A supplemental restraint for a primary vehicle restraint system for an auto-rack railroad car which reduces or eliminates movement of the vehicle in the auto-rack railroad car. The supplemental restraint is adapted to be positioned on a grating between the tire of the vehicle and the primary restraint. One embodiment of the supplemental restraint includes a body and an expander connected to the body. After the primary restraint is locked in place on the grating, the expander of the supplemental restraint is expanded. The expansion causes a more secure engagement between the tire and the primary restraint. This causes a high level of engagement between the tire and the primary restraint system indirectly through the supplemental restraint. The supplemental restraint also maintains a higher contact area on the tire regardless of the position of the primary restraint.