Abstract

Recently, many of the foreign traffic-safety analyses point out the low level of traffic safety in multi-lane roundabouts. This problem is resolved in several ways in different countries however, the solution, whereby the number of conflict points is diminished (e.g. turbo roundabout) has proven to be the most successful. However, the turbo roundabout also has its deficiencies: it has conflict crossing points and larger reconstruction of the existing two-lane roundabout is needed when the turbo roundabout is to be implemented instead of the existing one. In the paper a new type of roundabout has been introduced the roundabout with “depressed” lanes for right turning (“the flower-roundabout”). Financially speaking, the main advantage of the new type of roundabout is that it can be implemented within the dimensions of the already existing “normal” two-lane roundabout. From the traffic-safety point of view, the main advantage of the new type of roundabout is that it has no crossing conflict points. V zadnjem času mnoge tuje prometno-varnostne analize kažejo na nizko raven prometne varnosti večpasovnih krožnih križišč. Ta problem v različnih državah rešujejo na različne načine, kot najuspešnejši pa se je pokazal način z zmanjševanjem števila konfliktnih točk (npr. turbo krožno križišče). Vendar ima tudi turbo krožno križišče svoje pomankljivosti: ima konfliktne točke križanja ter v primeru, da želimo izvesti turbo krožno križišče namesto obstoječega dvopasovnega križišča, je potrebna večja rekonstrukcija križišča. V prispevku je predstavljen novi tip krožnega križišča - krožno križišče s "pritisnjenimi" pasovi za desno zavijanje. Glavna prednost takšnega tipa krožnega križišča je, da ga je možno izvesti znotraj meja obstoječega dvopasovnega krožišča. S stališča prometne varnosti ta tip krožnega križišča nima konfliktnih točk križanja.

Abstract

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. Problem nizke ravni prometne varnosti v obstoječih večpasovnih krožnih križiščih se v različnih državah rešuje na različne načine, običajno z uvedbo alternativnih tipov krožnih križišč, v katerih je število konfliktnih točk praviloma manjše. Za alternativne tipe krožnih križišč je tipično, da se od “normalnih” oz. “standardnih” krožnih križišč razlikujejo v enem ali več projektno–tehničnih elementov, specifični pa so lahko tudi pogoji njihove izvedbe. Danes je že znanih veliko različnih tipov krožnih križišč (“mini”, “dvojni mini”, “dumb–bell”, “s povezanima ločilnima otokoma” (“dog-bone”), “s spiralnim potekom krožnega vozišča” (“turbo”), “s pritisnjenimi pasovi za desne zavijalce” (“flower”), …) in njihov razvoj bo zagotovo potekal tudi v prihodnosti. Prispevek prikazuje novi tip krožnega križišča, dvonivojski enopasovni krožni križišči s pasovi za desne zavijalce, krajše “target roundabout”. V prispevku so predstavljene njegove projektno–tehnične, prometno–varnostne in kapacitetne lastnosti, primerjaje z običajnim dvopasovnim krožnim križiščem.

Abstract

The problem of minor vehicles crossing or merging into the major stream at unsignalized priority-controlled intersections is well-known. Numerous solutions involve various assumptions concerning the major headway distributions, number of major lanes, critical gap distributions, etc. Such cases can be divided into two main groups: intersections with two streams (one major and one minor stream) and intersections with more than two streams (more than one major stream and one minor stream). At roundabouts, also at single-lane roundabouts, there are similar problems like the ones at other unsignalized priority-controlled intersections. A vehicle at the roundabout approach can only cross the pedestrian crossing when a sufficient time-gap between two pedestrians (or cyclists) is provided. A vehicle at the roundabout entries can only merge into the major stream when a sufficient gap between the two vehicles in the major stream is provided. Because of that, single-lane round-abouts can also be treated as unsignalized intersections with two major lanes: the first one in its circulatory roadway and the second one on the pedestrian crossing. Problematika križanja ali vključevanja stranskega prometnega toka v nivojskih križiščih, kjer je prometni režim urejen z glavno in stransko prometno smerjo, je znan. Številni pristopi vsebujejo različne predpostavke, ki zadevajo porazdelitev glavnega prometnega toka, število prometnih pasov na glavni prometni smeri, kritično časovno praznino ... Take sisteme lahko razdelimo v dve glavni skupini: križišča z dvema tokoma (enim glavnim in enim stranskim) in križišča z več kot dvema tokoma (več kot dva glavna prometna toka in en stranski prometni tok). V krožnih križiščih, tudi v enopasovnih, obstajajo enaki problemi, kot pri drugih nivojskih križiščih, urejenih s prometnim režimom glavne in stranske prometne smeri. Vozilo na uvozu v krožno križišče se lahko priključi v glavni prometni tok le v primeru, ko je časovni presledek med dvema pešcema (ali kolesarjema) zadosti velika. Vsled tega lahko tudi enopasovna krožna križišča obravnavamo kot nesemaforizirana križišča z dvema glavnima prometnima tokoma: prvim v krožnem vozišču in drugem na prehodu za pešce.

