Patent ID: 7716010

Claim:
A system for determining whether a railroad vehicle has shifted by more than a threshold distance on a pair of rails, said system comprising: said rail vehicle configured to travel along the pair of rails; a transducer positioned on an outer surface location of said rail vehicle, said transducer being aligned above an inner edge portion of said respective rail to direct a signal toward said inner edge portion located a first distance from said transducer, said inner edge portion being positioned a threshold distance outward from an inner edge of said respective rail, said transducer configured to receive said signal having reflected from one of said inner edge portion along said first distance to said transducer and a surface of the respective rail beyond said inner edge portion along a second distance to said transducer, said second distance being greater than said first distance; and a controller coupled to said transducer to receive transmission and reception data of said signal to determine whether said rail vehicle has shifted by more than said threshold distance along said respective rail, based on said signal having reflected along from the surface of the respective rail along the second distance.