Comparative Analysis of Four New Alternative Types of Roundabouts: "Turbo", "Flower", "Target" and "Four-Flyover" Roundabout

Tollazzi, Tomaž; Mauro, Raffaele; Guerrieri, Marco; Renčelj, Marko

doi:10.3311/ppci.7468

Cited by 37 publications

(27 citation statements)

References 11 publications

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“…One vehicle transfers from the circulatory carriageway (within the curve) to the road section before the roundabout (usually a straight line), which is a safer solution from the traffic safety point of view. In effect, driving through a flower roundabout is not unlike like doing so at "standard" two-lane roundabouts, but this roundabout type "forgives errors", that is, if a driver mistakenly stays in the left lane at the entrance, it still allows them to turn right at the next exit [2]. Finally, perhaps the best characteristic of the flower roundabout is that it can be implemented within the existing "standard" two-lane roundabout, as evidenced in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…In effect, driving through a flower roundabout is not unlike like doing so at "standard" two-lane roundabouts, but this roundabout type "forgives errors", that is, if a driver mistakenly stays in the left lane at the entrance, it still allows them to turn A turbo roundabout is an innovative and potentially more sustainable arrangement of a two-lane roundabout, where certain directional flows are separated or run alongside physically separated lanes (Figure 1b). These roundabouts aim to overcome such problems as two-lane roundabouts being too small and the inner circulatory lanes not being comfortable for younger and senior drivers because they feel insecure when changing lanes on a circulatory carriageway [2]. In a turbo roundabout, the traffic flows in separate paths even before actual entry into the roundabout, then occupies separate lanes throughout the roundabout, and also separate paths when exiting the roundabout.…”

Section: Introductionmentioning

confidence: 99%

“…Building on previous research where the issue of alternative roundabouts was investigated [1,2], microsimulation is used to simulate traffic operations at roundabouts with standard and newer layouts at various levels of traffic volume. Performance measures include emissions and level of service, as well as measures of safety, including conflicts and speeds, both estimated from trajectories generated in the microsimulation.…”

Section: Introductionmentioning

confidence: 99%

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Using Microsimulation to Evaluate Safety and Operational Implications of Newer Roundabout Layouts for European Road Networks

et al. 2017

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"Standard" roundabouts, for example those designed in some European countries, can often be characterized by low levels of safety or capacity and a high degree of sustainability. Given the proliferation of newer layouts, it is of interest to explore whether design practices could be improved by capitalizing on the experience gained internationally. Operational aspects of some of these designs have been explored previously, but there is a need to compare both the operational and safety performance of new designs to that of standard roundabouts. The objective of this paper is to evaluate the safety and operational implications of various potential alternatives to the standard roundabouts that proliferate in Europe and elsewhere. Microsimulation is used to simulate traffic operations at roundabout layout alternatives at the same levels of volume to capacity (V/C) ratio and also with the same traffic flow. Operational performance measures include the common level of service parameters, while measures of safety are based initially on time to collision (TTC) values. Threshold values of TTC were then applied in defining conflicts that are used for crash-based safety evaluation by applying crash-conflict models estimated in published research. Interesting insights were revealed, suggesting that the newer layouts should be considered where warranted by cost-benefit considerations.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Using Microsimulation to Evaluate Safety and Operational Implications of Newer Roundabout Layouts for European Road Networks

et al. 2017

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“…In conclusion, roundabouts differ from other circular intersections because of the following features: traffic control (yield control on all entries); priority to circulating vehicles (they have the right-of-way); pedestrian accesses (only across the arms of the roundabouts); no parking allowed; counter-clockwise circulation on the ring [26]. On the contrary, stop control or no control at all can occur on traffic circles, circulating traffic can be required to yield to entering traffic, pedestrians can cross through to access to the central island, parking can be allowed.…”

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confidence: 98%

Design of the First Italian Roundabout with Jointed Plain Concrete Pavement

et al. 2018

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This work presents the results of the overall design of the first Italian roundabout with jointed plain concrete pavement. The examined case study complies with current international standards and practices for geometry of roundabouts and road pavements. The construction of a concrete pavement in an urban roundabout will better manage and slow down fast vehicular flows, and increase traffic fluidity in an important junction, trafficked by heavy vehicles, where maintenance works should be reduced to avoid queues. The design of the roundabout involved several competences for: defining the geometry of the four-arm junction, designing the thickness of the jointed plain concrete pavement both on the circular crown and the arms, studying the mix design of a high resistance concrete. As regard to the pavement, the result of the study was an un-dowelled concrete pavement composed of square slabs laid on a cement concrete subbase and a granular layer. The shape of the slabs has been designed to optimize the structural performance of their material, which is a high strength concrete mix derived from an extensive laboratory test work. In general, the results summarized approaches typical of different design conditions: urban ones for traffic flow and safety needs; high-traffic ones for the chosen pavement type; airport ones for the absence of dowel and tie bars at the joints. Indeed, the article has highlighted that the design process of a concrete roundabout requires multiple analyses to consider various features and correctly re-design an existing urban junction. Its geometrical design, the structural design of the concrete pavement and the theoretical and experimental design of the concrete mix were the main phases of this process and they needed different competences to conduct comprehensive and appropriate analyses.

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“…A crash type is a logical category into which one or more similar crash natures are classified. Crash type is determined by the initial event in any sequence of events in a road traffic crash [9,20].…”

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confidence: 99%

Investigating the Possibilities of Specific Crash Type at Roundabouts

Somasundaraswaran¹,

Richardson²

2019

JTTE

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A comprehensive analysis of road crashes is extremely supportive in identifying existing deficiencies and in proposing new the design strategies. There are several research studies carried out for improving safety at roundabouts with the aim to altering conflict types, reducing the drivers' speeds and crash severity, and highlighting a considerable differences in the safety performance of individual or group of roundabouts. The main purpose in this study was to explain the correlation between the types of crashes to the geometry of the roundabouts based on data collected from ten top poorly performing roundabouts in Toowoomba, Australia. Preliminary analysis revealed the following as top three types as prominent at these identified roundabouts such as angle crashes (74%), hit-object crashes (13%), and Rear-end crashes (9%). Excess proportion of specific crash method has been used as methodological tool to estimate the potential possibilities for a specific crash type exceeding threshold at each roundabout. Results show that eight out of ten roundabouts were regarded for a particular type of crash but only two roundabouts were viewed for two types of crashes such as angle and hit-object.

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Comparative Analysis of Four New Alternative Types of Roundabouts: "Turbo", "Flower", "Target" and "Four-Flyover" Roundabout

Cited by 37 publications

References 11 publications

Using Microsimulation to Evaluate Safety and Operational Implications of Newer Roundabout Layouts for European Road Networks

Using Microsimulation to Evaluate Safety and Operational Implications of Newer Roundabout Layouts for European Road Networks

Design of the First Italian Roundabout with Jointed Plain Concrete Pavement

Investigating the Possibilities of Specific Crash Type at Roundabouts

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