ANALIZA UTJECAJA PARAMETARA KOLONE VOZILA NA MODELIRANO VRIJEME PUTOVANJA

The calibration process is a basic condition of traffic model application in local conditions. The choice of input parameters, which are used in calibration process, influences the success of the calibration process itself; therefore, the goal is to choose parameters with a larger influence on the modelling process. This paper offers a detailed analysis of car-following input parameters and their influence on the modelled travelling time. The experimental basis was a one-lane roundabout, and the tool used for traffic simulation was the VISSIM microsimulation traffic model. The results show that the car-following input parameters should be a part of the set of input parameters, which will enter the process of calibration. The examined car-following input parameters affect the capacity of intersections and results show that it is necessary to revise the range of input values of one of the observed car-following input parameters.Postupak kalibracije je uvjet primjenjivosti prometnih modela u lokalnim uvjetima. Izbor ulaznih parametara koji će ući u postupak kalibracije utječe na uspješnost postupka kalibracije, pa je cilj odabrati parametre koji imaju veći utjecaj na rezultate modeliranja. U ovom radu detaljnije su analizirani parametri kolone vozila i njihov utjecaj na modelirano vrijeme putovanja. Eksperimetalna baza bilo je jednotračno kružno raskrižje, a kao alat prometnih simulacija služio je VISSIM mikrosimulacijski model. Rezultati pokazuju da parametri kolone vozila trebaju biti u skupu ulaznih parametara koji će ući u postupak kalibracije. Promatrani parametri kolone utječu na propusnu moć raskrižja, a rezultati pokazuju da je potrebno revidirati raspon ulaznih vrijednosti jednog od analiziranih parametara

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

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 trac safety characteristics of "standard" two-lane roundabouts and lower capacity then was expected. These problems are resolved in more ways in dierent 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 recent and implemented only in certain countries. It is typical for them that they dier from "standard" one- and two-lane roundabouts in one or more design elements, while the purpose of their implementation is also specific. This paper illustrate four relative new alternative types of roundabouts – "turbo", "flower", "target" and "four flyover" roundabouts and their comparison from designing, capacity and trac – safety point of view

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

Modern Roundabouts: A Challenge of the Future

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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

Analysis of the influence of car-following input parameters on the modelled travelling time

Postupak kalibracije je uvjet primjenjivosti prometnih modela u lokalnim uvjetima. Izbor ulaznih parametara koji će ući u postupak kalibracije utječe na uspješnost postupka kalibracije, pa je cilj odabrati parametre koji imaju veći utjecaj na rezultate modeliranja. U ovom radu detaljnije su analizirani parametri kolone vozila i njihov utjecaj na modelirano vrijeme putovanja. Eksperimetalna baza bilo je jednotračno kružno raskrižje, a kao alat prometnih simulacija služio je VISSIM mikrosimulacijski model. Rezultati pokazuju da parametri kolone vozila trebaju biti u skupu ulaznih parametara koji će ući u postupak kalibracije. Promatrani parametri kolone utječu na propusnu moć raskrižja, a rezultati pokazuju da je potrebno revidirati raspon ulaznih vrijednosti jednog od analiziranih parametara.The calibration process is a basic condition of traffic model application in local conditions. The choice of input parameters, which are used in calibration process, influences the success of the calibration process itself; therefore, the goal is to choose parameters with a larger influence on the modelling process. This paper offers a detailed analysis of car-following input parameters and their influence on the modelled travelling time. The experimental basis was a one-lane roundabout, and the tool used for traffic simulation was the VISSIM microsimulation traffic model. The results show that the car-following input parameters should be a part of the set of input parameters, which will enter the process of calibration. The examined car-following input parameters affect the capacity of intersections and results show that it is necessary to revise the range of input values of one of the observed car-following input parameters

Assessing the impact of closely-spaced intersections on traffic operations and pollutant emissions on a corridor level

Traffic lights or roundabouts along corridors are usually installed to address location-specific operational needs. An understanding of the impacts on traffic regarding to highly-congested closely-spaced intersections has not been fully addressed. Accordingly, consideration should be given to how these specific segments affect corridor performance as a whole. One mixed roundabout/traffic light/stop-controlled junctions corridor was evaluated with the microscopic traffic model (VISSIM) and emissions methodology (Vehicle Specific Power – VSP). The analysis was focused on two major intersections of the corridor, a roundabout and a traffic light spaced lower than 170 m apart under different traffic demand levels. The traffic data and corridor geometry were coded into VISSIM and compared with an alternative scenario where the traffic light was replaced by a single-lane roundabout. This research also tested a method to improve corridor performance and emissions by examining the integrated effect of the spacing between these intersections on traffic delay and vehicular emissions (carbon dioxide, monoxide carbon, nitrogen oxides, and hydrocarbons). The Fast Non-Dominated Sorting Genetic Algorithm (NSGA-II) was used to find the optimal spacing for these intersections. The analysis showed that the roundabout could achieve lower queue length (∼64%) and emissions (16–27%, depending on the pollutant) than the traffic light. The results also suggested that 200 m of spacing using the best traffic control would provide a moderate advantage in traffic operations and emissions as compared with the existing spacing

Reduction of the roundabout capacity due to a strong stream of pedestrians and/or cyclists

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

The methodology for establishing feasibility of constructing roundabouts

In slightly less than twenty years roundabouts have become very popular in Slovenia. Lately, we can add, their acceptance is almost euphoric. Presently we have one roundabout on every 68 km of national roads, while their increasing quantity can be expected. In view of the fact that lately there have also been many unacceptable independent demands for their construction, in places where they would be unsuitable, the need for calming such desire is necessary. The article deals with the methodology for establishing acceptability for construction of roundabouts in urban environments and in their real physical circumstances