Show transcribed image text 432 Chapter 10 Distribution and Network Models a.M. in ACTION OPTIMIZING FREIGHT CAR ASSIGNMENTS AT UNION PACIFIC* Union Pacific (UP) is one of the largest railroads in North America. It owns over 100,000 freight cars, which it uses sity to develop an optimization model to assist with the to service its customers via a network of over 30,000 miles empty freight car assignment problem. In order to be of railroad track. In response to customer demand, UP useful, the model had to be simple enough to be solhed moves empty freight cars to its customer locations, where quickly and had to run within UP's existing informa- the cars are loaded. UP then transports the loaded cars to tion systems. A transportation model was developed. destinations designated by the customers. the largest railroads in North UP partnered with researchers from Purdue Univer with supply being the empty freight cars at their current At any point in time, Union Pacific may have hun- locations and demand being the current and forecasted dreds of customer requests for empty freight cars to requests at the customer locations. The objective func transport their products. Empty freight cars are typi- tion includes not just the cost of transporting the cars, bur cally scattered throughout UP's rail network at previous other factors such as early and late delivery penalties and delivery destinations. A day-to-day decision faced by UP customer priority. This allows the managers to trad operations managers is how to assign these empty freight a variety of factors with the cost of assignments to ensun cars to current freight car re The assignments need to be cost effective but also must outputs the number of e quests from its customers. stomers. that the proper level of service is achieved. The mode that the proper level of service is achi d to be cost effective but also must outputs the number of empty cars to move meet the customers' needs in terms of service time. current locationr empty cars to move st Based on A. Narisetty et al, An Optimization Model for Emply cars. The model is used on a daily basis for operations Freight Cor Assignment at Union Pacific Railrood, Interfaces 38, no. planning and is also used to study the potential impact 2 (March/April 2008): 89-102 current location to the locations of customers s also used to study the poten changes in operational policies.