Analysis of the influence of car-following input parameters on the modelled travelling time (original) (raw)
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Microsimulation models are widespread for the analysis of roundabouts operational performance providing realistic modelling of vehicle movements. These models are based on many independent parameters to describe traffic and driver behaviour, which need to be calibrated in order to better match field data. In practice, despite the well-recognized importance of calibration and validation processes, simulation is conducted under default values because of difficulties in field data collection and deficiency in available guidelines. These issues can be faced by using transferability methodologies that allow applying the parameters calibrated for a case study to other similar locations. Therefore, this paper investigates the suitability of the transferability procedure adopting both the application-based and estimation-based approaches, by considering two roundabouts and a microsimulation tool. A Genetic Algorithm technique was used to determine the best estimates of these model parameters. After that, the authors compared field-measured with simulated queue lengths, considering four different scenarios. The results show that the application of Wiedemann 99 parameters calibrated for the first case study to the second one allows reducing the RMSNE more than 50%, thus confirming an acceptable level of transferability of these parameters between the two case studies.
The performance of roundabouts can affect urban transport systems in terms of environmental and operational impacts, safety and efficiency. The development of roundabout traffic management and control systems can be carried out through road traffic micro-simulation models which are computer models where the movements of individual vehicles travelling around road networks are determined by using simple car following, lane changing and gap acceptance rules. Unfortunately, despite the great diffusion of these tools, appropriate methods are still needed in order to validate and calibrate these models. In general, the calibration process can be defined in this way: the process of comparing model parameters with real-world data to ensure that the model realistically represents the traffic environment. The objective is to minimize the discrepancy between model results and measurements or observations. The aim of this paper is the presentation of a first comparative approach between observed performances and performances obtained by the use of popular microsimulation software, in particular urban intersections such as roundabouts. In particular, an experimental investigation is designed and carried out in order to acquire some vehicular parameters for a roundabout placed in an urban contest of southern Italy. The calibration process is carried out by an analysis of variance of the kinematic parameters of an n-tuple of roundabout scenarios. This calibration procedure has permitted to derive some important conclusions about the choice of the most significant input parameters for the output results of each simulation scenario. Outcomes of this study are expected to benefit both practitioners and researchers.
Operating speed profiles approaching a roundabout: experiments and micro-simulation
It is well known that roundabouts performance can affect urban transport systems in terms of safety, environmental and operational impacts. Roundabout traffic management and control can be carried out by using road traffic microsimulation models. Unfortunately, for these tools appropriate methods are still needed in order to validate and calibrate these models. On the other hand, the operating speed-profile is a useful tool for the analysis of safety issues on existing roads or intersections. As far as a roundabout is present, models and tools are needed to estimate a reliable operating speed-profile on the road section along which driver speed behaviour is affected by the intersection. Consequently, the object of the paper is to analyse operating speed vs. geometry relationship and to calibrate a micro-simulation model, based on experimental investigations and simulations. In light of the above fact, driver speed behaviour (approaching and departing from roundabouts) was studied and a procedure to predict the operating speed-profile along a road section characterized by the presence of a roundabout was developed. A traffic micro-simulation model was used and its results were compared with experimental data. Micro-simulation outputs and data modelling permitted to derive some important conclusions about operating speed-profiles of each simulation scenario. Outcomes of this study are expected to benefit both practitioners and researchers.
2012
Nowadays, the functional design of a road junction is carried out by the use of the microsimulation models software, but it is important to underline that, despite the great diffusion of these instruments, there has not been the same improvement of appropriate methods in order to validate and calibrate these models. The main target to pursue is to know which and how many input parameters are most significant for the variation of output results that microscopic simulation software is able to provide. In this study, Authors present and complete a calibration procedure between observed performances of a roundabout placed in a city in province of Cosenza (ITALY) and performances obtained by the use of micro-simulation software (VISSIM). Two sets of scenarios different among them only for the traffic flow distribution were analyzed: Free Flow Condition (FFC), from which to derive the average speed profiles along a through movement; and Saturation Flow Condition (SFC), to determine the av...
Comparison between Modelled and Measured Travelling Time in Urban Roundabouts
2014
For the analysis of the existing and planned segments of the traffic system, a traffic modelling is used, and the choice of models depends on temporal and spatial limits of a model and the context of application of modelling results. Functioning of a traffic system is under the influence of variable human behaviour. Researches show that the behaviour of a driver is, among other things, territorially and culturally conditioned. Accordingly, there is no universally applicable model, so the adjustment of modelling to local characteristics of traffic system and its users is a necessary prerequisite for the use of any traffic model. The success of modelling of urban traffic networks and its segments is interrelated with successful modelling of critical network segments. According to a number of criteria, the most critical point of every traffic system is the intersection. The simulation models are very useful tool for the analysis of existing critical network segments and prediction of t...
