Railyard Modeling: Part I. Prediction of Put-Through Time

An analytic model of railyards has been developed and is reported in two separate studies (Parts I and II). This paper (Part I) is a macroview of yards describing the major operations performed within a yard and how different yards may be classified for modeling purposes. The yard operations are analyzed as queuing phenomena and modeled using known queuing relations. These queuing models are then used to calculate the probability distribution of put-through times, and their moments, for each major type of traffic. These, distributions are compared with observed histograms. Part II will describe how the process rates in the queuing models are related to the physical configuration of the yard, the yard resources, the marshaling rules, and the traffic intensities.