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. To prevent such queue spillback, this study proposes a real-time control strategy to provide a priority signal control to the off-ramp traffic when potential queue spillback has been detected. To contend with different congestion patterns at the freeway and local arterial, this study provides two types of priority strategy: unconditional and conditional controls, which can quickly discharge the queuing vehicles on the off-ramp. 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 strategies on preventing off-ramp queue spillbacks. Also, the experimental results reveal that the overall network performance can be significantly improved with the proposed strategy even though some roadway segments of the local arterial network may experience negative impacts.
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