Dynamic estimators of origin-destination matrices using traffic counts

This paper proposes different ‘dynamic’ estimators using time-varying traffic counts to obtain (discrete) time-varying OD flows or average OD flows. All the estimators can combine counts with other available information, e.g., out-dated matrices and surveys, on a general network and can be formulated as optimization problems. In the case of time-varying OD flows, two types of estimators are proposed. Simultaneous estimators produce joint estimates of the whole set of OD matrices, one for each time slice, whereas sequential estimators produce a sequence of OD estimates for successive time slices. A particular type of simultaneous and sequential estimator (namely Generalized Least Squares) was tested on the Italian Brescia-Padua motorway for which ‘true’ OD flows over a whole day were available. Results were generally satisfactory, showing that also in the ‘no a priori information’ case significant estimates could be obtained.