Short Line Railroad Relief Act This bill authorizes the Department of Transportation to provide emergency grants or enter into contracts and other agreements for capital projects for short line railroads. A project must protect, repair, reconstruct, or replace short line railroad equipment and facilities in danger of suffering catastrophic damage, or that have suffered catastrophic damage, as a result of an emergency. An emergency includes a natural disaster affecting a wide area or a catastrophic failure from any external cause that results in the declaration of an emergency or a major disaster.