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The article discusses feasible treatments for improving the performance of undivided four-lane urban roads, which suffer from poor capacity, pedestrian service, and safety, suggesting 15 potential treatments including restriping, and redirecting movements as alternatives to road diets.

The article discusses the evolution of roundabout roads in the northeastern U.S. Topics include the strong resistance of people against the construction of modern roundabout in the northeastern region despite being life-savers, failures of roundabouts in Massachusetts, and New York State Department of Transportation's (NYSDOT's) Roundabouts First property to create roundabout corridors in 2006.

Pedestrian crossing behaviour is more difficult at any rotary intersection because of less response time of pedestrian as well as vehicle. It is the most concerned problem in developing urban areas to provide proper safety and instructions to the pedestrians for the same. The aim of the paper is to provide overview of pervious papers published on pedestrian behaviour aiming at factors affecting pedestrian behaviour like crossing speeds, gender, total number of pedestrians, rules, waiting time and directions. Overall aim of the paper is to provide better safety to the pedestrians, to reduce accidents and reducing waiting time at any intersection. [ABSTRACT FROM AUTHOR]

Historically, there are several large roundabouts in Vilnius with traffic organisation and safety problems. Vilnius City Administration initiated changes on these large roundabouts in 2016, by introducing new traffic organisation schemes and using relatively simple measures such as the line markings, safety measures and road signs. The aim of the research is to analyse the number of traffic accidents on the roundabouts before and after such traffic reorganisation. The article is based on accident maps in roundabouts created by the authors. Based on the comparison of accident maps, the safety trends were analysed and summarised. [ABSTRACT FROM AUTHOR]

Historically, there are several large roundabouts in Vilnius with traffic organisation and safety problems. Vilnius City Administration initiated changes on these large roundabouts in 2016, by introducing new traffic organisation schemes and using relatively simple measures such as the line markings, safety measures and road signs. The aim of the research is to analyse the number of traffic accidents on the roundabouts before and after such traffic reorganisation. The article is based on accident maps in roundabouts created by the authors. Based on the comparison of accident maps, the safety trends were analysed and summarised. [ABSTRACT FROM AUTHOR]

In this work, we present the different steps in the modeling and implementation of a first-order macroscopic road traffic simulation tool, using Lighthill–Whitham–Richards approach with a Godunov scheme (cell transmission model) and bounded acceleration. The origin–destination traffic movement is based on the definition of partial streams according to their chosen paths or 'routes' from an origin to its destination. The resolution of the traffic conflicts at the nodes level is achieved using a modified dynamic node model. The dynamic node model proposed in this work introduces a new supply function which follows from the extension of the Highway Capacity Manual (2010) model for use in dynamic and instantaneous regime. The method is then applied to reconstruct the traffic at a roundabout in the city of Sousse, Tunisia, known to be over-jammed at rush hour. The results are satisfactory and can be generalized to other intersection types with different priority levels. [ABSTRACT FROM AUTHOR]

The article informs that Minnesota Department of Transportation (MnDOT), cities, counties, and the consultant community have made great strides in utilizing a broader range of intersection types to solve transportation problems in Minnesota with mini-roundabouts.

Recently, multirotor Unmanned Aerial Vehicles(UAVs) or drones have become increasingly popular for a vast variety of civil applications. Efficient traffic data collection and extraction of various flow parameters are some of the futuristic applications of this technology. However, such applications still need to be streamlined and thoroughly explored for varying traffic and infrastructural conditions. In this paper, the focus is on the authentication of the application of small multirotor UAVs for traffic data collection and subsequent analysis of traffic streams at urban roundabouts. This paper presents an analytical methodology to evaluate the performance of roundabouts by extracting various parameters and performance indicators. The performance evaluation methodology is based on: (i) determining traffic volume via OD matrices for each leg, and (ii) analyzing drivers’ behavior via gap-acceptance analysis. The overall analytical process is principally based on the authors’ previously proposed automated UAV video-processing framework for the extraction of vehicle trajectories. The extracted trajectories are further employed to extract useful traffic information. The experimental data to analyse roundabout traffic flow conditions was obtained in the city of Sint-Truiden (Belgium). The results reflect the value of flexibility and bird-eye view provided by UAV videos; thereby depicting the overall applicability of the UAV-based traffic analysis system. With the significant increase in the usage of UAVs expected in the coming years, such studies could become a useful resource for practitioners as well as future researchers. The future research will mainly focus on further extensions of the UAV-based traffic applications. [ABSTRACT FROM AUTHOR]

The article reports a study by the American Association of State Highway and Transportation Officials (AASHTO) that highlights the safety benefits of roundabouts in reducing severe crashes compared to conventional stop-controlled and signalized intersections.

