Detector delay as a useful detector timing feature is often recommended to minimizing the disruptions on major movements by one or more minor movements. However, this benefit of detector delay is not always certain, because the applicability of detector delay is subject to a combination of gap demand, gap availability, critical gap acceptance, follow-up headways and other factors. Improper use of detector delay could be costly to the traffic on minor streets. With very limited literature, the complex relationship between detector delays and different critical factors has been fully understood. This paper presents an analytical model for estimating the probability of clearing the right-turn-on-red (RTOR) queues within the period of detector delay. This probability is the important first step to the understanding of how this detector feature affects the intersection operational efficiency. The gap-finding process of multiple RTOR vehicles is divided into several realistic cases and analyzed in great details. Insights of the process described in each case have been applied to the derivation of the probability model. Validation of the model is conducted using more than 4000 simulation runs. And a close fit is found between the computed probability and the simulated data, with errors no larger than 5.7% of the targeted values. The method to derive the probability model provides a stepping stone to derive the delay distributions for RTOR traffic.
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