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Roundabouts Performance in Road Transport Networks—Future Challenges, Problems and Issues

A special issue of Sustainability (ISSN 2071-1050). This special issue belongs to the section "Sustainable Transportation".

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 24455

Special Issue Editors


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Guest Editor
Department of Transport Systems, Traffic Engineering and Logistics, Faculty of Transport and Aviation Engineering, Silesian University of Technology, Krasińskiego 8 Street, 40-019 Katowice, Poland
Interests: road traffic engineering; road and intersections capacity analysis; measurements; traffic modeling; research and traffic flow analysis; transport infrastructure; functional analysis; transport systems and processes modeling; transportation engineering
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Guest Editor
Faculty of Civil Engineering, Transportation Engineering and Architecture, University of Maribor, Smetanova 17, 2000 Maribor, Slovenia
Interests: sustainable safe road infrastructure design; with particular focus on intersections; interchanges; roundabouts; vulnerable road users

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Guest Editor
Faculty of Engineering and Architecture, University of Enna Kore, Viale della Cooperazione, 94100 Enna, Italy
Interests: road safety evaluation; road design; connected automated vehicle operation; transport infrastructure; traffic operation modeling; statistical analysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Many different layouts and sizes can be used to design modern roundabouts. The type of roundabout is determined by various factors, such as space availability, traffic volume, expected and-users, location, etc. Roundabouts are often used to improve traffic safety and capacity in urban and rural areas and can also be employed as a measure for traffic calming instead of signal-controlled intersections.

This Special Issue will consist of papers describing the synthesis of current theory and practice of planning, design, operation, and safety of modern roundabouts, with special attention on future challenges and will be of interest to scientists dealing with roundabouts problems and issues and generally involved in road traffic engineering as well as design, traffic, and maintenance engineers. Other major areas of interest with regard to roundabouts include but are not limited to:

  • Efficiency evaluation;
  • Traffic capacities and delays;
  • Issues related to pedestrians, bicyclists, and visually impaired users;
  • Costs and location criteria;
  • Road traffic measurements, data analysis;
  • Traffic flow modeling;
  • Signing and pavement markings;
  • Signalized roundabouts;
  • Experimental analysis for roundabouts;
  • Autonomous vehicles on roundabouts;
  • Driver behavior patterns on roundabouts;
  • Conflicts at roundabouts.

Prof. Elżbieta Macioszek
Prof. Anna Grana
Prof. Dr. Tomaž Tollazzi
Dr. Tullio Giuffrè
Guests Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sustainability is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • road traffic engineering
  • road transport network
  • modern roundabouts

Published Papers (11 papers)

