Lane-Based Queue Length Estimation in Heterogeneous Traffic Flow Consisting of Cars and Buses

Queue length is the most important traffic evaluation index used for traffic signal control at signalized intersections. Most previous studies focused on estimating the queue length in homogeneous traffic flow, but they ignored the difference of the vehicle arrival and the change of traffic flow parameters in heterogeneous traffic flow. In this paper, the authors first use the mixed platoon dispersion model (MPDM) and modify it based on the variation of queue length to estimate the arrival of cars and buses. Furthermore, the heterogeneous traffic flow parameters are analyzed using the heterogeneous traffic flow model and the queue length is estimated with the shock waves of the mixed classes. This approach fully describes the relationship between the disparate upstream traffic arrivals (due to vehicles making different turns) and the variation of the incremental queue accumulation (IQA), and makes up for the shortcomings of the uniform arrival assumption in previous research. The model was tested in a field experiment, the results of which show that the model has satisfactory accuracy and robustness. In addition, its precision is higher than that of the queue length estimation using a single-class model that uses the passenger car unit (PCU) approach to capture the heterogeneity. The limitations of the proposed model are also discussed in this paper.