This paper presents a regression model which is developed to estimate entry capacity of an approach on a roundabout for Indian traffic conditions. The entry capacity of an approach on a roundabout is expected to depend on the circulating traffic flow in front of that approach and the safe opportunity for vehicles entering that flow. The relationship between entry capacity and circulating traffic flow is found to be negative exponential i.e. the entry capacity decreases exponentially with an increase in the circulating traffic flow. The analysis also indicated that the widths of circulating roadways and central island diameters have a significant influence on the entry capacity. The circulating traffic flow versus entry capacity charts were made with the purpose of comparing the results of the proposed model with the existing models available in the literature, namely Jordanian, Malaysian, and Indian. The comparison indicated that the proposed entry capacity model gave the highest entry capacity, whereas the Malaysian model gave the lowest entry capacity. The results of the proposed model have shown very good relationship with the field entry flow data, as compared to other models. Hence, this model is suggested to estimate entry capacity on roundabouts under similar varied traffic flow conditions in developing countries. [ABSTRACT FROM AUTHOR]

Turbo-roundabouts are new type of roundabouts that recently become more popular for their significant advantages. Due to their specific geometry of spiral leading circulatory lanes and raised lane dividers provide a high level of traffic safety while a relatively large capacity maintain. To compare with conventional double-lane roundabouts, turbo-roundabouts ensure above all a reduced number of conflict points moreover without waving and lower driving speed through the intersection. Challenge of this paper is to transfer existing single-lane roundabout into configuration models of basic and egg turbo-roundabouts and compare their capacity characteristics. Case study is placed in Zilina, the city on the north of Slovakia, where the single lane roundabout has a great congestion problem not just during peak hours. Configurations of the roundabout are evaluated and compared from their performance parameters using microsimulations and theoretical models. For calibration procedure of microsimulation, complex data obtained from survey of existing roundabout were used and derived as input variables for two new configurations. This example is to demonstrate the capacity increase of turbo-roundabouts comparing with single-lane roundabout and the comparison of microsimulation model and theoretical models to determine capacity of turbo-roundabouts. [ABSTRACT FROM AUTHOR]

The article deals with an operation issues and traffic evaluation at selected turbo-roundabouts realized in Czech Republic. Also describes redevelopment possibility of existing roundabouts with classic layout to the roundabouts with spiral arrangement of the traffic lanes on the circulatory roadway. Described are advantages and disadvantages of the spiral arrangement in compare with normal roundabouts. The article evaluates Czech methodology of turbo - roundabout design, which was published in 2015 and compares its findings with foreign methodologies, especially Dutch and Slovakian standards. Presented are basic divisions of turbo - roundabouts and how the single types of layout are different from the point of view of number of traffic lanes and estimated capacity. There is shown the list of realized turbo - roundabouts on which is made a comparison of identity of the selected parameters of geometric elements defined in the Czech methodology with the foreign standards. Evaluation criteria of realized constructions are basic design elements of turbo-roundabouts, traffic lane (roadway) width and layout and design arrangement with aiming on problematic design features. The article also briefly deals with the evaluation of effectiveness from the point of view of capacity and traffic accidents, when are compared traffic accidents data at selected locations in Czech Republic where redevelopment of conventional types of intersections to turbo-roundabouts were made. [ABSTRACT FROM AUTHOR]

As the motorisation augments in urban areas, different solutions are required, considering the traffic network. In order to adjust the urban arrangement with the need for mobility, complex process of planning and designing is required. City development contains adequate incertitude which causes difficulty during the process of planning and designing. According to this, the process of planning and designing the city infrastructure network are mutually connected and inevitable. Traffic planning is a base of successful functioning in urban areas. With adequate analysis about city development and traffic, the planning process can begin, and be followed by the designing process and building the traffic network. Analysis of capacity and level of service are necessary, in order to obtain the delay of the analysed facilities. These analyses can be empirical and analytical. The empirical model is based on regression analysis, and the analytical model uses the gap – acceptance theory. Empirical models provide better results, but can be used in cases where few roundabouts are congested, to calibrate the model. Othewise, gap – acceptance methods are used to analyse uncongested roundabouts. [ABSTRACT FROM AUTHOR]

