Search results for " roundabout"
showing 10 items of 33 documents
Conversion of existing roundabouts into turbo-roundabouts: case studies from real world, Journal of Civil Engineering and Architecture 6(8)
2012
Compared with roundabouts the main advantages of turbo-roundabouts are the reduction in the number of potential conflicting points and the lower speed of vehicles through the intersection; they both can improve road safety conditions at the junction. Moreover, the physical delimitation among lanes limits the side-by-side accident risk. 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. The present paper has three main objectives : 1) to discuss general design criteria and functional principles of turbo roundabouts; 2) to give the geometric d…
Comparing Performances of Turbo-roundabouts and Double-lane Roundabouts
2012
Starting from assumptions regarding the arrival process of circulating streams and according to models based on the gap-acceptance theory, the paper is aimed at comparing operational performances between basic turbo-roundabouts and double-lane roundabouts. The paper proposes applications of the Hagring model for entry capacity estimations at double-lane roundabouts and turbo-roundabouts, these latter, in particular, featured by movements with only one or two conflicting traffic streams. This model allows to use, in fact, a bunched exponential distribution to quantify the distribution of major vehicle headways; it also considers specific values different by each lane for behavioural paramete…
Understanding Safety-Related Issues for Pedestrians at Modern Roundabouts. Journal of Sustainable Development, 5(4):23-37
2012
This paper examines the safety-related issues for pedestrians at modern roundabouts. For this purpose findings of research studies documented in the scientific literature and best practices have been examined trying to focus on roundabout installations by a pedestrians safety perspective. Whereas one of the main reasons for which roundabouts are built is related to safety benefits, roundabout design features and implications in road casualties have been commented first to evaluate the influence of roundabouts on pedestrian safety and then to identify design elements that have such a high potential for traffic safety. At last, measures and treatments that can be taken in the roundabouts desi…
Comparative Analysis of Four New Alternative Types of Roundabouts: “Turbo”, “Flower”, “Target” and “Four-Flyover” Roundabou
2016
Analysis of literature shows that “modern roundabouts” nowadays exist in all European countries, as well as in more than 60 countries elsewhere in the world. Nowadays, a growing number of studies, presented in scientific and professional literature, point out a poor traffic safety characteristics of “standard” two-lane roundabouts and lower capacity then was expected. These problems are resolved in more ways in different countries; however the solution, whereby the number of conflict spots is diminished has proven to be the most successful. Lower number of conflict spots is one of characteristics of the alternative types of roundabouts. The alternative types of roundabouts are usually more …
Editorial: Calculation of Passenger Car Equivalents at Roundabouts
2021
Editorial on the Research Topic: Calculation of Passenger Car Equivalents at Roundabouts About this Research Topic: Calculation of Passenger Car Equivalents (PCEs) for heavy vehicles represents the starting point for the operational analysis of road facilities and other traffic management applications. PCEs are used to consider the presence of heavy vehicles in the traffic stream and are expressed as multiples of the effect of an average passenger car. Moreover, the highly curvilinear nature of the roundabout design, both in urban and rural environment, has significant effects on the paths that heavy vehicles would travel; as a consequence, the interaction between the physical and performan…
A grid of material and immaterial laboratories for supporting the sustainability of transportation: the RESET project in Sicily
2015
Transportation is a crucial sector, to be suitably approached in order of getting human activities in more environmentally sustainable paths. In fact, in developing, as well in less developing, countries people and freights mobility are responsible of important amount of pollutant emissions and are cause of significant levels of energy consumptions. In this paper, a Sicilian regional project is presented, aiming at establishing an interconnected grid of material and immaterial laboratories. These laboratories, that are devoted at inducing more virtuous behaviors in the transportation policies, are constituted by equipment and software tools, mainly located in the region’s universities, acti…
Performance Analysis of Basic Turbo-Roundabouts in Urban Context
2012
AbstractA turbo roundabout is a new type of canalized multilane intersection in which the physical separation between lanes helps to prevent side collisions when crossing the roundabout. This paper presents an estimation of capacity, delays and level of service of basic turbo roundabouts in undersaturation conditions, considering both vehicle flow and pedestrian traffic. The traffic performance model was developed by evaluating the capacity for each entry lane. Owing to the geometric features of the intersection, the total entry capacity is obtained by considering different values of the pedestrian impedance factor and degree of saturation at both the right-turn and left-turn lanes.
Calibrating a microscopic traffic simulation model for roundabouts using genetic algorithms
2018
The paper introduces a methodological approach based on genetic algorithms to calibrate microscopic traffic simulation models. The specific objective is to test an automated procedure utilizing genetic algorithms for assigning the most appropriate values to driver and vehicle parameters in AIMSUN. The genetic algorithm tool in MATLAB® and AIMSUN micro-simulation software were used. A subroutine in Python implemented the automatic interaction of AIMSUN with MATLAB®. Focus was made on two roundabouts selected as case studies. Empirical capacity functions based on summary random-effects estimates of critical headway and follow up headway derived from meta-analysis were used as reference for ca…
Flower roundabouts: estimation of capacity and level of service
2012
The research work on road junction geometry, carried out in European research centres, has recently allowed to design new road intersection types which are of undoubted interest, especially in terms of traffic functionality and safety. Among the most interesting solutions there are such schemes as spiral, turbo and flower roundabouts, which are similar to traditional roundabouts. Although these solutions provide a traffic travels counterclockwise around a central island and in which entering traffic must yield to circulating traffic, the newly designed schemes generally offer modes of traffic flow regulations which highly differ from those used in conventional roundabouts. Of considerable i…
Turbo-roundabouts vs Roundabouts Performance Level
2012
AbstractIn this paper the performance level of basic turbo-roundabouts and double-lane roundabouts are compared. Cowan's M3 headway distribution was chosen to take into account bunched vehicles moving along each circulating lane; the Hagring model was adopted to evaluate entry capacity both at turbo-roundabout and at double-lane roundabout.The comparative analysis was performed evaluating operational performances in terms of delay suffered by users entering the intersection.Results of the analyses show that efficiency of basic turbo-roundabouts highly depend on traffic situations and can be significant when major road captures most of the traffic demand.