A GENERATION CONSTRAINED APPROACH FOR THE ESTIMATION OF O/D TRIP MATRICES FROM TRAFFIC COUNTS

The analysis of the transportation systems know that one of the most important problems in the situation and planning of these systems is the evaluation of the origin/destination (OD) trip matrix, or in other words of the number of trips made by users in a pre fixed area and in a reference time interval by using one or more transportation modes. The accuracy of the OD estimate is a crucial aim in most practical applications because significant variations with respect to the true, unknown, trip matrix could result in incorrect forecasting of the traffic flow values on the transportation links and then in incorrect evaluation of the effects of possible modifications of the system. The methods proposed in this paper for the evaluation of the OD trip matrix can be grouped in three classes: direct estimation, model estimation and estimation from traffic counts. Among, these, the estimation from traffic counts has received a great attention in the past few years because of the cheapness of the information sources. In fact, while the first two methods require a great effort in terms of time and economic resources, because the estimate of the OD matrix is obtained by using directly or indirectly the data collected by interviews to the users, the latter method requires only the use of a set of traffic flow values, counted on some suitably chosen links of the transportation network, in order to correct and improve an initial, old estimate of the OD matrix. It is for this reason that different models and different applications have been proposed in the literature to resolve the problem of estimating the OD trip matrix by using link traffic counts, named in the following OD Count Based Estimation (ODCBE problem.