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

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

New Type of Roundabout: Dual One-Lane Roundabouts on Two Levels with Right-Hand Turning Bypasses – ’’Target Roundabout’’

The problems of low level traffic safety on multi-lane roundabouts have been resolved in various ways in different countries, usually by using alternative types of roundabouts that reduce the number of conflict points. Alternative types of roundabouts typically differ from "normal" or "standard" roundabouts in one or more design elements, as their implementation purposes could also be specific. Today, several different types of roundabouts are already in use ("mini", "double mini", "dumb-bell", those "with joint splitter islands" ("dog-bone"), those "with a spiralling circular carriageway" ("turbo"), those "with depressed lanes for right-hand turners" ("flower") etc.). This paper introduces a new type of roundabout, dual one-lane roundabouts on two levels with right-hand turning bypasses, namely the "target roundabout". This paper describes and analyses their design, traffic safety, and capacity characteristics, compared with the standard two–lane roundabouts

Cycling traffic at turbo roundabouts: some considerations related to cyclist mobility and safety

Abstract The growing need for sustainable mobility has led the transport policy-makers as well as population to use more of soft mobility solutions such as pedestrian and cycling traffic. Several European countries are implementing policies for total mobility with less motorization in order to reduce the negative environmental effects generated by industries and transport. In the same time new unconventional types of intersections are developed in order to ensure safer conditions not only for motorized traffic but also for pedestrians and cyclist. One of those is turbo roundabout, at-grade two-lane roundabout, introduced also in urban areas where heterogeneous traffic users are expected and on which traffic safety should be considered carefully. This article aims to analyze the safety of cyclists in different traffic conditions at turbo roundabout with and without separated traffic lanes for cyclists. Through the evaluation of level of service and surrogate safety parameters, the advantages and critical aspects linked to turbo roundabout are highlighted. The research will be conducted on theoretical turbo roundabout with substantial variation in traffic flow. Comparison of the results will allow a better understanding of functionality (level of service, traffic safety) of turbo roundabout in the presence of pedestrians and cyclists of different age. The aim of this article is to present possible solutions to enable safer introduction of cycling traffic at turbo-roundabouts and help defining conditions (number of vehicles, number of cyclist, and number of pedestrians) in which safety of cyclist is questionable and there is need for different solution

Comparative Analyse of the Two New Alternative Types of Roundabouts – Turbo and Flower Roundabout

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

Slovenian roundabouts: we did it our way

After 20 years since the first wave of roundabouts in Slovenia, there are currently more than 500 roundabouts (mini, single lane, Multi lane and Turbo) installed all over the country. Many more are expected in line with the new Slovenian Roundabout Design Regulations which has provided an opportunity for a fresh look at roundabouts in the Republic of Slovenia. This article outlines the Slovenian experiences with respect to roundabout utilization in urban areas

Prometna varnost starejših voznikov v prometu v različnih tipih nivojskih križišč

In industrialized countries people over 50 years of age represent a rapidly growing part of population. Their lifestyle is also becoming more active, which means that the percentage of older drivers in the population of all drivers is also increasing. Many different studies have shown that elderly drivers are more frequently involved in specific types of accidents, especially at intersections. In the past 15 years there was a trend of increasing popularity of roundabouts in Slovenia. Their introduction was generally supported by the arguments of increased traffic-flow capacity and traffic safety as well. The studies on which these arguments are based were performed with an “ideal” type of driver in mindthe one that fully understands new rules and reacts correctly in all situations that may occur at such intersections, where there are no light signals to guide them. An elderly person does not necessarily conform to that ideal and if the percentage of elderly drivers became significant, the premises of the above mentioned studies may not be correct anymore which in turn implies that their results could also be questioned. The present study concentrated on the evaluation of traffic safety of elderly drivers, at various types of intersection, from their own perspective. Various statistical analyses of obtained data were performed. The most important finding was that we may claim, with high degree of probability, that the average person of the age of over 60 feels more unsafe at double-lane roundabouts than they would feel had the same intersection been equipped with traffic lights. Elderly traffic participants will always cause more accidents or participate in them due to hazardous factors. Challenge, arising from many different studies and researches, is in studying what measures and solutions can reduce the risk for elderly participants.Veliko število študij kaže, da se starost prebivalstva povečuje. To velja tudi za Evropsko unijo, hkrati pa tudi za Slovenijo. Statistične analize kažejo, da se v državah Evropske unije življenjska doba prebivalstva letno povišuje. V Sloveniji je 21,6% populacije starejše od 60 let. Dejstvo je, da je večina teh ljudi udeležencev v prometu, predvsem v cestnem prometu. Članek prikazuje rezultate študije, katere osnovni namen je bil analiza dejanske varnosti starejših udeležencev v cestnem prometu v Sloveniji. Raziskava je imela dva osnovna cilja. Prvi cilj je bil ugotoviti, ali se starejši udeleženci v obstoječih prometnih razmerah počutijo varne. Drugi cilj je bil usmerjen v ugotavljanje varnosti starejših oseb v različnih tipih nivojskih križišč, kjer so udeleženi v cestnem prometnem dogajanju kot pešci, kolesarji in vozniki. Rezultati anketiranja so pokazali, da se največje število starejših oseb, ne glede na to, ali so to pešci, kolesarji ali vozniki motornega vozila, najbolj varno počuti v semaforiziranih križiščih in najmanj varno v dvopasovnih krožnih križiščih. Starejši udeleženci v prometu bodo zaradi dejavnikov tveganja vedno med tistimi skupinami udeležencev cestnega prometa, ki pogosteje povzročajo nesreče oziroma so v njih udeleženi. Izziv, ki izhaja iz opravljenih študij in raziskav, je povezan predvsem s proučevanjem ukrepov in rešitev, s katerimi lahko vplivamo na zmanjšanje tveganja starejših udeležencev v prometu