Geometric design of turbo roundabouts

Džambas, Tamara; Ahac, Saša; Dragčević, Vesna

doi:10.17559/tv-20151012162141

Cited by 10 publications

(11 citation statements)

References 13 publications

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“…In the Vissim model, vehicles traveling inside the roundabout were allowed to change lanes only when approaching the objective exit, which is in accordance with actual operations. The turbo design adapted in this case is referred to as the rotor type [23] (Figure 2a). We kept the essential features of the original when we adapted it to Lujiazui (Figure 2b).…”

Section: Simulation and Data Extractionmentioning

confidence: 99%

“…The vehicle volume, composition, traveling speed and average traveling time from the videos were manually extracted. The schematic diagrams of (a) the rotor design in [23] for a four-leg roundabout and the (b)…”

Section: Simulation and Data Extractionmentioning

confidence: 99%

“…The primary four-leg forms are given in the design guidelines of the Netherlands [20], Slovenia [21] and Serbia [22], including the egg, basic, knee, spiral and rotor turbo roundabout. Among them, the egg, basic, knee and spiral roundabouts are suitable for conditions when traffic flow from a single approach is predominant, while rotor or star roundabouts are recommended for equal traffic volumes at all entries [23]. The variants can be further modified by varying the number of entry lanes.…”

Section: Introductionmentioning

confidence: 99%

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Safety and Efficiency Analysis of Turbo Roundabout with Simulations Based on the Lujiazui Roundabout in Shanghai

et al. 2020

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Traditional multilane roundabouts have many branch lanes without traffic signs and channelization, which leads to a high tendency for traffic collisions. Turbo roundabouts are a new design that has the potential to reduce lane-change conflicts using canalization to force drivers to keep in specific lanes based on their intended destination. This paper evaluates the safety and efficiency performance of turbo roundabouts for the case of a five-leg roundabout called Lujiazui in Shanghai and provides design and construction guidelines when applying the turbo design. The models for the Lujiazui roundabout and the reconstructed turbo version were built in Vissim, and a comprehensive series of experiments under different traffic volumes and central island radii was performed. Afterward, the conflict statistics extracted from the trajectory files in the Surrogate Safety Assessment Model (SSAM) were analyzed using the conflict severity index (CSI) and were then integrated to calculate the modified conflict frequency (MCF) for safety performance evaluation. A comparative efficiency analysis was also conducted as a supplement. Based on the results, the relative characteristics for safety and efficiency between the turbo and original designs of the Lujiazui roundabout were analyzed. Suggestions to apply the turbo design on a five-leg roundabout are introduced.

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Section: Simulation and Data Extractionmentioning

confidence: 99%

Section: Simulation and Data Extractionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Safety and Efficiency Analysis of Turbo Roundabout with Simulations Based on the Lujiazui Roundabout in Shanghai

et al. 2020

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“…The idea of the turbo roundabout was very rapidly (just over a few years) transposed into several countries, such as Slovenia [16], Germany [2], Denmark, Lithuania [17] and Czech Republic [18], as well as Hungary, and several other countries. For example, analysis of design approaches for turbo roundabout planning in various European regions, comparative analysis of turbo roundabout design procedures described in Slovenian technical specifications, Serbian design manual, German working document, and Croatian and Dutch guidelines was already made in the past [19].…”

Section: Functional Characteristics Of Turbo Reducedturbo Flower Anmentioning

confidence: 99%

Comparative Analysis of "Turbo", "Reduced-Turbo", "Flower" and "Semi-Turbo" Roundabout

Tollazzi

Zgrablić

Bergoč³

et al. 2020

Teh. vjesn.

