A bi-level gradient approximation method for dynamic traffic demand estimation: Sensitivity analysis and adaptive approach

The paper presents an in-depth analysis of the bi-level gradient approximation approach for dynamic traffic demand estimation. Initially, a sensitivity analysis of the parameters of Simultaneous Perturbation Stochastic Approximation method (SPSA) with Asymmetric Design (AD) and Polynomial Interpolation (PI), firstly proposed by authors in 2011, is presented. Then, an adaptive method based on the second order SPSA AD-PI approach, is explored; finally, some new advances of the estimation method are proposed in order to keep under control traffic phenomena during the estimation.