A TWO-STEP APPROACH FOR THE CORRECTION OF THE SEED MATRIX IN THE DYNAMIC DEMAND ESTIMATION

In this work deterministic and stochastic optimization methods are tested for solving the Dynamic Demand
Estimation problem. All the adopted methods demonstrate the difficulty in reproducing the correct traffic
regime, especially if the seed matrix is not sufficiently close to the real one.
Therefore, in this paper a new and intuitive procedure to specify an opportune starting seed matrix is
proposed: it is a two-step procedure based on the concept of dividing the problem into small-size problems,
focusing on specific OD pairs in different steps. Specifically, the first step focuses on the optimization of a
subset of OD variables (the ones who generate the higher flows or the ones who generate the bottlenecks on
the network). In the second step the optimization works on all the OD pairs, using as starting matrix the
matrix derived from the first step. In this way is possible to use a more performance optimization method for
every step, improving the performance of the method and the quality of the result with respect to the classical
“one-step” approach.
The procedure has been tested on the real network of Antwerp, Belgium, demonstrating its efficacy in
combination with different optimization methods.