Calibration of VISSIM roundabout model: A critical gap and follow-up headway approach
Word Count (6189 + 5 Figures×250 + 2 Tables×250) = 7939 words (Revised 11/15/2012) TRB 2013 Annual Meeting Paper revised from original submittal. ABSTRACT 1 VISSIM roundabout models have been widely applied in practice to facilitate analyzing the 2 operational performance of roundabouts. To prepare a VISSIM roundabout model for analysis, 3 an essential prerequisite is to calibrate the model by adjusting parameters until real-world 4 roundabout operations are reproduced in the simulation model. Previous calibration research has 5 used qualitative analysis to study the impact of VISSIM parameters on roundabout capacity. 6 Comprehensive calibration guidelines, parameter values based on field data, and quantitative 7 sensitivity analyses of parameters are necessary to facilitate accurate modeling of roundabouts. 8 This paper addresses these important needs. Speed trajectories of free-flow entering vehicles 9 were collected in the field using a radar sensor. Analysis identified that the approach to a 10 roundabout entrance can be divided into four speed zones reflecting different stages of drivers' 11 deceleration maneuver. Location, length, speed distribution, and deceleration rate parameters for 12 the VISSIM Reduced Speed Areas (RSA) were determined through the analysis of the radar 13 data. Comparisons between Conflict Areas (CA) and Priority Rules (PR) were also investigated, 14 and revealed that using PR can result in more consistent and repeatable gap acceptance behavior. 15 In addition, the impact of VISSIM parameters on critical gap and follow-up headway was 16 quantitatively analyzed through sensitivity analysis of minimum gap for PR, speed distribution 17 and deceleration rate for RSA, and additive and multiplicative settings for the Wiedemann 74 18 model. Numerical recommendations for calibrating VISSIM roundabout models were ultimately 19 developed, and validated via a case study. Meeting Paper revised from original submittal. Li, DeAmico, Chitturi, Bill, Noyce 42 In recent years, as many intersections in the U.S. have been converted to, or originally built as 43 roundabouts, analyzing roundabout operations and safety has drawn extensive attention from 44 practitioners and researchers. Most commercial microscopic traffic simulation software packages 45 offer the capability of building roundabout simulation models. VISSIM roundabout models have 46 been heavily discussed as one of the most widely applied microscopic simulation packages for 47 modeling roundabouts (1-12). In order for a simulation model to provide useful output, an 48 essential prerequisite is to prove that the established simulation model can accurately mimic real-49 world traffic operations. In other words, the simulation model has to be calibrated through 50 adjusting model parameters and be validated through comparison with field ground truth data 51 before the model can be used for analysis. 52
Calibrating Microsimulation Parameters for Vehicular Travel Time
International Journal of Emerging Trends in Engineering Research (IJETER), 2021
Travel time is one of the simplest yet the most important parameter for transportation facility users as well as transportation engineers. Travel time data is valuable for widerange of transportation analysis including congestion management, transportation planning and passenger’sdecision making.Traffic simulation models are now becoming necessary tools to understand the behavior of traffic and reduce vehicular travel times, but it is very important to calibrate these models first. Thisstudy attempts to determines the values of those parameters,using microsimulation,that significantly affect the travel time. These parameters arethenused for calibrating the traffic simulation model that results in realistic travel time.Study was conducted on an urban road andfield data was collected during weekdays for peak hours. The traffic network was modelled usingVISSIM®.The calibration parameters were desired speed distribution, number of lanes,average standstill distance and minimum headway. After calibrating the model, the travel times collected from field data and those by simulations for different modes of transportation were in close agreement.
h i g h l i g h t s A traffic micro-simulation calibration methodology for heterogeneous traffic is proposed. Linear regression models using sensitive parameters were developed. Genetic algorithm based optimization was adopted to obtain optimal parameter values. Different sets of optimal driving behavior parameter for different vehicle classes are suggested. The optimal parameter sets were found to vary significantly across vehicle classes. Available online xxx Keywords: Traffic operation Micro-simulation Heterogeneous traffic Vehicle-class Driver behavior VISSIM a b s t r a c t Traffic micro-simulation is a widely accepted tool in many countries for the evaluation and assessment of alternative design schemes. However, for several developing countries , replicating heterogeneous, non-lane based traffic in a micro-simulation framework is gaining increased importance and still remains a challenge due to its complexity. The present study demonstrates a methodology to calibrate a traffic micro-simulation model giving due consideration to vehicle-class specific driver behavior in an urban Indian scenario for a midblock section and an intersection approach in Kolkata. The sensitive parameters affecting the driver behavior were identified for every vehicle type using Latin Hypercube design, taking vehicle class specific travel time as a performance measure. Linear regression models were developed for each vehicle class considering the sensitive driving behavior parameters. The models highlight that the dependency of measure of effectiveness (MOE) of one vehicle type is not only limited to its own driver behavior but also on parameters of other vehicle classes. A genetic algorithm based optimization was adopted to obtain optimal parameter sets for different vehicle classes. The optimum values were found to vary significantly across all vehicle classes at a 95% confidence level. Single and multi-criteria calibration principles are also implemented to yield much more realistic results and subsequently minimizing weighted error for all vehicle classes. Please cite this article as: Maheshwary, P et al., A methodology for calibration of traffic micro-simulator for urban heterogeneous traffic operations, Journal of Traffic and Transportation Engineering (English Edition), https://doi.
Methodological Approach for Evaluation of Roundabout Performances through Microsimulation
Applied Mechanics and Materials, 2013
In the literature, there are many methodologies that allow the evaluation of roundabout performances (Capacity, Levels Of Service, etc.): analytical models (HCM, HBS etc.), statistical models (TRRL, SETRA) etc. Each technique considers some aspects of the roundabout in comparison to others (geometric elements, vehicular flow and behavioral parameters). Obtained results are often not comparable among themselves because of distinctive peculiarities of each method. Today, the best way to solve this problem is by using a refined simulation software of vehicular circulation. However, along with a more and more refined analysis of microsimulation software algorithms, it is frequently necessary for each user (researcher, engineer, planner, etc.) to know the real sensitivity of these packages with regard to the most important key parameters. In this paper the Authors introduce the results of a wide survey conducted on an ample range of virtual roundabout scenarios by the use of a modern simulation software. Each scenario describes a fixed roundabout phenomenon using the following variables: geometric elements (inscribed circle radius, circulatory roadway, central and splitter islands etc.); characteristics of the traffic flow (dynamic traffic assignment, approach speed, circulatory speed and reduced speed zones, etc.); behavioral features (priority rules, minimum gap, minimum headway, etc.). The results are presented from the evaluation of stop-line delays.