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Research

21 pages, 4408 KiB  
Article
Roundabout Trajectory Planning: Integrating Human Driving Models for Autonomous Vehicles
by Salvatore Leonardi and Natalia Distefano
Sustainability 2023, 15(23), 16288; https://doi.org/10.3390/su152316288 - 24 Nov 2023
Viewed by 833
Abstract
This research investigates the utilization of human driving models in autonomous vehicles, particularly in scenarios with minimal or no interactions with other vehicles. Human driving models provide valuable insights into driver behavior and play a crucial role in shaping the behavior of autonomous [...] Read more.
This research investigates the utilization of human driving models in autonomous vehicles, particularly in scenarios with minimal or no interactions with other vehicles. Human driving models provide valuable insights into driver behavior and play a crucial role in shaping the behavior of autonomous vehicles, enhancing their performance and user experience. The primary focus of this study is the creation of a planning model for autonomous vehicles when navigating roundabouts in the absence of traffic. This model seeks to emulate human driving behavior, ensuring predictability, safety, the optimization of traffic flow, and adaptation to various roundabout geometries. To achieve this, the research introduces a trajectory model that takes into account geometric attributes and speed variations within roundabouts. The model is calibrated using empirical data and generalizes parameters through statistical regression methodologies. In particular, speed profile modeling is evaluated for its consistency in creating plans that faithfully replicate human driving behavior in roundabouts. While the study presents a promising approach, it acknowledges limitations related to the model’s reliance on geometric attributes and its inability to account for external factors like weather conditions. This research underscores the importance of bridging the gap between theoretical research and practical application, with the aim of enhancing safety and the overall user experience in real-world driving scenarios. Full article
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24 pages, 15295 KiB  
Article
Design of Turbo-Roundabouts Based on the Rules of Vehicle Movement Geometry on Curvilinear Approaches
by Alicja Barbara Sołowczuk and Weronika Benedysiuk
Sustainability 2023, 15(18), 13882; https://doi.org/10.3390/su151813882 - 18 Sep 2023
Cited by 1 | Viewed by 827
Abstract
The construction of turbo-roundabouts is an increasingly frequent choice when it comes to improving flow capacity and traffic safety at road intersections. The existing design guidelines, as a rule, give parameters for turbo-roundabouts with approaches set at right angles to each other. The [...] Read more.
The construction of turbo-roundabouts is an increasingly frequent choice when it comes to improving flow capacity and traffic safety at road intersections. The existing design guidelines, as a rule, give parameters for turbo-roundabouts with approaches set at right angles to each other. The article presents turbo-roundabout design methods, taking into account swept path analyses of the chosen design vehicles when the approach legs are curvilinear and oriented to each other at a non-right angle. Based on the analysis of three different design vehicles, it was proven that their swept paths have a major influence on the geometrical parameters of the roundabout and, consequently, on the land take area, i.e., they can significantly impact the project’s construction costs. In the case of curvilinear approaches, which are oriented to each other at a non-right angle, it is impossible to impose on the designer specific values of the circulatory lane widths and the entry and exit curve radii as they depend primarily on the chosen design vehicle. The aim of the article was to demonstrate that in the case of the curvilinear approach on the Basic type turbo-roundabout, the design process should include the swept path analysis for the chosen design vehicle for each of the approaches. This should lead to the design of wider swept paths and higher curve lane divider entry and exit radii. Full article
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28 pages, 23495 KiB  
Article
Design Study for the Construction of Turbo Roundabouts under Constrained Site Conditions
by Alicja Sołowczuk and Stanisław Majer
Sustainability 2023, 15(17), 13220; https://doi.org/10.3390/su151713220 - 3 Sep 2023
Viewed by 1207
Abstract
Turbo-roundabouts are one of the most frequently recommended road junction design options when it comes to increasing traffic capacity and traffic safety. This is in particular true of suburban areas, with dominant traffic flow on the main road and moderate traffic flow on [...] Read more.
