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.