An Analysis on Time Coverage Rate of RFID Traffic Data

In the field of road traffic status identification, parameters on "time occupancy" based on data collected from magnetic loops have been widely used.However, such data cannot be obtained from traffic flow data collection methods based RFID technologies.Based on the analyses of RFID data characteristics, this paper proposes a novel concept of Time Coverage Rate (TCR) and its calculation method.TCRs are calculated with the consideration of 7 types of time aggregation levels.Curves of base stations' TCRs taking time aggregation levels as an independent variable are drawn according to the calculation results.Status of the base stations, the volume as well as the continuity of the traffic flow at the base stations'' location can be roughly estimated based on the trends of these curves.21 RFID base stations on arterials of Nanjing are chosen for a case study in which the proposed approach is used.The results show that the curves of the TCRs can be categorized into 3 types, including: ① Daily coverage rate is less than 100%.② Daily coverage rate is equal to 100% and time aggregation is between 1 h and 5 min, TCRs are near to 100%;③ Daily coverage rate is equal to 100% and time aggregation is between 1 h and 5 min, TCRs decrease.Each type represents a certain working condition of base stations and different characteristics of traffic flow.It can be seen that, time coverage rate has practical significance for performance evaluation of RFID base stations and analyses of traffic flow statuses.