Turbo-roundabouts are one of the most frequently recommended road junction design options when it comes to increasing traffic capacity and traffic safety. This is in particular true of suburban areas, with dominant traffic flow on the main road and moderate traffic flow on the side road. Other intersections handling local traffic and considerably constricting the availability of space are usually located in the vicinity of such intersections. Another factor contributing to the limited availability of land for construction in these locations is the presence of surrounding residential housing. Then, choosing the suitable turbo-roundabout type becomes the main issue. The article presents a case study for the selection of a type of turbo roundabout under the conditions of considerably constricted land availability based on the analysis of the provision of a swept path for the chosen design vehicles. The article considers the standard egg-type turbo-roundabouts, “look-a-like” type turbo-roundabouts, non-standard “flattened” turbo-roundabouts and ellipse-based roundabouts, with non-standard geometries of the truck apron and central island. For each of the analysed roundabout types, setting-out methods were described in detail, allowing the designer to quickly select a type of roundabout suitable for the specific constrained site conditions. This article analyses the applicability of non-standard turbo roundabouts for three area types: LUDA low urbanisation degree area, BA built-up area and CDA highly commercially developed area along the side road, wherever standard roundabouts are not practicable due to constraints imposed by existing buildings, canals or any other obstacles found at the project site. Full article
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19 pages, 10057 KiB  
Article
A Conflict-Based Safety Diagnosis of SCI Roundabouts Using a Surrogate Safety Measure Model
by Mehrzad Hasanvand, Amir Saman Abdollahzadeh Nasiri, Omid Rahmani, Khaled Shaaban and Hossein Samadi
Sustainability 2023, 15(17), 13166; https://doi.org/10.3390/su151713166 - 1 Sep 2023
Viewed by 1177
Abstract
Recently, the surrogate safety assessment model has been considered for the safety performance analysis of roundabouts. This model can perform a detailed analysis of conflicts based on the trajectory data of vehicles inside the roundabout. The Separated Central Island (SCI) roundabout, as one [...] Read more.
Recently, the surrogate safety assessment model has been considered for the safety performance analysis of roundabouts. This model can perform a detailed analysis of conflicts based on the trajectory data of vehicles inside the roundabout. The Separated Central Island (SCI) roundabout, as one of the roundabouts with distinct geometrical characteristics, holds the potential for safety evaluation using the conflict-based method. Therefore, in this study, a safety diagnosis of an SCI roundabout was conducted for the first time. In this study, a safety diagnosis procedure for SCI roundabout was first defined; for this purpose, vehicle trajectory data were obtained using an Unnamed Aerial Vehicle (UAV) and then entered into Surrogate Safety Measure Model software (SSAM 3.0). A case study was conducted on the only SCI roundabout in Iran, located in Mashhad. The parameters of Time-to-Collision (TTC), maximum speed difference of two vehicles involved in a collision (MaxΔV), and maximum speed of vehicles in collision (MaxS) were utilized to determine the type and severity of conflicts and risk analysis. The results of roundabout risk analysis showed that the severity level of conflicts is mainly of the injury type and that the lowest severity of conflicts is related to fatality. In addition, the highest frequency of injury conflicts is associated with lane-change conflict and the lowest frequency is linked to rear-end conflict. The highest and lowest frequency of damage conflicts are related to crossing and lane-change conflicts, respectively. After overall risk scoring, the severity level of conflicts is mainly related to injury type and the lowest severity of conflicts is associated with fatality; 31% of the total conflicts obtained are of the damaging type, and 69% are of the injury type. Finally, comparing the results of the conflict data with the 8-year crash data in such roundabouts confirms that in the absence of crash data in such roundabouts traffic engineers can use the roundabout analysis based on this study to predict the safety situation of such roundabouts before implementing engineering processes. Full article
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17 pages, 3293 KiB  
Article
Development of Artificial Intelligence Based Safety Performance Measures for Urban Roundabouts
by Fayez Alanazi, Ibrahim Khalil Umar, Sadi Ibrahim Haruna, Mahmoud El-Kady and Abdelhalim Azam
Sustainability 2023, 15(14), 11429; https://doi.org/10.3390/su151411429 - 23 Jul 2023
Viewed by 931
Abstract
A reliable model for predicting crash frequency at roundabouts is an essential tool for evaluating the safety measures of a roundabout. This study developed a hybrid PSO-ANN model by optimizing the modeling parameters of the classical artificial neural network (ANN) model with the [...] Read more.
