the capacity of the conventional three-lane roundabout was always superior to the capacity of the rotor roundabouts. It was concluded that rotor roundabouts may not be suitable for intersections with high demand volumes exceeding 4500 vehicles per hour, and whenever the traffic flow condition is oversaturated.
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Flannery, Aimee, Lily Elefteriadou, Paul Koza, and John McFadden. "Safety, Delay, and Capacity of Single-Lane Roundabouts in the United States." Transportation Research Record: Journal of the Transportation Research Board 1646, no. 1 (January 1998): 63–70. http://dx.doi.org/10.3141/1646-08.
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Roundabouts are a form of at-grade intersection control that is used frequently around the world and is becoming popular in the United States. Roundabouts are being used to replace two-way and all-way stopcontrolled intersections and traffic signals in the United States. Roundabouts have also been used recently in Vail, Colorado, to improve an existing stop-controlled freeway interchange system. In this study, five single-lane roundabouts are studied to assess their safety and operational performance. All five sites were stop-controlled before roundabouts were installed, and overall the sites experienced a reduction in accident frequencies, rates, and also control delay. Aside from a review of safety and delay data before and after installation of the roundabouts, this study includes a comparison of field-measured control delay with that predicted by SIDRA, an analytically based software package that can analyze at-grade sign- and signal-controlled intersections as well as roundabouts. This study will help agencies better understand their ability to predict delay at American roundabouts. Finally, findings are presented regarding the accuracy of the roundabout capacity model contained in the 1997 update to Chapter 10 of the Highway Capacity Manual. Because of the lack of roundabout entries that are operating at capacity in the United States, an approximation of potential capacity based on available gaps in the circulating stream was made. These findings indicate that the manual may be optimistic in its prediction of capacity for single-lane roundabouts in the United States; however, it should be noted that the lack of roundabout entries operating under capacity in the United States only allows for an approximation of field capacity to be made at this time.
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Clark, Ralph O., and Christopher B. Mayhorn. "Are Roundabouts Safer for Pedestrians?" Proceedings of the Human Factors and Ergonomics Society Annual Meeting 66, no. 1 (September 2022): 1746–50. http://dx.doi.org/10.1177/1071181322661059.
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Pedestrians continue to be killed and injured at the meeting points with motor vehicles. The current study explored how drivers managed the cognitive load of negotiating roundabouts. One hundred fifty-five undergraduates at a large university in the southeastern United States were recruited. Participants were given some training on driving rules concerning roundabouts and were then presented with a 25 question, multiple-choice test that served as a check on learning. The participants who passed the learning check were then presented with 80 visual stimuli of driving situations commonly encountered at roundabouts. The stimuli were presented in Qualtrics as seven traffic situations that were randomized. Results supported the hypothesis that pedestrians are not noticed at roundabouts a significant amount of time making the pedestrian/automobile interaction at roundabouts a safety hazard. Participants failed to notice pedestrians most often in roundabout entering vignettes but also failed to notice pedestrians in roundabout exiting vignettes. Results suggest participants did not notice pedestrians attempting to cross the street in crosswalks at roundabouts. Additional research is needed to study how to increase visibility of pedestrian crossing in roundabouts. The findings of this study will raise awareness of the increased need for pedestrian safety measures at roundabouts.
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Petru, Jan, and Vladislav Krivda. "An Analysis of Turbo Roundabouts from the Perspective of Sustainability of Road Transportation." Sustainability 13, no. 4 (February 16, 2021): 2119. http://dx.doi.org/10.3390/su13042119.
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The designs of turbo roundabouts vary among countries and undesirable and potentially dangerous situations can occur for vehicles passing through the roundabout. In this article, we focus on an analysis of one of the problems within sustainable road transportation, i.e., the geometric layout of turbo roundabouts. First, we review the Czech and foreign regulations and describe the design procedures for turbo roundabouts. Studies that have been performed in the Czech Republic and abroad (the Netherlands, Slovenia, Poland, Germany, Hungary, etc.) are described. We evaluate the geometric layout of turbo roundabouts, the effectiveness of construction adjustments at the entrance to the roundabout, and an analysis of the physical separation of lanes. We present procedures and methods for measurements and assessments, which are used for evaluating the effectiveness of the geometry of a turbo roundabout. Finally, conclusions for the given hypotheses are given, as well as the importance of geometric elements (shape of the turbo roundabout, physical separation of lanes, the spike, etc.) for the actual passage of vehicles through the turbo roundabout. Furthermore, we discuss how these elements influence the safety of road traffic, the sustainability of road transportation, and the emergence of potentially dangerous situations.
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Hollenstein, Daria, Martin Hess, Denis Jordan, and Susanne Bleisch. "Investigating Roundabout Properties and Bicycle Accident Occurrence at Swiss Roundabouts: A Logistic Regression Approach." ISPRS International Journal of Geo-Information 8, no. 2 (February 18, 2019): 95. http://dx.doi.org/10.3390/ijgi8020095.
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The positive effects of active mobility on mental and physical health as well as on air quality are widely acknowledged. Increasing the share of active travel is therefore an aim in many countries. Providing bicycle-safe infrastructure is one way to promote cycling. Roundabouts are a common traffic infrastructure and are supposed to facilitate safe and smooth traffic flow. However, data on road traffic accidents indicate an over-proportional involvement of cyclists in accidents at roundabouts. In the present study, the influence of roundabout geometry and traffic flow on bicycle accident occurrence was investigated using a logistic regression approach on twelve parameters of N = 294 mostly small- and mini-sized single-lane roundabouts in the Canton of Berne, Switzerland. Average weekday motorized traffic was identified as a major factor in explaining bicycle accident occurrence at roundabouts. Further, the radius of the central island, the location of the roundabout (in town vs. out of town) and the number of legs were significantly related to bicycle accident occurrence. While these results are in general agreement with findings from similar studies, the findings regarding the central island’s radius and the number of legs underpin the need for roundabout type-specific studies: Some parameters may not prove relevant in intermediate- to large-sized roundabouts, but become critical in small or mini roundabouts, which are common in Switzerland and numerous in the present sample.
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Tollazzi, Tomaž, Marco Guerrieri, Goran Jovanović, and Marko Renčelj. "Functions, Capacities, and Traffic Safety Characteristics of Some Types of Two-Level Roundabouts." Sustainability 12, no. 17 (August 25, 2020): 6914. http://dx.doi.org/10.3390/su12176914.
