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Using neural networks in the process of calibrating the microsimulation models in the analysis and design of roundabouts in urban areas
Irena Ištoka Otković, 2011, doktorska disertacija

Opis: The thesis researches the application of neural networks in computer program calibration of traffic micro-simulation models. The calibration process is designed on the basis of the VISSIM micro-simulation model of local urban roundabouts. From the five analyzed methods of computer program calibration, Methods I, II and V were selected for a more detailed research. The three chosen calibration methods varied the number of outgoing traffic indicators predicted by neural networks and a number of neural networks in the computer program calibration procedure. Within the calibration program, the task of neural networks was to predict the output of VISSIM simulations for selected functional traffic parameters - traveling time between the measurement points and queue parameters (maximum queue and number of stopping at the roundabout entrance). The Databases for neural network training consisted of 1379 combinations of input parameters whereas the number of output indicators of VISSIM simulations was varied. The neural networks (176 of them) were trained and compared for the calibration process according to training and generalization criteria. The best neural network for each calibration method was chosen by using the two-phase validation of neural networks. The Method I is the calibration method based on calibration of a traffic indicator -traveling time and it enables validation related to the second observed indicator – queue parameters. Methods II and V connect the previously described calibration and validation procedures in one calibration process which calibrates input parameters according to two traffic indicators. Validation of the analyzed calibration methods was performed on three new sets of measured data - two sets at the same roundabout and one set on another location. The best results in validation of computer program calibration were achieved by the Method I which is the recommended method for computer program calibration. The modeling results of selected traffic parameters obtained by calibrated VISSIM traffic model were compared with: values obtained by measurements in the field, the existing analysis methods of operational roundabouts characteristics (Lausanne method, Kimber-Hollis, HCM) and modeling by the uncalibrated VISSIM model. The calibrated model shows good correspondence with measured values in real traffic conditions. The efficiency of the calibration process was confirmed by comparing the measured and modeled values of delays, of an independent traffic indicator that was not used in the process of calibration and validation of traffic micro-simulation models. There is also an example of using the calibrated model in the impact analysis of pedestrian flows on conflicting input and output flows of vehicles in the roundabout. Different traffic scenarios were analyzed in the real and anticipated traffic conditions.
Ključne besede: traffic models, traffic micro-simulation, calibration of the VISSIM model, computer program calibration method, neural networks in the calibration process, micro-simulation of roundabouts, traffic modeling parameters, driving time, queue parameters, delay
Objavljeno: 02.06.2011; Ogledov: 3613; Prenosov: 252
.pdf Celotno besedilo (13,21 MB)

New type of roundabout: dual one-lane roundabouts on two levels with right-hand turning bypasses - "target roundabout"
Tomaž Tollazzi, Goran Jovanović, Marko Renčelj, 2013, kratki znanstveni prispevek

Opis: 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.
Ključne besede: roundabouts, alternative types of roundabouts, turbo roundabout, target roundabout
Objavljeno: 05.06.2017; Ogledov: 278; Prenosov: 123
.pdf Celotno besedilo (1,33 MB)
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New type of roundabout: roundabout with “depressed” lanes for right turning - “flower roundabout”
Tomaž Tollazzi, Marko Renčelj, Sašo Turnšek, 2001, kratki znanstveni prispevek

Opis: 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.
Ključne besede: traffic safety, roundabouts, turbo roundabout, roundabout with "depressed" lanes for right turn
Objavljeno: 05.06.2017; Ogledov: 389; Prenosov: 138
.pdf Celotno besedilo (896,59 KB)
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Reduction of the roundabout capacity due to a strong stream of pedestrians and/or cyclists
Tomaž Tollazzi, 1999, izvirni znanstveni članek

Opis: 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.
Ključne besede: road traffic, roundabouts, roundabout capacity, traffic throughput, bicyclists, pedestrians
Objavljeno: 05.06.2017; Ogledov: 335; Prenosov: 43
.pdf Celotno besedilo (1,66 MB)
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Roundabout arm capacity determined by microsimulation and discrete functions technique
Tomaž Tollazzi, Matjaž Šraml, Tone Lerher, 2008, izvirni znanstveni članek

Opis: 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.
Ključne besede: roundabouts, traffic flow analysis, micro-simulation modelling, capacity analysis
Objavljeno: 05.06.2017; Ogledov: 486; Prenosov: 45
.pdf Celotno besedilo (4,50 MB)
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The contribution to the procedure of capacity determination at unsignalized priority-controlled intersections
Tomaž Tollazzi, 2004, pregledni znanstveni članek

Opis: 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.
Ključne besede: unsignalized intersection, roundabouts, capacity, two major streams, pedestrians, critical gap
Objavljeno: 06.06.2017; Ogledov: 235; Prenosov: 53
.pdf Celotno besedilo (2,55 MB)
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Traffic safety of older drivers in various types of road intersections
Tomaž Tollazzi, Marko Renčelj, Vlasta Rodošek, Borut Zalar, 2010, pregledni znanstveni članek

Opis: 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.
Ključne besede: traffic safety, road intersections, roundabouts, elderly people
Objavljeno: 06.06.2017; Ogledov: 429; Prenosov: 151
.pdf Celotno besedilo (811,32 KB)
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