A reliable model for predicting crash frequency at roundabouts is an essential tool for evaluating the safety measures of a roundabout. This study developed a hybrid PSO-ANN model by optimizing the modeling parameters of the classical artificial neural network (ANN) model with the particle swarm optimization algorithm (PSO). The performance accuracy of the models was evaluated using the mean absolute error (MAE), root mean square error (RMSE), and determination coefficients (DC). The PSO-ANN model predicted the crash frequency with very good accuracy at the testing stage (DC = 0.7935). The hybrid model could improve the performance of the classical ANN model by up to 23.3% in the training stage and 16.9% in the testing stage. In addition to the statistical measures, graphical approaches (scatter and violin plots) were also used for evaluating the models’ accuracy. Both statistical and graphical evaluation techniques prove the reliability and accuracy of the proposed hybrid model in predicting the crash frequency at roundabouts. Full article
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14 pages, 1498 KiB  
Article
Impact of Autonomous Vehicles on Roundabout Capacity
by Othmane Boualam, Attila Borsos, Csaba Koren and Viktor Nagy
Sustainability 2022, 14(4), 2203; https://doi.org/10.3390/su14042203 - 15 Feb 2022
Cited by 13 | Viewed by 2889
Abstract
Studying the impact of AVs on our road infrastructure offers a lot of potential in the transportation domain; one of these issues is how capacity will be affected. This paper presents a contribution to this research area by investigating the impact of AVs [...] Read more.
Studying the impact of AVs on our road infrastructure offers a lot of potential in the transportation domain; one of these issues is how capacity will be affected. This paper presents a contribution to this research area by investigating the impact of AVs on the capacity of single-lane roundabouts using a microsimulation model. For the development of the model, a roundabout situated in Győr (Hungary) was selected and field data on the roundabout geometric characteristics as well as traffic volumes were used. Simulations using Vissim were run for various scenarios based on varying input traffic volumes and market penetration rates of AVs to assess queue lengths. The highway capacity manual (HCM) roundabout model was used to estimate the capacity of the existing roundabout. Values of follow-up times and critical gaps were set to decreasing as the penetration rate of AVs increases. The results demonstrated that 20% and 40% AVs in the flow would increase leg capacities by about 10% and 20%, respectively. Furthermore, a reduction in excessive queue lengths was estimated and capacities and queue lengths were calculated by legs. It was found that these are highly influenced by the distribution of flows among legs, and the share of flows in various directions. Full article
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14 pages, 334851 KiB  
Article
Safety Evaluation of Flower Roundabout Considering Autonomous Vehicles Operation
by Alessandro Severino, Giuseppina Pappalardo, Salvatore Curto, Salvatore Trubia and Isaac Oyeyemi Olayode
Sustainability 2021, 13(18), 10120; https://doi.org/10.3390/su131810120 - 9 Sep 2021
Cited by 32 | Viewed by 2855
Abstract
With the significant technological growth that affected autonomous vehicles in the last decade, several consequences occurred as: human factor exclusion, entry and exit manoeuvres precision from roundabouts, and headway reduction. In this paper, it was carried out a microsimulation approach study that aims [...] Read more.
With the significant technological growth that affected autonomous vehicles in the last decade, several consequences occurred as: human factor exclusion, entry and exit manoeuvres precision from roundabouts, and headway reduction. In this paper, it was carried out a microsimulation approach study that aims to evaluate benefits in terms of safety obtained with flower roundabouts in a scenario where traffic is characterized by conventional vehicles “CVs” and Connected Autonomous Vehicles “CAVs”. This study focused on the evaluation of CAVs and CVs operation with the presence of the so called “weak users” or rather, pedestrians and bikes. Then, simulated scenarios were characterized by the presence of zebra-crossings in main roads, positioned at 20 m from circulatory carriageway edges. Micro simulation choice is due to the absence of survey data collection because the presence of CAVs in ordinary traffic is still minimal. The micro simulation was carried out through VISSIM, so it was operated with a specific methodological path, consisting, in the application, of O–D matrix based on real cases, in order to achieve an assessment of potential conflicts in relation with the increase in CAVs. Simulation results showed that higher safety levels were achieved for special cases of O–D distribution and with CAVs present. Finally, considering crash absence in results related to CAVs presence, safety interventions of such roundabout types have to be thorough. There were 10 O/D matrices analysed through VISSIM considering parameters as: average tail length, maximum tail length, average speed, vehicles, and number of stops quantity. As reported in the conclusion section, O/D matrices that showed minimum conflicts and maximum dynamic performances were identified. Full article
