A Practical Method for Estimating Traffic Flow Characteristic Parameters of Tolled Expressway Using Toll Data

The primary objective of this paper is to develop a practical method for obtaining traffic flow characteristic parameters by the mining of toll data, and validate the method through an application of the method to analyses of the flow-speed relationship and the representativeness of Electronic Toll Collection (ETC) data with the toll data collected from Jinbin expressway in Tianjin. With the proposed method, traffic flow characteristic parameters of each link on the toll way could be easily captured considering four types of relationships between the vehicle position and the link without needing traffic flow data from traffic sensors. Further, flow-speed relationships of Jinbin expressway are studied and a linear flow-speed relationship is derived for each link with no significant differences between weekdays and weekends. Finally, as the index to describe the representativeness of ETC data, absolute values of the relative error of speeds between ETC data and the full toll data (ARE) are calculated, and the relationship of flow-ARE is analyzed. It is found that this relationship follows the exponential distribution, and the conclusion could be obtained that within the 10% allowable error, ETC data could be used to estimate the link speed of the entire traffic when the traffic flow rate is greater than 500veh/h.