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Over recent decades, roundabouts have become increasingly used when building new at-grade intersections or up-grade junctions all over the world. Consequently, control of traffic flows at at-grade intersections and up-grade junctions using roundabouts creates unique design problems. Nowadays, ‘alternative’ types of roundabouts have started to become very popular, especially because of their advantages compared with ‘standard’ roundabouts and standard types of up-grade junctions. Some of these alternative types of roundabouts are two-level roundabouts, which are still currently in the development phase. It is for this reason that they can be called ‘theoretical roundabouts’. Two-level roundabouts are particularly useful in urban and suburban areas with space limitations due to their relatively small footprint. This paper illustrates three new alternative types of two-level roundabouts—‘target’, ‘four flyover’, and ‘roundabout with left and right bypasses’—as well as their functions, capacities, and traffic safety characteristics.
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Lee, Dongmin, Sooncheon Hwang, Eunhan Ka, and Chungwon Lee. "Evaluation of the Rain Effects on Gap Acceptance Behavior at Roundabouts by a Logit Model." Journal of Advanced Transportation 2018 (July 11, 2018): 1–11. http://dx.doi.org/10.1155/2018/2726732.
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A roundabout is generally known as an efficient, safe, and environmentally friendly intersection. Since 2010, the Korea government has taken the lead in constructing roundabouts as part of a special project. During that time, many ideas have been put forward to improve the safety, operation, and design of such roundabouts. In terms of improvements, it is particularly important to understand roundabout gap acceptance behavior. As such, we investigated gap acceptance behaviors at four roundabouts based on field observation during both good weather and rainy conditions. Based on the observed data, roundabout critical gaps were estimated, and a logit model for gap acceptance using various roundabout variables was developed to investigate gap acceptance maneuvering at roundabouts. A total of 2,421 data events for gap acceptance were collected from the field observation. Out of these events, 64.6% of drivers (1,564 drivers) accepted the given gaps and 35.4% of drivers (857 drivers) rejected them. The values for critical gaps were estimated using several different estimation methods and ranged from 3.3 to 4.7 seconds. The model was developed using four variables including gap size, type of circulating vehicle, traffic volume at the circulating lane, and weather conditions. The developed model shows that a longer gap results in a 3.669 times higher probability of entering roundabouts when the gap is sufficiently great for acceptance than when the gap is smaller. The effects of other variables, such as circulating vehicle types, circulating traffic volume, and weather conditions, are relatively lower than that of a gap size. Rain conditions influenced gap acceptance maneuvering around a roundabout. Drivers need about a 10 percent longer gap to accept entry into roundabouts during rainy conditions, and gap acceptance probabilities are 10 to 20 percent lower for the same given gap time during rainy conditions compared to good weather conditions.
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Suh, Wonho, Jung In Kim, Hyunmyung Kim, Joonho Ko, and Young-Joo Lee. "Mathematical Analysis for Roundabout Capacity." Mathematical Problems in Engineering 2018 (June 5, 2018): 1–8. http://dx.doi.org/10.1155/2018/4310894.
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This paper investigates roundabout capacity analysis using mathematical modelling and microscopic simulation. The capacity in approach section in roundabout is calculated by estimating the number of vehicles that can enter a roundabout for a given approach given a certain circulating volume. Since roundabouts are working with only yield conditions, capacity is dependent on gap acceptance model. Priority rules are used to simulate the gap acceptance model and define the right-of-way for conflicting movements. In the case of roundabouts, priority rules can be utilized to establish right-of-way at each of the conflict points where the approach traffic merges with the circulating traffic of the roundabout. By altering the minimum acceptable gap and related parameters, it is possible to calibrate a simulation model to be that of a real-life roundabout or that of a theoretical roundabout that meets the operating characteristics defined in current capacity models. The proposed roundabout capacity analysis methodology is expected to assist modelling operational conditions for roundabouts. Results are presented that provide evidence to validate the proposed approach.
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Mao, Chengyuan, Qin Wang, Wenjiao Xu, Xin Cheng, Shengde Yang, and Peiran Li. "Combined Phase Design Model for Multileg Roundabout Intersections." Journal of Advanced Transportation 2022 (October 3, 2022): 1–13. http://dx.doi.org/10.1155/2022/8946794.
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Multileg roundabout intersections are widely used in urban areas worldwide. However, its traffic organization and signal control are very complicated in the case of large traffic flow, and the signal optimization methods for conventional intersections are not suitable for applying directly to roundabouts due to the complexity of the operating process. Therefore, many scholars have focused on dedicated signal timing schemes for roundabouts, especially through tuning key parameters such as signal cycle and green light time. However, research and applications regarding variable phases at roundabouts are quite rare. To address this gap, this paper analyzes the traffic flow characteristics and capacity of multileg roundabouts and proposed a combined phase design model to achieve the maximum utilization of road capacity at roundabouts, which can generate the optimal phase scheme based on real-time traffic data. The feasibility of the combined phase design model is verified by a case study in Jinhua, China. The results indicate that the proposed combined phase design model can improve the applicability of actuated signal control and the reasonableness of signal timing for multileg roundabouts and thus further improve the roundabout efficiency.
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Mauro, Raffaele, Marco Cattani, and Marco Guerrieri. "Evaluation of the safety performance of turbo roundabouts by means of a potential accident rate model." BALTIC JOURNAL OF ROAD AND BRIDGE ENGINEERING 10, no. 1 (March 10, 2015): 28–38. http://dx.doi.org/10.3846/bjrbe.2015.04.
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Turbo roundabouts are a particular road intersection layout, designed to increase the safety of double-lane roundabouts, while maintaining their excellent capacity. The main feature of this new concept of roundabout is the impossibility to move from one lane to another, provided by physical barriers marking the lanes. The paper shows an application to turbo roundabouts of a potential accident rate model, aiming to evaluate their safety improvement. Themodel is based on the concept of potential conflict: each vehicle involved in a general intersection performs a series of maneuvers which potentially imply a crash, according to the actual traffic. The number of accidents related to each critical maneuver is proportional to the number of times this maneuver occurs at the intersection. In order to define the critical maneuvers, and hence the relevant potential conflicts, specific crash typologies for roundabouts are adopted. Traffic volumes are required, to evaluate the expected number of accidents, and also probabilities of accident for every critical maneuver. These ratios were obtained by a model calibration, based on actual accident and traffic data recorded on conventional single and double-lane roundabouts. The model was then used to compare four-leg turbo roundabouts to conventional roundabouts. The comparisons have taken into account only basic differences in layout, such as geometric elements, that also play a role in determining safety performances of a roundabout. The results obtained show that turbo roundabouts significantly decrease the accident rate with respect to conventional roundabouts, by eliminating conflicts between circulating and exiting vehicles.
