California Partners for Advanced Transportation Technology

In this paper, we conduct an empirical comparison of travel time estimation methods based on single-loop detector data. The methods of concern are the regression method based on an intuitive stochastic model as proposed by Petty et al. in [7], and the conventional method of using an identity relating speed, flow and occupancy with the assumption of a common vehicle length. The analysis is tailored to fit in the limitations imposed by available field data sets. We also introduce several variations of the regression method and give examples which suggest directions for future work to further improve the regression method. The comparison is composed of three interrelated parts, each with a different focus:local comparison (concerning a single link of freeway), comparison of estimated section travel times over a prolonged stretch of freeway with multiple links and a visualized approach which enables investigation of performance patterns in time and space of the estimation methods.