It is crucial to measure the performance of existing roundabouts in terms of its ability to handle the present traffic scenario. The capacity of an entry flow is found to vary immensely with the changing geometrics of the roundabout. A meticulous study was conducted to gather data from roundabouts with varying geometry and traffic characteristics. A model was developed using empirical analysis based on five such geometric parameters, which proved to be significant for estimating the capacity. The parameters used in this equation had a multiplicative relation with the conflicting flow. Every geometric has been tested individually for its influence on capacity, keeping the flow conditions constant. The developed model satisfied the practicality when validated with the site data. A comparative study with some existing empirical models indicated that the capacities of roundabouts are underestimated/overestimated for Indian scenario. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes and analyses a layout and regulation, which provides 100 % bus priority and no delays for buses at small and medium sized roundabouts. The Continuous Median Lane Roundabout (CMLR) is designed specifically for bus rapid transit (BRT) or buses with high level of service (BHLS), where buses run in median exclusive lanes. In previous solutions, access to the roundabout circulating lanes from the general purpose approach lanes has been controlled by traffic signals. In the CMLR, give way signs within the roundabout control the two conflict points between buses in the median lanes and other vehicles in the circulating lanes. Microsimulations show that there is a large and unused potential for transit priority at roundabouts. Significant reductions in delays and emissions may be achieved. [ABSTRACT FROM AUTHOR]

Roundabouts have long been regarded as an effective traffic control method. While this method is quite popular in some foreign countries like Australia, there are not as many existing roundabout sites in the U.S. According to foreign experiences and limited experience in the U.S., roundabouts can be good replacement alternatives where signalized intersections no longer function well. This research examined and monetized the potential benefits of converting signalized intersections to roundabouts under three different circumstances. To be specific, the potential benefits included crash reduction, delay time reduction, fuel efficiency improvement and air pollutant reduction. Then a benefit-cost analysis (BCA) was conducted. The monetization of environmental benefits was used to improve the BCA methodology that has been used by others. Three different intersections, that are currently signalized, were studied to determine the BCA. After a systematic evaluation, it was found that a five-way intersection with moderate traffic volume had the best benefit-cost ratio among all three intersections studied. [ABSTRACT FROM AUTHOR]

Roundabouts have long been regarded as an effective traffic control method. While this method is quite popular in some foreign countries like Australia, there are not as many existing roundabout sites in the U.S. According to foreign experiences and limited experience in the U.S., roundabouts can be good replacement alternatives where signalized intersections no longer function well. This research examined and monetized the potential benefits of converting signalized intersections to roundabouts under three different circumstances. To be specific, the potential benefits included crash reduction, delay time reduction, fuel efficiency improvement and air pollutant reduction. Then a benefit-cost analysis (BCA) was conducted. The monetization of environmental benefits was used to improve the BCA methodology that has been used by others. Three different intersections, that are currently signalized, were studied to determine the BCA. After a systematic evaluation, it was found that a five-way intersection with moderate traffic volume had the best benefit-cost ratio among all three intersections studied. [ABSTRACT FROM AUTHOR]

In the last years, as regards the functional design of at-grade intersections, near to classic layouts (signal-controlled junctions, roundabouts, etc.) a new solution has born: the “turbo-roundabout”. It is a canalized multilane oval intersection with a non-traversable or partially traversable center island and with a spiral circulatory carriageway. This kind of roundabout is also characterized by a predictable lane use: some direction flows are physically separated by curbs. Several roundabouts with spiraling circular carriageways were built in northern Europe (in particular in Netherlands) and they have further allowed to extend the notable advantages of this functional solution against multilane roundabouts, such as: 1) no lane changing on the circulatory carriageway; 2) no need to yield to traffic flow on more than two lanes; 3) low driving speed along the through movement because of raised lane dividers and, consequently, a high reduction of accident risk. In this paper a careful literature review on turbo-roundabouts is proposed. Furthermore, the Authors examine the potentialities offered by the transformation of an existing semi-two lanes roundabout into a “virtual” configuration of a turbo-roundabout. In particular, they also evaluate and compare the performance parameters in the two configurations by using a microsimulation software. The case study roundabout is placed in the city of Cosenza (Southern Italy) and it is characterized by great problems of congestion during peak hours. Experimental measures of traffic flows (O/D matrixes), critical gaps, queue lengths and approaching and circulating speeds represent input data for calibration procedures. Afterwards, derived calibration parameters are used as input variables for the new configuration of the intersection as a turbo roundabout. The Authors highlight that the conversion of the existing roundabout into a virtual turbo roundabout determine an increase of capacity together with a minimization of the queue lengths. [ABSTRACT FROM AUTHOR]