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Abhigna, Dodappaneni, Sindhu Kondreddy, and K. V. R. Ravi Shankar. "Effect of vehicle composition and delay on roundabout capacity under mixed traffic conditions." Archives of Transport 40, no. 4 (December 1, 2016): 7–14. http://dx.doi.org/10.5604/08669546.1225456.
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Roundabouts are replacing conventional unsignalized intersections in many parts of the world (Polus and Shmueli, 1997). Capacity estimation is necessary for designing a new roundabout, to analyze and improve the existing roundabout facilities. There are several methods to estimate the capacity of the roundabout, but most of them are for homogeneous lane based traffic conditions and not applicable for mixed traffic conditions. This study tries to find out the applicability of the existing methods to mixed traffic conditions, identify the effect of vehicle composition, travel time and delay on capacity. In this study, data was collected from two roundabouts located in Mysore, Karnataka and Rajahmundry, Andhra Pradesh in India. Capacities for both the roundabouts are calculated using the existing methods and compared. VISSIM simulation model has been developed and analyzed for different vehicle compositions scenarios. It was observed that vehicle composition of the traffic influences the roundabout capacity. Since the entry capacity of a roundabout varies significantly with the vehicle composition of the traffic at the roundabout, it is necessary to incorporate this factor into the existing capacity estimation models.
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Kovács, Tamás. "Computer simulation of roundabouts." Gradus 7, no. 3 (2020): 153–58. http://dx.doi.org/10.47833/2020.3.csc.003.
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Inthe last decades numerous traffic lamp controlled intersectionshave beenchanged to roundabouts on Hungarian traffic roads, hoping that this helps diminish the usual traffic jams in these traffic contexts.The most characteristic parameter of a roundabout is the capacity that is the number of vehicles can pass through the intersection in 1 hour. The capacity calculation of the new roundabouts, beyond a formula basedcalculation, often involves computer simulation as well, so as to get more reliable results. In the present paper we introduce a development of our traffic simulator so that it is able to determine the capacitiesof a roundabout. The simulation is tested by capacity calculation of a real roundabout and the dependency of the capacity on some key parameters is examined as well.
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Shaaban, Khaled, and Hassan Hamad. "Group Gap Acceptance: A New Method to Analyze Driver Behavior and Estimate the Critical Gap at Multilane Roundabouts." Journal of Advanced Transportation 2018 (2018): 1–9. http://dx.doi.org/10.1155/2018/1350679.
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The operations of multilane roundabouts, especially three-lane roundabouts, are unique and more complicated than any other type of roundabouts. This study aims to analyze driver behavior and estimate the critical gap at three-lane roundabouts. Video data were collected at two roundabouts. The analysis identified a pattern of group gap acceptance, where vehicles entering the roundabout from different lanes moved in groups during the same gap. In this case, the decision of vehicles entering from outside lanes greatly depended on the gap acceptance decision of vehicles in the inside lane. Analysis showed that the vast majority of the vehicles accept the gap in groups and the critical gap was estimated accordingly. The study provides a new explanation for the operation at multilane roundabouts. The use of this simple method is recommended when estimating critical gaps for multilane roundabouts.
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Johnson, Mark T. "Safety Impacts of Signing and Pavement Markings on Property-Damage-Only Crashes at Multi-Lane Roundabouts." Transportation Research Record: Journal of the Transportation Research Board 2673, no. 2 (January 25, 2019): 477–88. http://dx.doi.org/10.1177/0361198118823738.
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Conventional intersections that have been replaced by multi-lane roundabouts have experienced a substantial reduction in both injury and fatal crashes. Property-damage-only (PDO) crashes have also been reduced at some of these roundabouts. However, some have experienced a significant increase in PDO crashes. This has caused some jurisdictions to question the suitability of multi-lane roundabouts despite their benefit of reduced injury and fatal crashes. The question arises as to why some U.S. multi-lane roundabouts have high numbers of PDO crashes whereas other outwardly similar roundabouts do not. This paper examines the hypothesis that the cause of the higher numbers of PDO crashes at some U.S. multi-lane roundabouts is driver confusion and information overload, arising from a combination of poor geometric layout, signing, and pavement markings. Successful roundabout design requires that the geometric layout, the signing, and the pavement markings act together to give a simple, clear message to the drivers, thereby avoiding driver confusion and reducing PDO crashes. This paper reviews research and explores the best practice for roundabout signing and pavement marking using established traffic engineering principles and discusses aspects of the 2009 Manual on Uniform Traffic Control Devices that may contradict these principles. The paper highlights two case studies of poorly performing U.S. multi-lane roundabouts, where the revised signing and pavement markings achieved 37–80% reduction in PDO accidents.
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Gnjatović, Nikola. "Roundabouts - drivers' attitudes about the way of moving in two-lane roundabouts." Put i saobraćaj 67, no. 2 (June 14, 2021): 53–60. http://dx.doi.org/10.31075/pis.67.02.06.
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In the last few years, there has been an expansion in the construction of roundaboust. The construction of roundabouts, raised the level of traffic safety. However, it can not be said that all roundabouts have the same level of traffic safety. One-lane roundabouts belong to the category of roundabouts with the fewest points of conflict, and then follow two-lane and multi-lane roundabouts. In general, in the Republic of Srpska there are certain deficiency in the statute and regulations, which refer to this area. These deficiency bring drivers to misapprehension how they should behave at roundabouts. In this labour will be presented the data obtained by surveying with random sampling. Attitudes refer to the way of direction of drivers, only in two-lane roundabouts. Also, in the labour we will provide a suggestion of measures. The suggested measures are practical and can be relatively easily applied in our country.
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Giuffrè, O., A. Granà, T. Giuffrè, R. Marino, and S. Marino. "Flower Roundabouts And Double-Lane Roundabouts: A Comparative Performance Analysis." Archives of Civil Engineering 60, no. 3 (September 1, 2014): 349–65. http://dx.doi.org/10.2478/ace-2014-0024.
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AbstractIn the paper, a choice criterion between flower roundabouts and double-lane roundabouts is proposed, focusing on operational benefits that can derive from one scheme over the other, and outlining a general framework for benefit-cost analysis. In order to assess operational benefits of innovative roundabouts over modern roundabouts, a comparative analysis was made. Capacity was estimated using gap-acceptance models. In detail, assuming the dichotomic shifted negative exponential distribution to model headways in circulating streams, the Hagring formula was adjusted to obtain entry capacity estimations at roundabout approaches where entering vehicles face one or two conflicting flows. Based on the control delay, the suitability domains and indifference areas were constructed. Thus, a sensitivity analysis to changes in traffic demand for operational benefits of flower roundabouts over double-lane roundabouts was carried out and discussed. At last, evidence for new installations and conversion of existing roundabouts can be found.
