To amend title 35, United States Code, to clarify the applicability of certain provisions relating to railroad cars.

Amends Federal patent law denying any patent infringement for the use of an invention in any vessel, aircraft or vehicle of any country which affords similar privileges to vessels, aircraft or vehicles of the United States, entering the United States temporarily or accidentally, if the invention is used exclusively for the needs of the vessel, aircraft or vehicle and is not offered for sale or sold in or used for the manufacture of anything to be sold in or exported from the United States. Applies this denial of patent infringement for temporary presence in the United States to use of an invention in a railroad car that enters and leaves the United States on a recurring basis.