Drones help run the nation's railroads. In order to run a safe railroad, tracks must be in good shape. Drones help get the job done. They do so by flying over rail yards and around bridges, allowing ground-penetrating radar and wayside sensors to identify possible track defects. Locomotives equipped with Positive Train Control (PTC) systems have on-board computer software that automatically stops a train in certain instances to reduce specific types of human-caused errors.