2013 Session: 769

• An improved approach for the sensitivity analysis of computationally expensive microscopic traffic models: a case study of the Zurich network in VISSIM
  Abstract: Microscopic traffic simulators are useful tools for designing, evaluating and optimizing transportation systems. In order for a simulator to accurately describe reality, the corresponding traffic model must be properly calibrated. However, the calibration can be rather difficult when the model is computationally expensive and has many parameters. To overcome these difficulties, Sensitivity Analysis (SA) can be applied as an essential instrument for supporting model calibration. Through SA the practitioners can obtain valuable information about the relationship between model inputs and outputs, and hence focus on the proper set of most influential parameters for the calibration. In this paper we developed an SA approach based on the Elementary Effects (EE) method. It screens the most influential parameters in a complex model through computing the corresponding EE and qualitatively comparing the Sensitivity Indexes. With the improved sampling strategy, this approach is much more efficient than the original EE method.A case study of the Zurich network in VISSIM is included here to illustrate the methodology of the proposed approach. The results demonstrate its efficiency and accuracy. In addition, they show that it can be a very useful tool for the SA of computationally expensive microscopic traffic models like VISSIM, as well as other complex models in the general scientific community.
  Authors: Ge, Qiao; Menendez, Monica
  Authors: Ge, Qiao; Menendez, Monica
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 769
  Paper Number: 13-0075
• From Theory to Practice: Gaussian Process Meta-Models for Sensitivity Analysis of Traffic Simulation Models: Case Study of Aimsun Mesoscopic Model
  Abstract: This paper discusses a metamodel-based technique for model sensitivity analysis and applies it to the Aimsun mesoscopic model. Throughout the paper it is argued that the application of sensitivity analysis is crucial for the true comprehension and correct use of the traffic simulation model while also acknowledging that the main obstacle to an extensive use of the most sophisticated techniques is the high number of model runs they usually require.For this reason we have tested the possibility of performing sensitivity analysis not on a model but on its metamodel approximation. Important issues arising when estimating a metamodel have been investigated and commented on in the specific application to the Aimsun model. Among these issues is the importance of selecting a proper sampling strategy based on low discrepancy random number sequences and the importance of selecting a class of metamodels able to reproduce the inputs-ouputs relationship in a robust and reliable way. Sobol sequences and Gaussian process metamodels have been recognized as the appropriate choices.The proposed methodology has been assessed by comparing the results of the application of variance-based sensitivity analysis techniques to the simulation model and to a metamodel estimated with 512 model runs, on a variety of traffic scenarios and model outputs. Results confirm the powerfulness of the proposed methodology and also open up to a more extensive application of sensitivity analysis techniques to complex traffic simulation models.
  Authors: Ciuffo, Biagio Filippo; Casas, Jordi; Montanino, Marcello; Perarnau, Josep; Punzo, Vincenzo
  Authors: Ciuffo, Biagio Filippo; Casas, Jordi; Montanino, Marcello; Perarnau, Josep; Punzo, Vincenzo
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 769
  Paper Number: 13-1533
• Goodness of fit function in the frequency domain for robust calibration of microscopic traffic flow models
  Abstract: In the field of traffic simulation, the calibration of uncertain inputs against real data is usually taken to cover both the epistemic uncertainty regarding the un-modeled details of the phenomena and the aleatory not predicted by the models. For this reason, model parameters are usually indirectly estimated within an optimization framework which tries to maximize the fit between real and simulated measures of the traffic system. This is the case, for example, of the calibration of car-following models’ parameters against vehicle trajectory data. Only recently, it has been proven that the capability of the optimization framework to provide the parameters’ values that allow the car-following model reproducing real trajectories at its best is strictly connected to the setting of the optimization framework itself. This, in particular, entails the necessity to carefully choose an appropriate combination of optimization algorithm and measure of goodness of fit (GOF). In this study, the authors focus attention on this latter issue. Specifically, it is claimed here that the commonly used GOFs are not able to capture the dynamics of the time-series which calibration is performed against. Therefore, a spectral analysis based approach to evaluate the overall performance of the simulation model in the objective function is proposed. The new measure of goodness of fit is tested in the calibration of the Intelligent Driver Model against synthetic and real trajectory data. Results with synthetic data, in particular, confirm that such a new optimization setting is always able to find the global optimum of the problem.