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Salwan, Akshay, Said M. Easa, Narayana Raju, and Shriniwas Arkatkar. "Intersection Sight Distance Characteristics of Turbo Roundabouts." Designs 5, no. 1 (March 8, 2021): 16. http://dx.doi.org/10.3390/designs5010016.
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A turbo roundabout uses spiral circulatory roads for effectively counteracting the problems faced in modern multilane roundabouts. First developed in 1996, the turbo roundabout has an advantage over the conventional roundabout regarding capacity and safety. Turbo roundabouts are still in the developing phase in North America, but even in the European subcontinent where they exist in large numbers, reliable analytical studies on the critical parameters of roundabout visibility are lacking. Visibility (sight distance) helps to shape the geometry of the intersection and aids in safety. This paper presents the mathematical characteristics of the intersection geometry and intersection sight distance (ISD) of the turbo roundabout. Mathematical formulas are presented for the sight distance from the approaching vehicle to the conflicting-entering and circulating vehicles. The maximum lateral clearances to the conflicting vehicles are derived using mathematical optimization. The developed analytical method is verified graphically using AutoCAD. To assist in practical applications, design aids for the maximum lateral clearance are presented. The presented method and design aids should aid in promoting safety at turbo roundabouts.
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Gustafson, Joe. "Uniformity of Terminology for Circular Intersection Designs." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 34 (July 13, 2018): 63–72. http://dx.doi.org/10.1177/0361198118786672.
Full textAbstract:
Most transportation engineers around the world, and now in the United States, are relatively familiar with roundabouts and their operational and safety benefits. Although roundabouts are becoming increasingly common, drivers and even engineering professionals often contend with mixed messages about roundabout design and operation. In a world speckled with all manner of spiral roundabouts, signalized roundabouts, traffic circles, gyratories, and rotaries, is it any wonder that confusion, and public resistance, often persists? These mixed messages may represent the greatest hurdle to implementation, public acceptance, and safe operation of multi-lane roundabouts in particular. Within North America and across the globe, circular intersection designs that appear relatively similar to users can in fact require significantly different driver behaviors, depending on whether they are configured with a continuous circle road or a network of crossing roadways. This distinction can be of critical importance for roadway designers and agencies, elected officials and other policymakers, road user education and licensing, traffic enforcement, mapping and GPS navigation, and safe operation of autonomous vehicles. This paper aims to provide an overview of existing definitions, explore the nature of conflict points for each design, provide a framework modeling method for analysis, and provide globally applicable definitions for roundabout features for use in design, education, policy, enforcement, and research. This paper is focused primarily on roundabout design guidance and operations within the United States, but places these practices within the global context, such that the definitions and analyses provided can be applied to all forms of roundabout intersections around the world.
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Li, Zhixia, Madhav V. Chitturi, Andrea R. Bill, and David A. Noyce. "Operational Evaluation of Two-Lane Roundabouts at Freeway Ramp Terminals: Comparison Between Roundabout and Signalized Interchanges." Transportation Research Record: Journal of the Transportation Research Board 2637, no. 1 (January 2017): 99–113. http://dx.doi.org/10.3141/2637-12.
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In the United States, roundabouts have recently been constructed to replace signalized intersections at freeway ramp terminals as both a safety and an operational treatment. In practice, this treatment is in need of guidelines specifying conditions when the roundabout or signalized intersection is more appropriate to assist practitioners in deciding which alternative to choose. In particular, research providing a comprehensive operational comparison between roundabouts and signalized interchanges is lacking. The current research—though a strictly calibrated microscopic simulation platform—analyzes and models the control delay at double-lane roundabouts and signalized interchanges. Both roundabouts and signalized interchanges were modeled in a Vissim simulation platform. Capacity at each roundabout entrance was calibrated and validated separately for passenger cars and heavy vehicles, since both vehicle types have different critical and follow-up headways. The design of the simulation experiments covered 2,880 different scenarios for roundabouts and signalized interchanges with varying ramp and arterial volumes, ramp spacing, and heavy-vehicle percentages. From the simulation results, control delay and level of service of the off-ramp and arterial approaches of roundabouts and signalized diamond interchanges were modeled and compared. Ultimately, guidelines for the selection between double-lane roundabouts and signalized interchanges were developed and presented in the form of look-up tables. These tables provide an easy-to-use tool for practitioners to determine the appropriate double-lane interchange to install under specific combinations of traffic demand, heavy-vehicle percentage, and ramp spacing conditions.
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P, Nwaerema, Fred-Nwagwu WF, and Dangana K. "Spatio-temporal variability of vehicular traffic, noise and temperature of Minna City, Niger State, Nigeria." MOJ Ecology & Environmental Sciences 7, no. 1 (February 10, 2022): 7–9. http://dx.doi.org/10.15406/mojes.2022.07.00240.
Full textAbstract:
This study investigated spatio-temporal variability of vehicular traffic noise and temperature of Minna city, Niger State. The study used the 15 minutes Septa-Square technique to count the number of vehicles across the purposively selected junctions and round-abouts. The Noise Meter Level (Dosemeter) was used to generate the vehicular traffic noise at the selected junctions and roundabouts. The thermometer was used to capture the hotness of the selected roundabouts and junctions. The result of the study showed that Tunga Roundabout had 7032 vehicular counts, which was the highest vehicular traffic flow in the city. Barago Roundabout had 93.4dB recorded as the highest noise level and Tunga Roundabout recorded 360C as the highest temperature reading. The afternoon and evening had the highest records of vehicular traffic flow, increased traffic noise level and the temperature readings. The study recommended the construction of flyover to reduce traffic flow especially at Tunga and City Gate roundabouts. It recommended the construction of link roads to divert traffics to other parts of the city, plant trees at the roundabouts and junctions in order to cushion the effects of high temperature without further delay.
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Demir, Hatice G., and Yusuf K. Demir. "A Comparison of Traffic Flow Performance of Roundabouts and Signalized Intersections: A Case Study in Nigde." Open Transportation Journal 14, no. 1 (July 6, 2020): 120–32. http://dx.doi.org/10.2174/1874447802014010120.
