This paper presents a simple methodology to estimate queue length on an approach to a signalized intersection. This method has a minimal set of data requirements specifically flow, occupancy, cycle length, and detector setback in contrast to prevailing methods that rely on estimating vehicle trajectories using detailed data defined on a per signal cycle basis. The key element of the algorithm is the estimation of two baseline occupancies that correspond to the relative position of the queue with respect to the detector location. The results of the algorithm have been evaluated using traffic simulation and also compared to field observations. The comparison of the queue estimates suggest that the detector location would be ideal to estimate queues, if under prevailing conditions the tail of the queue is routinely longer than the detector setback. For detectors with appropriate setback, queue estimates match well in both comparisons. This algorithm was developed as part of the Midtown in Motion project and is currently operational in the field, in New York City as one of the elements of the active traffic management.
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