The expansion of roads and the development of new road infrastructures have increased in recent years, linked to the population growing in large cities. In the last two decades, roundabouts have largely replaced traditional intersections in many countries. They have the advantage of allowing drivers continuous flow when traffic is clear, without the usual delay caused by traffic lights. Although roundabouts with and without traffic-signal control have been widely used and considered in the literature, driverless control on roundabouts has not been studied in depth yet. The behavior of autonomous vehicles in roundabouts can be divided into three stages: entrance, inside, and exit. The first and last may be handled as an extension of intersections. However, autonomous driving on the roundabout requires special attention. In this paper, the design and implementation of a fuzzy logic system for the steering control of autonomous vehicles inside the roundabout is proposed. Cascade architecture for lateral control and parametric trajectory generation are used. Fuzzy control has proved to be easy to define using expert knowledge. Experiments with a real prototype have been carried out, taking into account different speed profiles and lane change maneuvers inside the roundabout, with very satisfactory results. [ABSTRACT FROM AUTHOR]

Copyright of Baltic Journal of Road & Bridge Engineering (Baltic Journal of Road & Bridge Engineering) is the property of Baltic Journal of Road & Bridge Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article offers information on a study on modern roundabouts and its operation and safety in relation to design consistency. Topics include the U.S. Department of Transportation Federal Highway Administration's "Roundabouts: an Informational Guide," publication, the differences between roundabouts and traffic circles or rotaries, and the findings which reveal lower crash rates for roundabouts and the high occurrence of Property Damage Only (PDO) in both rotaries and roundabouts.

Copyright of Baltic Journal of Road & Bridge Engineering (Baltic Journal of Road & Bridge Engineering) is the property of Baltic Journal of Road & Bridge Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article details a study on the effects of cycle length (CL) on the efficiency of diverging diamond interchanges (DDI) using the microscopic simulation software VISSIM. Topics covered include a quantitative methodology for creating a traffic signal operation (TSO) plan for a DD interchange, the relationship between CL and total average delay in other TS control modes like pretimed TS control, and coordinated actuated control, and the effect of the volume/capacity ratio on TSO implementation.

The article suggests ways for correct implementation of traffic calming based on the document "National Guidelines for Traffic Calming" compiled by the Department of Transport of South Australia. It discusses the impact of traffic calming measures on a road network if not correctly implemented and outlines steps to be taken before the implementation of traffic calming measures. Alternatives to traffic calming include traffic circles, traffic funnels and lifted intersections.

Alternative types of roundabouts are usually more recent and have been implemented only in certain countries. Typically, they differ from "standard" roundabouts in one or more design elements, whilst the purposes of their implementations are also specific. The main reasons for their implementations are particular the disadvantages of "standard" one- or two-lane roundabouts in particular circumstances or changes of "actual circumstances" which in the past has led to roundabout implementations. Today, several different types of roundabouts are well-known ("mini", "double mini", "dumb -- bell", "with transition central island", "with joint splitter islands", "traffic signal controlled", "assembled roundabouts" ...), and it is possible to stipulate that they will be further developed in the future. This paper illustrates two relative new alternative types of roundabouts - "turbo" and "flower" roundabouts and their comparison from design, traffic safety and capacity point of view. [ABSTRACT FROM AUTHOR]

Abstract: Concerns over exposure to airborne particulate matter (PM) are on the rise. Currently monitoring of PM is done on the basis of interpolating a mass of PM by volume (μg/m3) but has the drawback of not taking the chemical nature of PM into account. Here we propose a method of collecting PM at its emission source and employing automated analysis with scanning electron microscopy associated with EDS-analysis together with light scattering to discern the chemical composition, size distribution, and time and space resolved structure of PM emissions in a heavily trafficated roundabout in Sweden. Multivariate methods (PCA, ANOVA) indicate that the technogenic marker Fe follows roadside dust in spreading from the road, and depending on time and location of collection, a statistically significant difference can be seen, adding a useful tool to the repertoiré of detailed PM monitoring and risk assessment of local emission sources. [Copyright &y& Elsevier]

