This bill amends the Intermodal Surface Transportation Efficiency Act of 1991 to designate U.S. Route 15 in Pennsylvania from its intersection with Interstate Route 180 to the New York border as part of a high priority corridor on the National Highway System. Pennsylvania shall erect signs identifying such corridor as Interstate Route 99. The Department of Transportation is authorized to make grants to Pennsylvania for projects to: erect signs identifying the segment designated by this bill as part of the Interstate System (IS), and make improvements as necessary for such segment to conform with applicable IS standards. The bill permits vehicles that could operate legally on such segment before its designation as part of the IS to continue to operate on such segment without regard to IS vehicle weight limitations.