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A growing number of studies, presented in scientific and professional literature, point out a poor traffic safety characteristic of "standard" two-lane roundabouts, and lower capacity than expected. These problems are resolved in different ways in different countries; however, the most successful solution has proven to be reducing the number of conflict points. Lower number of conflict points is one of the characteristics of alternative (or unconventional or no-widespread) types of roundabouts. Alternative types of roundabout differ from "standard" two-lane roundabouts in one (or more) design elements, while the purpose of their implementation is also specific. This paper illustrates two established alternative types of roundabouts (turbo and flower roundabout), and two alternative types of roundabouts in development phase (reduced-turbo and semi-turbo roundabout), offering their detailed functional description, and comparison of their capacity and traffic safety characteristics. Comparative analyses of turbo, reduced-turbo, flower and semi-turbo roundabouts was made by evaluation approach based on simulation of traffic operating at four types of alternative design layouts, including exact geometric layout of the traffic site and the precise representation of traffic flows, with turning movements, through origin-destination matrixes. The capacity comparison was conducted by a software tool VISSIM, while the traffic safety comparison was made by a software tool SSAM. In traffic safety analyses, microsimulation was used to simulate traffic operations at various levels of traffic volume. Performance measures were obtained, including measures of traffic safety, based on conflicts estimated from trajectories generated in microsimulation. According to the results, level of traffic safety (as well as capacity) of analysed alternative types of roundabouts depends on traffic flow strength, and on numbers of right-hand and left-hand turning vehicles. Consequently, for different circumstances, there are different optimal alternative types of roundabouts.

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“…This scheme was characterized by a spiraling circular carriageway with lanes separated by curbs. The main benefits of these new roundabout layouts are: a limited number of potential conflict points, a slower speed along the circulatory lane, and a low risk of side impacts [13][14][15][16][17][18]. The main negative aspects are due to the presence of through conflict points in left-turning maneuvers, higher values of the critical gaps along the road, and generally lower capacity than conventional double-lane roundabouts [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Safety Improvements by Converting a Standard Roundabout with Unbalanced Flow Distribution into an Egg Turbo Roundabout: Simulation Approach to a Case Study

Gallelli

Vaiana

2019

Sustainability

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In 2011, the United Nations Road Safety Collaboration (UNRSC) developed a Global Plan for the Decade of Action for Road Safety 2011–2020. Among the categories or “pillars” of activities, is the improvement of road safety for infrastructures. Furthermore, this plan is aligned by the UN Sustainable Development Goals that included even traffic safety. In this regard, this study estimates safety improvements achieved by converting a standard roundabout into an egg turbo roundabout. In particular, turbo roundabouts have become very popular in Northern Europe for both their safety and their capacity. Many studies have shown these advantages thanks to their features: preventive separation of entering flows, limited lane changing and low speeds due to curbs. Given the absence of existing turbo roundabouts in Italy, this research studied and compared a “virtual” roundabout with spiraling circular carriageways to an existing multi-lane roundabout in order to assess its significant reduction in terms of potential collisions. This study relied on traffic conflicts in micro-simulation by using VISSIM software and then Surrogate Safety Assessment Model (SSAM). The research is based on the traffic process observed at a standard roundabout in Cosenza (Italy) marked by a high level of congestion and safety problems. Speeds, critical gaps, queue lengths, and floating car data, obtained from video observations, have been used as input data for the calibration procedure of the first scenario (case study roundabout). Then, the turbo roundabout solution was built and simulated by using the previously derived parameters. Finally, the two roundabout scenarios were compared in terms of spatial distribution of the potential conflicts determined by SSAM. The results could help to measure the performance and safety impact of these two roundabout configurations.

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Geometric design of turbo roundabouts

Cited by 10 publications

References 13 publications

Safety and Efficiency Analysis of Turbo Roundabout with Simulations Based on the Lujiazui Roundabout in Shanghai

Safety and Efficiency Analysis of Turbo Roundabout with Simulations Based on the Lujiazui Roundabout in Shanghai

Comparative Analysis of "Turbo", "Reduced-Turbo", "Flower" and "Semi-Turbo" Roundabout

Safety Improvements by Converting a Standard Roundabout with Unbalanced Flow Distribution into an Egg Turbo Roundabout: Simulation Approach to a Case Study

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