HCM 2000 Back of Queue Model for Signalised Intersections

Abstract

A major improvement in the latest edition of the US Highway Capacity Manual is the introduction of a back of queue model for signalised intersections. The model was derived by simplification of the more general form used in the aaSIDRA (SIDRA INTERSECTION) software. The report describes the HCM 2000 queue model fully, and presents comparisons with microscopic simulation data, real-life data and aaSIDRA estimates. The theoretical background to the development of the model is discussed, and a method for determining model parameters in the case of unequal lane utilisation is given. The model uses progression factors for platooned arrivals consistent with the HCM 2000 delay model. The model can estimate the average back of queue, as well as 70th, 85th, 90th, 95th and 98th percentile queue values. A model to predict the queue clearance time is also given for use in the opposed (permitted) turn model and the actuated signal timing method. The back of queue measure is useful for identifying spillback conditions (i.e. the blockage of available queue storage distance). The queue storage ratio measure is presented for this purpose. The queue model allows for an initial queued demand at the start of the flow period.