Implementing Bottleneck Management Techniques and Establishing Quality of Sort Relationships to Improve Terminal Processing Capacity

The importance of classification terminals to railroad network performance is well established. As the key control points, each terminal’s performance affects many aspects of network operations from freight car utilization to service reliability. The acceptance of scheduled railroading by all Class I railroad’s in North America has heightened the interaction between terminal performance and network operations. Terminal performance is strongly affected by terminal capacity which is defined as the upper limit on the throughput of a production process. Due to constraints on capital, railroads need to harness as much capacity as possible from existing infrastructure. It is estimated that reducing terminal dwell time can result in a 1530% terminal capacity improvement without a major capital investment. Because classification terminals can be considered production systems, insight into the dynamics of a terminal system can be gained by adopting a manufacturing systems management approach. This enables use of production control tools that have led to significant capacity and performance improvement in the manufacturing environment. This work focused on improving terminal performance by adapting the Hopp & Spearman concept of “Factory Physics,” Goldratt’s Theory of Constraints (TOC) and tools from Lean Manufacturing. The most important manufacturing process analog to improving terminal capacity is the bottleneck. In a production system the bottleneck is the process that limits its throughput. As such, the processing rate of the bottleneck sets the rate for the entire system. Improving the performance of the bottleneck is the best way to improve the performance of the entire terminal system. Value Stream Mapping and TOC were used to identify and understand the relationship between the bottleneck and the rest of the terminal system on two major North American railroads, CN and Canadian Pacific. The pull-down process has been identified as the bottleneck in a majority of classification terminals, including those of CN and Canadian Pacific. Both railroads are engaged in efforts to improve terminal performance. Techniques that have proven successful in improving bottleneck performance at terminals on both railroads are discussed in the context of TOC and Lean Manufacturing. The interaction between the hump and the pull-down process is discussed in the context of the factors that increase the workload of the pull-down crews. How well the cars are sorted in the classification yard directly impacts the performance of the pull-down process. Improving the Quality of Sort can translate into an increase in terminal processing capacity and is reflected in lower average dwell times. A metric for measuring the Quality of Sort in the bowl has been developed and its relationship to bowl volume established. Methods for implementing this metric at the production control level in a terminal are also discussed. What’s new? Application of the manufacturing methodologies of Factory Physics, Theory of Constraints and Lean Manufacturing to railroad terminal operations and development of a metric to measure the quality of the sorting process. The relationship between that metric and bowl volume has been established and related to improving terminal performance.

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