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Background: Intersections affect the safety and capacity of urban traffic. Therefore, the design and selection of the type of intersection need to be made very carefully. According to the demand level, a different intersection can be designed. Signalized intersections are one of the intersection types in which the sequence and duration of the flow at the intersection are provided by the lights. Generally, this type of intersection is used on roads with high traffic volume. Modern roundabouts are one of the types of circular intersections that provide advantages over other types of intersection in terms of smooth operation and safety. Modern roundabouts exist in several types today worldwide. In practice, the distinction about the kinds of roundabouts would not be fully clarified; as a result, queuing and delay can be seen as negative effects. Methods: In this study, to make a distinction and clarify the kinds of roundabouts, first, the roundabouts types are introduced according to geometric and operational aspects. A signalized intersection, where a circular island is placed and also signalized, was investigated in terms of capacity, delay, and emissions located in Niğde. The traffic flow performance of the current state (nested signalized roundabout) was calculated with HCM Method (for signalized intersection) using SIDRA and compared with roundabout solutions of the intersection with HCM6 (for roundabout) method using SIDRA Intersection analysis software. Results: From the results of the intersection capacity analysis study based on HCM6, it was seen that the application of a roundabout scenario (intersection considered as a modern roundabout) showed higher performance at the intersections than the intersection having a secondary signal. Capacity increased to 67.8%, the average delay decreased to 72.8% and 95th percentile queue dropped to 82.2%. Conclusion: Roundabout controlling instead of a nested signal system can be an example of the increase in the performance of traffic flow. This highlights the importance of choosing the appropriate roundabout design.
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Xia, Qian, and Lei Shi. "An Optimized Design Scheme for Roundabout Traffic Management." Applied Mechanics and Materials 253-255 (December 2012): 1884–89. http://dx.doi.org/10.4028/www.scientific.net/amm.253-255.1884.
Full textAbstract:
Roundabouts have since become increasingly common. Statistically, roundabouts are safer for drivers and pedestrians than both traffic circles and traditional intersections. However, in the actual life, now roundabout faces the challenge that the traffic flow exceeds the limit. In order to decrease the construction cost and maximize the benefits, in accordance with the analysis of the roundabout capacity and traffic signal control, the author put forward a self-suitable red light adjustment scheme based on BP neural network. At last, integrating the roundabout traffic management system actually investigated, selecting the data to do the test to prove the validity of the mentioned scheme.
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Tulu, Getu Segni, M. Mazharul Haque, Simon Washington, and Mark J. King. "Investigating Pedestrian Injury Crashes on Modern Roundabouts in Addis Ababa, Ethiopia." Transportation Research Record: Journal of the Transportation Research Board 2512, no. 1 (January 2015): 1–10. http://dx.doi.org/10.3141/2512-01.
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Pedestrian crashes represent about 40% of total fatal crashes in low-income developing countries. Although many pedestrian crashes in these countries occur at unsignalized intersections such as roundabouts, studies focusing on this issue are limited. The objective of this study was to develop safety performance functions for pedestrian crashes at modern roundabouts to identify significant roadway geometric, traffic, and land use characteristics related to pedestrian safety. Detailed data, including various forms of exposure, geometric and traffic characteristics, and spatial factors such as proximity to schools and to drinking establishments were collected from a sample of 22 modern roundabouts in Addis Ababa, Ethiopia, representing about 56% of such roundabouts in Addis Ababa. To account for spatial correlation resulting from multiple observations at a roundabout, both the random effect Poisson (REP) and random effect negative binomial (RENB) regression models were estimated. Model goodness-of-fit statistics revealed a marginally superior fit of the REP model to the data compared with the RENB model. Pedestrian crossing volume and the product of traffic volumes along major and minor roads had significant and positive associations with pedestrian crashes at roundabouts. The presence of a public transport (bus or taxi) terminal beside a roundabout was associated with increased pedestrian crashes. Although the maximum gradient of an approach road was negatively associated with pedestrian safety, the provision of a raised median along an approach appeared to increase pedestrian safety at roundabouts. Remedial measures were identified for combating pedestrian safety problems at roundabouts in the context of a developing country.
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Vinayaraj, V. S., and Vedagiri Perumal. "Safety evaluation of urban roundabouts in India: a safety performance function-based approach." Traffic Safety Research 3 (October 22, 2022): 000015. http://dx.doi.org/10.55329/bylj4120.
Full textAbstract:
There is a lack of comprehensive research in roundabout safety under non-lane-based traffic conditions, mainly due to the absence of relevant crash data and effective tools for safety evaluation. Safety Performance Function (SPF) is a suitable tool for providing valuable information related to factors which can potentially contribute to the likelihood of increasing traffic crashes. Currently, very limited studies are available to explain the usefulness of SPF in the vicinity of roundabouts, especially at non-lane-based traffic conditions. This study aims to develop an SPF model for assessing the safety evaluation at roundabouts as a whole (intersection level) and the approach level. Data corresponding to crashes in nineteen roundabouts with different geometric and traffic characteristics was used for model formulation. Crash data for five years (2015–2019) was obtained from the State Crime Records Bureau. An SPF model was developed using a negative binomial model with a log-link function based on the number of crashes, traffic characteristics, and geometry characteristics of the roundabouts. The proportion of powered two-wheelers, percentage of heavy vehicles, entry-angle, and weaving-length were all significantly related with higher crash occurrences at roundabouts, according to the findings. In contrast, the number of circulatory lanes, inscribed circle diameter, and presence of road lane marking were negatively associated with the increased crash occurrences at the roundabout vicinity. In addition to this, the overall crash rate significantly varies across roundabout sections due to the asymmetric effects of geometric and traffic characteristics. The developed SPF would best explain the relationship between geometric and traffic characteristics and the crash occurrence rate in non-lane traffic conditions. The findings of this study support the need to relook at design parameters for better movement at the roundabouts, thereby improving the existing facilities to enhance road users' safety, especially in developing countries. The proposed SPF tool would help engineers examine the safety of roundabouts in terms of design adequacy, quantifying the risk factors, and future crash predictions.
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Giuffrè, Tullio, Anna Granà, and Salvatore Trubia. "Safety Evaluation of Turbo-Roundabouts with and without Internal Traffic Separations Considering Autonomous Vehicles Operation." Sustainability 13, no. 16 (August 6, 2021): 8810. http://dx.doi.org/10.3390/su13168810.
