REAL-TIME TRAFFIC QUEUE LENGTH ESTIMATION AT THE FREEWAY OFF-RAMP USING DUAL-ZONE DETECTORS

摘要

Congestion at the downstream of a freeway off-ramp often propagates the traffic queue to the mainline, and thus reduces the freeway capacity at the interchange area. Hence, an accurate queue estimation model can help the traffic engineers to select a proper control strategy to mitigate queue spillback at off-ramps. In responds to such a need, this study presents a queue estimation model using dual-zone detectors, where each detector can provide two side-by-side detection zones. The short detection zones are used to count traffic flow rates and the information from the long detection zone can indicate the presence of traffic queues. Since depending on the congestion level in the local arterial, the off-ramp queue may or may not be fully discharged during the green time, this study has developed two queue estimation models for each condition. Based on the field data from the freeway interchange in Zhubei, Taiwan, this study has conducted extensive simulation experiments, and demonstrated the effectiveness of the proposed model for estimating the off-ramp queue.