In the literature, many analytical techniques allow the study of the performance (capacity, queues, delays, etc) of roundabouts which are divided into two groups: analytical models and microscopic simulation models. Each method, when formulated, has to consider some aspects of roundabout circulation in comparison to others (geometric elements, vehicular flow and user behaviour). In particular, microscopic simulation models offer several advantages, compared to analytical ones (such as realistic modelling of vehicle arrivals and departures or the ability to study the spatial extent of queues), but they must be carefully calibrated. In this paper the authors introduce the results of a large survey conducted on an ample range of roundabout scenarios through the application of VISSIM simulation software. Each scenario describes a fixed roundabout phenomenon using geometric elements (inscribed circle radius, circular roadway, central and splitter islands etc.) and characteristics of the traffic flow (density, distribution, crossing and approach speeds, etc.) as variables. The results allow authors to evaluate the effects of these parameters on roundabout stop-line delays through a significance analysis. [ABSTRACT FROM AUTHOR]

Copyright of Baltic Journal of Road & Bridge Engineering (Baltic Journal of Road & Bridge Engineering) is the property of Baltic Journal of Road & Bridge Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Baltic Journal of Road & Bridge Engineering (Baltic Journal of Road & Bridge Engineering) is the property of Baltic Journal of Road & Bridge Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: In this paper, a comprehensive model is constructed aiming at solving traffic circle problem which greatly bothers the modern society. Firstly, the quantification approach to assess the clog degree is put forward according to the description of electrical power in circuit principles. Then making use of the economic concept of marginal cost and relationship between supply and demand, judgment can be made on the changing rule of marginal social benefit when every unit of money is spent on the issue to improve traffic circle conditions. The intersection point when marginal social benefit turns from positive to negative is the best point for government to invest on the road conditions. Combined with conflict degree, we determine using different methods under various circumstances: laying stop or yield sign, placing traffic lights, or limiting the highest speed. In addition, consulting the mechanism of primary response circuit, we establish the method to set time for traffic lights. At last, an instance analysis is set for Xiamen Lianban traffic circle and the result shows that our research can reasonably deal with the practical problem. [Copyright &y& Elsevier]

The article presents the roundabouts that offer context sensitive solutions (CSS) for practitioners looking for ways to accommodate motorized traffic while preserving what is special about the area through which it passes. Roundabouts are said to improve roadway network capacity since they usually operate more efficiently than conventional signalized intersections. It suggests the likely reduction in crashes when intersections are converted to roundabouts.

The presentation concludes a work that has determined an urban landscaping element to be carried out - the Caşin Round-About in Bucharest. The grounding of the landscaping work, its strategy, concept, proposal and implementation are followed as these depict the raw material of the study. The intervention particularities were the setup speed and the public impact of the work. This involved special horticultural approaches to respond design development need for flexibility, and work site image. The integrated outcome of the landscaping work was discussed by their horticultural, urban, economic, environmental, social, cultural, sensorial and political parameters. The field experience and its results are analysed in terms of horticultural and sustainability issues, leading to conclusions of technical, administrative and legal impact, meant to decrease the unpredictability involved in the planning and set-up stages. [ABSTRACT FROM AUTHOR]

The article focuses on the potential application of mini-roundabouts in the U.S. It discusses the proliferation of the mini-roundabouts in Great Britain. Compared with traffic signals, it notes that mini-roundabouts can operate with much reduced delay, especially during off-peak period. The similarity of mini-roundabouts with traffic circles is also noted. An overview of the design, safety, general operation, as well as traffic configurations of mini-roundabouts, is provided.

Reports on the creation of a high capacity modern roundabout interchange in the Town of Vail, Colorado. Description of a modern roundabout; Design of the Vail interchange; Use of the British application RODEL; Benefits offered by the project.

This article discusses how the critical time gap, or minimum time to cross an unsignalized intersection, for a pedestrian priority route should be based on pedestrian rather than automobile travel times to encourage walking and ensure safety. This pedestrian-based time gap impacts other intersection safety measures, such as intersection sight distance (ISD) and the gap size, or allowable crossing window for pedestrians. The time gap shouldprovide sufficient time for a pedestrian to cross without having to wait an exceptionally long time to cross safely between cars. [ABSTRACT FROM AUTHOR]

The article offers information on several news related to traffic engineering including the Traffic Engineering Handbook Webinar Series; Right Turn on Red Informational Report survey; Route Guidance Data; and Wrong Way Driving.