Abstract
In this paper, various strategies for minimizing the amount of switching done at a classification yard are examined. We investigate how the allocation of blocks (the sorting classes recognized at the yard) to classification tracks affects switching work. Given are the sorting classes, as well as the schedule and block makeup of the departing trains. Only static strategies are considered—strategies where every block has been assigned permanently to a classification track. Simple formulas are given for the minimum number of tracks needed to implement a strategy, and for the amount of switching work given a number of tracks. The total track length is also examined. The results are significantly influenced by the number of blocks recognized by the yard; given this number, the results are nearly independent of the train departure schedule, the number of departing trains, and the number of blocks of individual trains. This feature simplifies the study of larger problems (e.g., dynamic blocking strategies) and, most importantly, makes train formation and scheduling an easier job at every yard.

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