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14 pages, 2647 KiB  
Article
Safety Evaluation of Turbo-Roundabouts with and without Internal Traffic Separations Considering Autonomous Vehicles Operation
by Tullio Giuffrè, Anna Granà and Salvatore Trubia
Sustainability 2021, 13(16), 8810; https://doi.org/10.3390/su13168810 - 6 Aug 2021
Cited by 12 | Viewed by 2165
Abstract
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 [...] Read more.
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. Full article
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15 pages, 5029 KiB  
Article
Data-Driven Scenario Specification for AV–VRU Interactions at Urban Roundabouts
by Andreas Keler, Patrick Malcolm, Georgios Grigoropoulos, Seyed Abdollah Hosseini, Heather Kaths, Fritz Busch and Klaus Bogenberger
Sustainability 2021, 13(15), 8281; https://doi.org/10.3390/su13158281 - 24 Jul 2021
Cited by 6 | Viewed by 2078
Abstract
Detailed specifications of urban traffic from different perspectives and scales are crucial for understanding and predicting traffic situations from the view of an autonomous vehicle (AV). We suggest a data-driven specification scheme for maneuvers at different design elements of the built infrastructure and [...] Read more.
Detailed specifications of urban traffic from different perspectives and scales are crucial for understanding and predicting traffic situations from the view of an autonomous vehicle (AV). We suggest a data-driven specification scheme for maneuvers at different design elements of the built infrastructure and focus on urban roundabouts in Germany. Based on real observations, we define classes of maneuvers, interactions and driving strategies for cyclists, pedestrians and motorized vehicles and define a matrix for merging different maneuvers, resulting in more complex interactions. The sequences of these interactions, which partially consist of explicit communications, are extracted from real observations and adapted into microscopic traffic flow simulations. The simulated maneuver sequences are then visualized in 3D environments and experienced by bicycle simulator test subjects. Using trajectory segments (in fictional space) from two conducted simulator studies, we relate the recorded movement patterns of test subjects with observed cyclists in reality. Full article
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14 pages, 1231 KiB  
Article
Modeling the Influence of Roundabout Deflection on Its Efficiency as a Noise Abatement Measure
by Saša Ahac, Maja Ahac, Josipa Domitrović and Vesna Dragčević
Sustainability 2021, 13(10), 5407; https://doi.org/10.3390/su13105407 - 12 May 2021
Cited by 10 | Viewed by 2675
Abstract
Challenges that emerge in roundabout design are mostly related to space constrictions and provision of appropriate deflection around the central island. This can result in speed profiles on roundabouts that might reduce their potential as a noise abatement measure. Because of this, the [...] Read more.
Challenges that emerge in roundabout design are mostly related to space constrictions and provision of appropriate deflection around the central island. This can result in speed profiles on roundabouts that might reduce their potential as a noise abatement measure. Because of this, the impact of a roundabout on noise levels and its applicability as a traffic calming device and a noise abatement measure should be investigated in the early design stage, by modeling noise levels. In this paper, the following hypothesis is tested: vehicle movement trajectories, defined during the fastest path performance check in roundabout early design phase, can be used as the road traffic noise sources when modeling noise at roundabouts using static noise model. This procedure (1) simplifies the preparation of the noise model, (2) results in a model that is closer to the real-world in terms of traffic flow conditions, (3) allows the noise calculations in the early stages of roundabout design, and (4) includes the influence of roundabout deflection on calculated noise levels. The abovementioned simplifications of the road traffic noise modeling process should encourage the optimization of roundabout geometry in terms of its noise reduction capabilities in the preliminary design phase of these intersections. Full article
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21 pages, 2466 KiB  
Article
Roundabout Entry Capacity Calculation—A Case Study Based on Roundabouts in Tokyo, Japan, and Tokyo Surroundings
by Elżbieta Macioszek
Sustainability 2020, 12(4), 1533; https://doi.org/10.3390/su12041533 - 18 Feb 2020
Cited by 37 | Viewed by 4333
Abstract
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 [...] Read more.
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. Full article
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