Full textAbstract:
The paper presents a microsimulation approach for assessing the safety performance of turbo-roundabouts where Cooperative Autonomous Vehicles “CAVs” have been introduced into the traffic mix alongside conventional vehicles “CVs”. Based on the analysis of vehicle trajectories from VISSIM and subsequent analysis of traffic conflicts through the Surrogate Safety Assessment Model (SSAM), the research aims to evaluate the safety benefits of turbo-roundabouts where the lanes are physically separated by raised curbs, compared to roundabouts without such curbs. The paper will then describe the methodological path followed to build VISSIM models of turbo-roundabouts with and without raised curbs in order to calibrate the simulation models and estimate the potential conflicts when a higher percentage of CAVs are introduced into the traffic mix. A criterion has been also proposed for setting properly the principal SSAM filters. The results confirmed both higher safety levels for turbo-roundabouts equipped with raised lane dividers compared to turbo-roundabout solutions without curbs, and better safety conditions under the traffic mix of CVs and CAVs. Therefore, it follows that, in absence of crash data including CAVs, the surrogate measures of safety are the only approach in which the safety performance of any roundabout or road entity can be evaluated.
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Tan, Tana, Lachlan Lee-Archer, Thomas Mason, Jey Parthiban, and Tom Beer. "Bicycle-Friendly Roundabouts: A Case-Study." Journal of the Australasian College of Road Safety 30, no. 4 (November 5, 2019): 67–70. http://dx.doi.org/10.33492/jacrs-d-19-00257.
Full textAbstract:
Roundabouts constrain speeds and impact angles for vehicles as they approach. Therefore, they are considered to be a ‘Safe System’ solution for intersections. Though roundabouts are a positive road safety treatment for cars they do not show as dramatic a reduction in road trauma for bicyclists. New Zealand crash data for 2001-2011, found almost 28% of injury crashes at roundabouts involve cyclists, while at priority-controlled intersections and signalised intersections the proportions are 8% and 5.5% respectively. VicRoads specifies technical guidance in relation to road safety treatments at roundabouts specifically targeted for the protection of cyclists and pedestrians. In 2018 this guidance was used to design and build two cycle-friendly protected roundabouts in Moray St, South Melbourne, as part of the Metro Tunnel Project. The project upgraded the Moray Street bicycle path to provide cyclists with a safe path in the north-south route and raised pedestrian crossings at all branches of the roundabout during Metro Tunnel works on St Kilda Road. Safe System Solutions Pty Ltd evaluated the performance and found a moderate utilisation rate of cyclists on the dedicated bicycle lanes and a high utilisation rate of pedestrians using raised crossings. The evaluation also found no significant issues with near-crashes for bicycle-and-pedestrian and bicycle-and-vehicle interaction. There were no significant problems with vehicle drivers using the protected roundabout. However, it was noted that when pedestrians are crossing at the raised crossings then vehicles would sometimes stop in the middle of the roundabout thus blocking traffic.
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MACIOSZEK, Elżbieta. "ROUNDABOUTS AS AESTHETIC ROAD SOLUTIONS FOR ORGANIZING LANDSCAPES." Scientific Journal of Silesian University of Technology. Series Transport 115 (June 30, 2022): 53–62. http://dx.doi.org/10.20858/sjsutst.2022.115.4.
Full textAbstract:
In the transportation systems are different types of intersections. Among them, roundabouts are considered the safest solution. The application of roundabouts is conditioned by many factors. One of them borders on area development. Roundabouts, among others, are localized in important city places, thus serve as a landmark in the city or are localized on the boundaries of areas with different communication functions, thus constituting an organizational landscape feature. Sometimes, they diversify the space of a street or close the perspective of a monotonous street. Hence, beyond the basic functions, roundabouts with the appropriate central island arrangements can also play the function of organizing the architecture of the local area. The ways and possibilities of roundabout central island arrangements are presented in this article. An interesting central island arrangement shows that roundabouts play an esthetic and organizing landscaping role.
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Flannery, Aimee, and Tapan Datta. "Operational Performance Measures of American Roundabouts." Transportation Research Record: Journal of the Transportation Research Board 1572, no. 1 (January 1997): 68–75. http://dx.doi.org/10.3141/1572-09.
Full textAbstract:
The introduction of a new form of at-grade intersection control in the United States, termed a roundabout, has left many researchers and practitioners puzzled about their performance level. Many researchers and practitioners have looked to foreign design and operational manuals for guidance. Although the methods contained in these manuals have been implemented in their respective countries, no one is certain how they will transfer to conditions in the United States. Considering that driver characteristics are a major contributor to operational performance, these methods may not accurately depict the performance level of roundabouts with American drivers. Driver characteristics, in relation to operational performance, of four single-lane roundabouts located in the United States are described. The same driver characteristics are compared with findings in Australia under similar conditions; in addition, the probability density function for gap acceptance is derived. American drivers do not always react the same as Australian drivers under similar conditions. However, use of the Australian methods is, in most cases, more conservative and therefore should not overpredict the capacity and performance of roundabouts in the United States. The probability density function for gap acceptance at roundabouts was similar in shape and slope to that of two-way stop control. However, comparison of the gap-acceptance values of right-turning vehicles at two-way stop control with those at a roundabout indicates that drivers at roundabouts accept smaller gaps in the traffic stream on entry. This leads to the conclusion that roundabouts should perform better than two-way or all-way stop-controlled intersections under most conditions. The question remains: When do roundabouts function better than traffic signals?
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García Cuenca, Laura, Enrique Puertas, Javier Fernandez Andrés, and Nourdine Aliane. "Autonomous Driving in Roundabout Maneuvers Using Reinforcement Learning with Q-Learning." Electronics 8, no. 12 (December 13, 2019): 1536. http://dx.doi.org/10.3390/electronics8121536.
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Navigating roundabouts is a complex driving scenario for both manual and autonomous vehicles. This paper proposes an approach based on the use of the Q-learning algorithm to train an autonomous vehicle agent to learn how to appropriately navigate roundabouts. The proposed learning algorithm is implemented using the CARLA simulation environment. Several simulations are performed to train the algorithm in two scenarios: navigating a roundabout with and without surrounding traffic. The results illustrate that the Q-learning-algorithm-based vehicle agent is able to learn smooth and efficient driving to perform maneuvers within roundabouts.
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Du, Canyi, Xinfa Qiu, Feng Li, and Ming Cai. "A simulation of traffic noise emissions at a roundabout based on a cellular automaton model." Acta Acustica 5 (2021): 42. http://dx.doi.org/10.1051/aacus/2021037.
