Seunghyeon Lee

Real-Time Estimation of Lane-to-Lane Turning Flows at Isolated Signalized Junctions

In this paper, we develop rule- and model-based approaches for the real-time estimation of lane-to-lane turning flows. Our aim is to determine the turning proportions of vehicles based on detector information at isolated signalized junctions and thereby establish effective control strategies for adaptive traffic control systems. The key concept involves identifying the entrance lane of a vehicle detected in an exit lane at the signalized junction. Lane-to-lane turning flows are estimated by tracing the corresponding entrance lanes of the vehicle based on the detector and signal information from the set of potential entrance lanes at the junction. In the rule-based approach, the entrance lane of a vehicle detected in an exit lane is identified according to a set of specified rules. The model-based approach, which is based on utility maximization, is used to identify the most probable turns in a set of potential upstream entrance lanes. Both computer simulations and real-world traffic data show that the model-based approach outperforms the rule-based approach, particularly when turning on red is allowed, and is capable of accurate estimation under a wide range of traffic conditions in real time. However, the rule-based approach is simpler and does not require calibration, which are positive assets when no prior data are available for calibration.

Group-based approach to derivatives of delay models based on incremental queue accumulations for isolated signalized junctions

ABSTRACT We devise an approximation method for the derivatives of group-based variables in individual signal groups during each cycle of a traffic signal, based on the estimated control delay formulas and queue formation patterns. The key challenges include establishing the most appropriate formulations to estimate the derivatives of the control delay toward group-based variables for individual lanes on each cycle, according to the queuing formation pattern, and identifying the vehicular arrivals and departures occurring in the extended or the setback time duration. The derivatives of the control delay computed by the proposed methods for the variables are compared with numerical differentiations collected by simulation. The results of the two methods show good concurrence, with a few outliers for both the start and the duration of the effective green time. The proposed methods lay the foundation stone of more efficient non-linear mathematical programs to optimize group-based signal plans in real time.