An improved approach for the sensitivity analysis of computationally expensive microscopic traffic models: a case study of the Zurich network in VISSIM

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.