North Dakota's grain producers rely on an efficient rail system to move their products to export and domestic markets. A recent shift to larger grain hopper cars may threaten the viability of the state's light-density branch line network. This study simulates the impacts of handling larger rail cars on many types of rail lines, model the decision process used by railroads in deciding whether to upgrade such lines or abandon them, estimates the costs of upgrading rail lines that are unlikely to be upgraded, and estimates generalized highway impacts that could result from the abandonment of non-upgraded lines