Full textAbstract:
The calculation and evaluation of traffic noise is an important task in urban road design. Roundabouts are a common form of urban road intersection. The complexity of traffic operations makes the calculation of traffic noise near a roundabout challenging. To explore traffic noise at roundabouts, a cellular automaton traffic flow model for a two-lane roundabout is established. Based on this model, a dynamic simulation method for traffic noise at roundabouts is proposed. The traffic operation and noise emissions at a roundabout are simulated. The vehicle speed distribution and traffic noise distribution at the roundabout are analysed, and the relationship between the traffic volume and sound power level of the cells is discussed. Finally, the proposed method is compared with existing traffic noise models, and the accuracy and efficiency of the proposed method are verified. The results of this paper show that the speed distribution and noise emission distribution at the roundabout are not uniform. When the traffic volume increases to saturation, the noise emission on the ring road will not keep increasing, and the sound power level of the cells on the inner ring is approximately 2 dBA higher than that of the outer ring. The methods and results in this paper may be valuable for road traffic design and noise control.
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Du, Canyi, Xinfa Qiu, Feng Li, and Ming Cai. "A simulation of traffic noise emissions at a roundabout based on a cellular automaton model." Acta Acustica 5 (2021): 42. http://dx.doi.org/10.1051/aacus/2021037.
Full textAbstract:
The calculation and evaluation of traffic noise is an important task in urban road design. Roundabouts are a common form of urban road intersection. The complexity of traffic operations makes the calculation of traffic noise near a roundabout challenging. To explore traffic noise at roundabouts, a cellular automaton traffic flow model for a two-lane roundabout is established. Based on this model, a dynamic simulation method for traffic noise at roundabouts is proposed. The traffic operation and noise emissions at a roundabout are simulated. The vehicle speed distribution and traffic noise distribution at the roundabout are analysed, and the relationship between the traffic volume and sound power level of the cells is discussed. Finally, the proposed method is compared with existing traffic noise models, and the accuracy and efficiency of the proposed method are verified. The results of this paper show that the speed distribution and noise emission distribution at the roundabout are not uniform. When the traffic volume increases to saturation, the noise emission on the ring road will not keep increasing, and the sound power level of the cells on the inner ring is approximately 2 dBA higher than that of the outer ring. The methods and results in this paper may be valuable for road traffic design and noise control.
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Almoarawi, Mohammad, and Essam Dabbour. "Predicting Operating Speeds at Urban Multilane Roundabouts in Abu Dhabi, United Arab Emirates." Journal of Advanced Transportation 2018 (May 30, 2018): 1–10. http://dx.doi.org/10.1155/2018/8363064.
Full textAbstract:
There are more than 460 multilane roundabouts located in Abu Dhabi, the capital city of the United Arab Emirates, and its surrounding areas. Most of those roundabouts have three entry/circulatory/exit lanes with large radii, which resulted in the majority of drivers exceeding the speed limits for those roundabouts. Those excessive operating speeds, along with lack of drivers’ awareness of the proper rules of driving at roundabouts, have resulted in increased collision frequencies at Abu Dhabi roundabouts. In this paper, operating speeds were measured at 12 roundabouts in Abu Dhabi and those collected speed observations were used to calibrate regression models to predict the 85th percentile operating speeds at roundabouts in Abu Dhabi. Predicting operating speed at a roundabout, during its design stage, is necessary to ensure that the expected operating speed and capacity will meet the design expectations. Three models were calibrated to predict the entry, circulating, and exit speeds, respectively. The calibrated models were validated with data not used in calibration and they were found to be stable and robust. The findings of this research study will help engineers when designing new roundabouts in Abu Dhabi or other cities with similar characteristics. This research study also provides a methodological framework for other researchers when conducting similar speed studies for roundabouts in other cities or metropolitan areas around the world.
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Abbood, Abdul Kareem Naji, and Aboothar Abdul Hussein Hamzah Al-Tufail. "Evaluation and Improvement of Roundabouts in CBD Area at Al-Hilla City." Journal of University of Babylon for Engineering Sciences 26, no. 7 (July 2, 2018): 72–86. http://dx.doi.org/10.29196/jubes.v26i7.1488.
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In the present-day, congestion considers one of the biggest problems experienced by urban areas. This congestion led to form the conflicting movements at intersections, merging, roundabouts, etc. The objective of this study is to investigate the traffic congestion problem at the two selected roundabouts at CBD area in Hilla city. Roundabouts consider safer than the conventional intersections, but it has less capacity than corresponding intersections. In Iraq, several roundabouts were built in the last decade to improve the traffic performance. However, most of these roundabouts are unable to accommodate the rapid growth in traffic volumes and suffer from a serious issue in congestion. Therefore, this study aims to evaluate these roundabouts. The VISSIM simulation software has been used to perform the evaluation analysis for these selected roundabouts. Then, field data have been collected by using two video cameras that installed by using a fabricated equipment. The process of collecting data has lasted for 8 hours at each roundabout. And then, this field data has been used to calibrate the simulation model (VISSIM). After making the required calibration and validation for the simulation model, the developed model was depended to perform the evaluation and find the suitable solution to solve the traffic congestion at these roundabouts.
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Li, X., and W. Zhang. "AUTOMATIC OBJECT-ORIENTED ROUNDABOUTS EXTRCTION FROM HIGH RESOLUTION MULTISPECTRAL IMAGES." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W7 (September 13, 2017): 779–84. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w7-779-2017.
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Road roundabouts, a typical class of road facilities to avoid collision, are generally not directed extracted in existing road extraction methods. This paper presents a novel four-step approach for automatic vegetated roundabout extractions from high resolution multispectral satellite images, which combines object-oriented extraction, Support Vector Machine (SVM) classification and spatial relationship estimation. Firstly, after proper preconditioning, the vegetated roundabouts are extracted by object-oriented extract algorithm in ENVI with rules that simultaneously taking area, roundness and vegetation index (NDVI) into consideration. After a certain number of experiments, the set of three items’ thresholds can be found, which may stand as the general rules for vegetated roundabouts extraction in similar conditions. Next, the roads are classified using Support Vector Machine (SVM) and the outputs are several band shaped polygons. Then, the holes in road polygons will be detected by examining the topological relation in ArcGIS. Lastly, since the margin of extracted roundabout and the biggest detected hole may not strictly coincide, by comparing the distance between central points of both the extracted roundabout and the hole with the threshold, convincing determination can be made. The proposed automatic approach has been proved to have very high production accuracy that all above 85 % in each case of the test set, which is good enough for automatic vegetated roundabouts extraction from high resolution remote sensing images without manual interpretation.
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Al-Ghandour, Majed. "Simulation Study of Truck Traffic at Single-Lane Roundabouts with and without Slip Lanes." Transportation Research Record: Journal of the Transportation Research Board 2517, no. 1 (January 2015): 80–86. http://dx.doi.org/10.3141/2517-09.
