Railroad Blocking Optimizer​

Norfolk Southern


Norfolk Southern, one of the largest freight railroads in the United States, was looking for a better software solution to generate an optimal blocking plan. After licensing our blocking optimizer, the railroad integrated this solution within its own planning system, the Operating Plan Developer (OPD). This system is now an integral part of Norfolk Southern’s operating plan development process.


Business Problem

Norfolk Southern, one of the largest freight railroads in the United States, has built an extensive suite of railroad planning and scheduling systems that its service planners routinely use.  At the center of this suite is the Operating Plan Developer (OPD), which simulates the movement of railcars for a given blocking plan and train schedule. A blocking plan specifies how railcars between a specific origin-destination pair of locations are routed over the railroad network. A good blocking plan moves railcars along the shortest paths in the network and minimizes their rehandling. Norfolk Southern was seeking a software solution to generate an optimal blocking plan. It engaged with Optym to license our blocking optimizer and develop enhancements to meet its unique business practices.

Our Approach

Through several years of R&D, we had already developed an algorithm to solve the railroad blocking problem. This algorithm is based on the very large-scale neighborhood (VLSN) search technique and minimizes the weighted sum of distances traveled by shipments, their intermediate handling and transit times. Our pilot project for Norfolk Southern demonstrated that our blocking optimizer could generate implementable blocking plans, and we showed the potential benefits of these plans compared to those already in use at the company. To model its unique business practices, Norfolk Southern requested that we enhance our optimizer in several ways to incorporate new functionalities and modify the current ones. We helped integrate our blocking optimizer with Norfolk Southern’s in-house simulation system OPD.

Key Benefits

  1. Thanks to our blocking optimizer, Norfolk Southern’s service design department can now revise its blocking plan in a matter of days – a process that used to take weeks to months.
  2. Norfolk Southern frequently uses our solution to improve blocking plans as shipment volumes change.
  3. The railroad uses our system to redirect traffic in the event of any disruption, such as track flooding and train derailment.


Our blocking optimizer is now an integral component of Norfolk Southern’s service design suite. In addition to using our optimizer to periodically optimize its blocking plan, the railroad also utilizes our blocking optimizer for special studies, such as upgrading or downgrading a yard, adding a new yard location, removing an existing yard location, changing a yard’s blocking or adjusting car processing capacity.