  Authors: Punzo, Vincenzo; Montanino, Marcello; Ciuffo, Biagio Filippo
  Authors: Punzo, Vincenzo; Montanino, Marcello; Ciuffo, Biagio Filippo
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 769
  Paper Number: 13-3478
• Simplified Procedure for Calibrating Microscopic Traffic Simulation Models
  Abstract: Traffic simulation models have been widely used in supporting decision making process by assessing potential impacts of new operational strategies, physical investments, etc. Studies have shown that simulation models need to be well calibrated to ensure the findings from the simulation model are reliable. While the previously developed procedure by authors well demonstrated that microscopic traffic simulation models can be properly calibrated and validated using the systematic procedure, the procedure required basic knowledge in statistical analyses and the use of genetic algorithm-based optimization method. This was in part why the procedure was mostly adopted by researchers and was not widely used by practitioners. In this paper, a simplified procedure was developed and tested for more practical applications. The proposed procedure does not require the genetic algorithm (GA)-based optimization. Two case studies dealing with the calibration of an urban signalized corridor and a freeway merge section in VISSIM simulation software showed that the proposed simplified procedure outperforms the previous GA-based calibration procedure. Based on the fitness values indicating the quality of calibrated parameter set, the proposed procedure produced more promising parameter sets having better fitness value than that obtained by the GA-based procedure. In addition, while the GA-based procedure produced a single optimal solution, the proposed procedure was able to generate multiple optimal solutions outperforming the GA-based solution.
  Authors: Lee, Joyoung; Park, Byungkyu (Brian); Won, Jongsun; Yun, Ilsoo
  Authors: Lee, Joyoung; Park, Byungkyu (Brian); Won, Jongsun; Yun, Ilsoo
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 769
  Paper Number: 13-4190
• Statistical Calibration for Data-Driven Microscopic Simulation Model
  Abstract: For many decades efforts have been made to solve transportation problems. A number of research efforts have been geared toward developing accurate traffic simulation models. One of the challenges is that the model does not always adequately reflect field conditions without proper calibrations. This paper aims to highlight the importance of proper calibrations by providing a statistical calibration procedure based on the NGSIM Next Generation Simulation (NGSIM) dataset. First, a Monte Carlo approach is employed to generate candidate parameter sets for calibration. Simulations with these parameter sets are evaluated against a robust set of calibration criteria including startup and saturation flow characteristics and travel time distributions. The parameter sets that satisfy these criteria are considered as adequately calibrated. The results suggest that parameters determining distance between cars under various conditions are dominant meeting the evaluation criteria. The results suggest that this approach offers a robust and effective method of calibrating simulation models where disaggregate level vehicle data are available.
  Authors: Henclewood, Dwayne Anthony; Suh, Wonho; Rodgers, Michael Owen; Hunter, Michael P.
  Authors: Henclewood, Dwayne Anthony; Suh, Wonho; Rodgers, Michael Owen; Hunter, Michael P.
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 769
  Paper Number: 13-2978
  Practice-Ready: Yes
• An improved approach for the sensitivity analysis of computationally expensive microscopic traffic models: a case study of the Zurich network in VISSIM
  Authors: Ge, Qiao
  Authors: Ge, Qiao
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management
  Session: 769
  Paper Number: 13-0075
• From Theory to Practice: Gaussian Process Meta-Models for Sensitivity Analysis of Traffic Simulation Models: Case Study of Aimsun Mesoscopic Model
  Authors: Casas, Jordi
  Authors: Casas, Jordi
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management
  Session: 769
  Paper Number: 13-1533
• Statistical Calibration for Data-Driven Microscopic Simulation Model
  Authors: Henclewood, Dwayne
  Authors: Henclewood, Dwayne
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management
  Session: 769
  Paper Number: 13-2978
• Goodness of fit function in the frequency domain for robust calibration of microscopic traffic flow models
  Authors: Montanino, Marcello
  Authors: Montanino, Marcello
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management
  Session: 769
  Paper Number: 13-3478
• Simplified Procedure for Calibrating Microscopic Traffic Simulation Models
  Authors: Lee, Joyoung
  Authors: Lee, Joyoung
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management
  Session: 769
  Paper Number: 13-4190