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As transportation planners and engineers design useful and effective roundabouts, these professionals are challenged by the need to accommodate safely truck traffic and high truck volumes in particular. Delay is a major challenge with truck traffic, especially with returning left-turning trucks. The delay performance of single-lane roundabouts with an adjacent slip lane for right turns was considered under various truck traffic percentages and two slip lane exit types (free flow and yield). A microsimulation assessment compared four percentages of right-turn truck traffic: 0% (no trucks), 5%, 45%, and 80%. Results indicate that the average delay of a roundabout with a slip lane under various truck traffic percentages is a nonlinear relationship with slip lane volumes and is sensitive to changes in truck traffic percentages before oversaturation is reached. As expected, results indicate that a free-flow slip lane exit type significantly reduces total average delay in roundabouts compared with having no slip lane with truck traffic. Yield slip lane exit types also reduced total average delay from truck traffic in roundabouts, but to a lesser degree than free-flow slip lane exit types. At higher truck traffic volumes, overall average roundabout delay decreased 15% (estimated VISSIM 95% confidence interval of reduction estimated between —16% and —2%) with a free-flow slip lane exit type. Finally, returning left-turn trucks increased total roundabout average delay significantly, by 64%.
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Gavulová, Andrea, and Marek Drličiak. "Capacity Evaluation of Roundabouts in Slovakia." Transport and Telecommunication Journal 13, no. 1 (January 1, 2012): 1–10. http://dx.doi.org/10.2478/v10244-012-0001-0.
Full textAbstract:
Capacity Evaluation of Roundabouts in Slovakia Two technical regulations for capacity estimation of roundabouts are valid in the Slovak Republic at the present time. Each of these regulations is based on a different theory of capacity estimation which affects the outcome of the capacity of roundabouts and their evaluation. The capacity of various roundabouts was estimated according to both methods in the previous analysis made at our department [3] and in some cases different results of the evaluation were achieved. The question is: which one of the mentioned theories better reflects a real capacity of the roundabout? For this reason some of the existing roundabouts in the town Žilina were selected and they were evaluated according to both methods and a micro simulation using PTV Vissim software. The geometrical parameters of roundabout, real driving behaviour (speed, proportions, acceleration, etc.) and also pedestrian behaviour were taken into account in the microscopic models. The first assumption for capacity evaluation by a microscopic traffic model is a calibration process which is based on traffic surveys results. Thus created models allow several capacity analyses during the peak traffic loading. Then, the results of micro-simulation can be compared with the capacity evaluation according to the technical regulations. The article deals with creation and calibration of microscopic traffic models and with the mentioned comparing of results.
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Novák, Jan, Jiří Ambros, and Jindřich Frič. "How Roundabout Entry Design Parameters Influence Safety." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 34 (June 8, 2018): 73–84. http://dx.doi.org/10.1177/0361198118776159.
Full textAbstract:
Roundabouts are considered the safest intersection design; however, the safety effect may not be satisfactory at each specific roundabout. This is true especially in countries where roundabout design is a relatively new concept, such as in the Czech Republic. Specifically, most Czech roundabout crashes were found to occur on entries. This motivated the presented study to investigate how entry design parameters influence safety on Czech roundabouts and, if possible, use the findings to update current Czech roundabout design guidelines. To this end, the study comprised three analyses: crash-based safety performance functions, speed analysis, and finally safety performance functions which incorporated speed. All three analyses proved that entry design parameters have a statistically significant influence on safety, in terms of crash frequency, severity and speeds. Given the study objective, this fact should be considered in Czech roundabout design guidelines.
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Shaaban, Khaled, and Hassan Hamad. "Critical Gap Comparison between One-, Two-, and Three-Lane Roundabouts in Qatar." Sustainability 12, no. 10 (May 21, 2020): 4232. http://dx.doi.org/10.3390/su12104232.
Full textAbstract:
A critical gap value of a roundabout is mainly affected by the interactions between the circulating vehicles and vehicles entering the roundabout. These interactions are impacted by many factors, including the number of circulating lanes, the aggressiveness of local drivers, vehicle types, and the number of approaching lanes. Therefore, it is essential to locally investigate critical gap values before conducting any studies to improve capacity and delay at roundabouts. The purpose of this study is to measure and compare the critical gap values for different types of roundabouts in Qatar. More than 10,000 measurements were collected. The results showed that the critical gap values were 2.24 s, 2.55 s, and 2.40 s for the one-, two-, and three-lane roundabouts, respectively. These values are also quite low when compared to values calculated in other countries, which can be an indication of driver aggressiveness and risky behavior. The study is one of the first efforts to compare three types of roundabouts and to understand the difference in operation between them in this region. The results of this study can help engineers, planners, and public agencies to plan, study, and design similar facilities.
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Giuffrè, Orazio, Anna Granà, Sergio Marino, and Fabio Galatioto. "MICROSIMULATION-BASED PASSENGER CAR EQUIVALENTS FOR HEAVY VEHICLES DRIVING TURBO-ROUNDABOUTS." TRANSPORT 31, no. 2 (June 28, 2016): 295–303. http://dx.doi.org/10.3846/16484142.2016.1193053.
Full textAbstract:
Due to its geometric design, turbo-roundabouts impose greatest constraints to the vehicular trajectories; by consequence, one can expect a more unfavourable impact of heavy vehicles on the traffic conditions than on other types of roundabouts. The present paper addresses the question of how to estimate Passenger Car Equivalents (PCEs) for heavy vehicles driving turbo-roundabouts. The microsimulation approach used revealed as a useful tool for evaluating the variation of quality of traffic in presence of mixed fleets (different percentages of heavy vehicles). Based on the output of multiple runs of several scenarios simulation, capacity functions for each entry lane of the turbo-roundabout were developed and variability of the PCEs for heavy vehicles were calculated by comparing results for a fleet of passenger cars only with those of the mixed fleet scenarios. Results show a dependence of PCEs for heavy vehicles on operational conditions, which characterise the turbo-roundabout. Assuming the values of PCEs for roundabouts provided by the 2010 Highway Capacity Manual (HCM), depending on entering manoeuvring underestimation and overestimation of the effect of heavy vehicles on the quality of traffic conditions have been found.
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WANG, RUILI, and H. J. RUSKIN. "MODELLING TRAFFIC FLOW AT MULTI-LANE URBAN ROUNDABOUTS." International Journal of Modern Physics C 17, no. 05 (May 2006): 693–710. http://dx.doi.org/10.1142/s0129183106008777.
Full textAbstract:
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 and congestion. The operations of two- and three-lane roundabouts are compared in terms of throughputs. Vehicle movements in this paper relate to left-side driving, such as found in Ireland, New Zealand and the UK. However, results are generally applicable to the countries where the give-way rule is applied.