Interstate 78 (I-78) is an east–west Interstate Highway in the Northeastern United States that runs 144 miles (232 km) from I-81 northeast of Harrisburg, Pennsylvania through Allentown to western and North Jersey, terminating at the Holland Tunnel entrance to Lower Manhattan in New York City. Major metropolitan areas along I-78 include the Lehigh Valley in Pennsylvania, the Gateway Region in New Jersey, and the New York metropolitan area.

Interstate 81 (I-81) is a north–south Interstate Highway in the eastern part of the United States. Its southern terminus is at I-40 in Dandridge, Tennessee; its northern terminus is on Wellesley Island, New York at the Canadian border, where the Thousand Islands Bridge connects it to Highway 137 and ultimately to Highway 401, the main Ontario freeway connecting Detroit via Toronto to Montreal. The major metropolitan areas along the route of I-81 include the Tri-Cities of Tennessee; Roanoke in Virginia; Harrisburg and the Wyoming Valley in Pennsylvania; and Syracuse in New York.