Estimating Path Flows from Traffic Counts

Abstract

The theory and use of the Path Flow Estimator (PFE) as a one-stage network observer in support of urban traffic management and control is presented. Following an outline of the theory, initial results from the CLEOPATRA and COSMOS projects are reported. Underlying the PFE is a flexible capacitated stochastic user equilibrium traffic assignment method which provides unique estimates of path flows and path travel times from traffic count and prior origindestination data. To accommodate transitory overloading, time-dependent delay functions are used whereby final queues in one time slice are passed forward as initial queues for the next. The PFE is programmed in C, and can run on a variety of platforms. Efficient use of memory means that large networks can be handled in real time on a PC, although the algorithm stores and processes individual paths.