Precision Scheduled Railroading and the Need for Improved Estimates of Yard Capacity and Performance Considering Traffic Complexity

Abstract

Multiple North American freight railroads have adopted concepts of Precision Scheduled Railroading (PSR) that attempt to reduce costs by maximizing train length and minimizing railcar transit time. To achieve these objectives, PSR emphasizes pre-blocking traffic and operating general-purpose trains. These changes have altered the nature of operations at many classification yards, leading to yard closures and conversions to different yard types. Difficulty in implementing PSR-inspired operating practices at yards suggests the industry requires improved estimates of classification yard performance and capacity. While volume-based approaches may be adequate when yard operations are consistent with historical experience, it is hypothesized that approaches considering overall traffic complexity will offer improved predictions when changes are also made to the number of blocks and trains assembled in the yard. An original simulation model of a classification yard pull-down process is used to investigate this hypothesis. The simulation results suggest that a combination of factors describing yard traffic complexity can be a better predictor of yard performance than volume alone. The results are also transformed into a capacity constraint that describes the interaction between the maximum allowable daily number of railcars, blocks, and trains processed by a classification yard. Better understanding of these relationships can aid practitioners and researchers in improving network blocking models and developing train plans that properly use available yard capacity under PSR and other operating plans, reducing the likelihood of future network disturbances and congestion events.