A railroad’s operating plan consists of railroad blocking and train scheduling. The blocking plan specifies how railcars between a specific origin-destination pair of locations are routed over the train network. Creating a blocking plan for a railroad is a very large-scale optimization problem, since it needs to determine the optimal routing of hundreds of thousands of origin-destination pairs of shipments. As patterns or shipment volumes on a railroad network change, the blocking plan needs to be reoptimized. BNSF Railway, the second largest freight railroad in North America, licensed our blocking optimizer and integrated it with its main planning platform.