Solving Real-Life Railroad Blocking Problems

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United States railroad companies transport millions of freight cars a year over their network. Railroad companies rely on their network to move shipments from city to city and state to state. Each railroad company has a service-design department which coordinates the movement of railcars, crew, and locomotives over the railroad’s network. Creating an operating plan for the system is a challenging task because train scheduling consists of designing train routes, days of operation, timings, and routing blocks to minimize cost. The operating plan is responsible for the flow of the three important railroad assets: crew, locomotives, and cars. The expense to maintain all three commodities runs in billions of dollars.

Developing a plan requires several months of preparation time by a team of experienced service designers. The railroad industry is losing a significant amount of experienced employees due to retirement. Railroad companies are in need of software tools to decrease their dependence on people. Ravindra Ahuja, Krishna Jha, and Jian Liu created algorithms to solve the railroad blocking and train scheduling problems. Reducing railroad blocking is critical for the railroad industry in order to save cost.

A shipment can travel through many train yards on its way from its starting point to its destination. An Incoming shipment is sorted and grouped for placement on outgoing trains. However, the reclassification process of the shipment delays the movement. To prevent a shipment from being reclassified at every train yard it travels through, shipments are grouped together to form a block. Blocking is a problem in the rail industry, postal and package delivery, trucking, and the airline industry.

Mathematically, the railroad blocking issue is a multicommodity-flow, network-design, and routing problem. To solve it, the developers designed an underlying blocking network and then routed different commodities on the blocking to reduce cost....
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