The Class 1 railroads in North America have made substantial investments in mainline and intermodal terminal capacity during the past two decades to meet growing traffic demand. Investments to increase hump classification yard capacity have been less frequent, with a handful of yard projects in the late 1990s and the last major round of new hump yards constructed in the late 1970s. At this time of large investment in yards, much basic research was conducted on hump yard design and performance, while more recent studies have looked at applying lean process improvement and block optimization to hump yards. Due to the complexity of the problem, these studies tend to focus on one aspect of the terminal capacity question at a time, leaving the industry without a comprehensive understanding of the fundamental interrelationships between all aspects of hump yard performance in terms of volume, utilization and reliability. Without such an understanding, the industry cannot make fully informed decisions regarding the hump yard capacity investments that are now the subject of renewed interest due to the combination of carload market shifts, traffic growth facilitated by mainline capacity investment, and aging congested yard infrastructure. To address this need, CSX Transportation developed its Hump Yard Simulation System (HYSS). HYSS considers the operations, process and infrastructure parameters of a hump yard, and their interactions, in a single simulation to evaluate terminal performance. In the HYSS graphical environment, users can evaluate any combination of changes to terminal operating plans, yard processes and infrastructure layout. While developed to address specific business needs, as a simulation tool, HYSS has the potential to investigate the fundamental relationships governing hump yard operations in a manner not possible before. To realize this potential, CSX is partnering with the Rail Transportation and Engineering Center (RailTEC) at the University of Illinois to deploy HYSS in an academic research environment. Design of experiments techniques will be used to conduct a series of HYSS simulations to quantify the interaction between hump yard throughput, number of blocks and the delivered level of service at the terminal, and the sensitivity of this relationship to other operational and infrastructure variables. This paper will introduce HYSS as a research tool, examine how its various outputs are used to quantify terminal performance, and describe the planned research program aimed at advancing the science of hump yard design and operations.

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