Abstract

The paper demonstrates the influence of the multi-channel pedestrian flow on the actual capacity of a one-lane roundabout, using micro-simulation and discrete functions. The proposed model is based on the theory of the expected time gap between the units of pedestrian traffic flow, which have the priority when crossing the arm of the roundabout. The proposed model represents an upgrade of the previous research in the field of modelling traffic flows in the one-lane roundabout.Apart from the multi-channel pedestrian flow the disturbances caused by the circular traffic flow of motorised vehicles at the roundabout are also considered. In this way the model can better illustrate the real conditions in traffic. A simulation analysis has been performed on the roundabout arm at Koroška Street in Maribor. The results of the analysis have indicated a relatively high reserve of the actual throughput capacity for the main motorized traffic flow in the analysed roundabout arm. The presented model represents a practicable and adaptable tool for planning the roundabout capacity in practice and for the sensitivity analysis of individual variables on the throughput capacity of the roundabout. Prispevek prikazuje vpliv večkanalnega toka pešcev na dejansko propustno sposobnost eno-pasovnega krožnega križišča z uporabo mikro-simulacij in diskretnih funkcij. Predlagani model temelji na teoriji pričakovane časovne praznine med enotami prometnega toka pešcev, ki imajo pri prečkanju kraka krožnega križišča prednost pred motornimi vozili. Predlagani model predstavlja nadgradnjo predhodnih raziskav na področju modeliranja prometnih tokov v enopasovem krožnem križišču. Poleg večkanalnega toka pešcev so hkrati upoštevane tudi motnje zaradi krožečega toka motornih vozil v krožišč. S tem je doseženo, da model se bolje ponazarja realno dogajanje v prometu. Simulacijska analiza je bila izvedena na krožnem križišču, ki se nahaja na Koroški ulici v Mariboru. Rezultati analize so pokazali sorazmerno visoko propustno sposobnost glavnega prometnega toka motornih vozil v analiziranem kraku krožišča. Predstavljeni model predstavlja uporabno in prilagodljivo orodje za načrtovanje kapacitete krožišč v praksi in analiza vpliva posameznih spremenljivk na propustno sposobnost krožišča.

Abstract

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 mind the 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.

Abstract

Single-lane roundabouts may face the problems of getting crowded and empty in their circulatory roadway due to a strong stream of pedestrians and/or cyclists. Vehicles at the roundabout entries or exits have to provide the right of way over pedestrians and/or cyclists. Therefore, it comes to disturbances and traffic jams. If there are jams at the entry carriageway, vehicles are unable to get into roundabouts. If there are jams at the exit carriageway, vehicles are not able to leave the roundabout. When the length of vehicle platoon at the exits so long that it reaches the preceding entry, the roundabouts suffer from getting fully overcrowded. The paper presents the methodology of calculating the reduction of the roundabout capacity due to the pedestrian or cyclist stream. The method of calculating the reduction of the roundabout capacity with the disturbed streams may be used for roundabouts in urban environments, where the strength of the cyclist or pedestrian streams is not negligible. V krožnih križiščih z enim voznim pasom v krožnem toku lahko, zaradi močnega toka pešcev in/ali kolesarjev, nastopajo problemi polnjenja in praznjenja krožnega križišča. Vozila na vhodih/izhodih v krožno križišče morajo pešcem/kolesarjem odstopiti prednost. Vsled tega prihaja do oviranosti tokov in zastojev. V primeru, da do zastojev prihaja na vhodu, vozila ne morejo uvažati v krožno križišče. V primeru, da do zastojev prihaja na izhodu, vozila ne morejo zapuščati krožnega križišča. V primeru, ko je dolžina vozil v koloni tako dolga, da doseže predhodni vhod, prihaja do problemov s polnjenjem krožnega križišča. V prispevku je prikazana metodologija izračuna zmanjšanja kapacitete krožnega križišča zaradi tokov kolesarjev in pešcev. Metodologija izračuna zmanjšanja kapacitete krožnega križišča s pomočjo oviranih tokov je uporabna pri krožnih križiščih v urbanih sredinah, kjer so jakosti prometnih tokov kolesarjev in pešcev nezanemarljive.

Abstract

The critical and follow-up headways are the two gap-acceptance parameters which explain the traffic interaction of a minor street vehicle when enters the roundabout, merging into or crossing one or more circulating (major) streams. Several studies and researches provide measurements of critical and follow-up headways from real data at roundabouts. The objective of our research is to synthesize the data from the series of selected studies to interpret variation across the studies. In order to match the research goal, a systematic literature review on estimations of critical and follow-up headways at roundabouts was undertaken. Since several studies and researches developed worldwide were examined, we were able to note that the effect size varied from study to study. Thus the meta-analysis of effect sizes was performed as part of the literature review through the random-effects model. After discussing the assumptions of this model, the dispersion in effects across studies was assessed and the summary effect for each of the parameters under examination was computed. Calculations were made both for single-lane roundabouts and double-lane roundabouts, as well as for turbo roundabouts. Compared to the results of individual studies, the single (quantitative) meta-analytic estimate provides an accurate and reliable synthesis on the specific issue here addressed, and gives, with greater power of the individual reviewed studies, a comprehensive measure for the parameters of interest. Document type: Article