Interstate 78 is one of the shorter Interstate highways, but it certainly serves an important purpose, linking Harrisburg, Pennsylvania, to New York City. Harrisburg may not seem like an important generator of trips to New York City, but Harrisburg is where Interstate 81, Interstate 83, and the Pennsylvania Turnpike (I-76) all funnel traffic onto Interstate 78 so that said traffic can reach New York City and New England. At Harrisburg, Interstate 81 continues its northeastward journey that it's been taking through Appalachia, serving travelers from inland and south-central portions of the United States. It isn't until 20 miles beyond Harrisburg that Interstate 81 reaches a fork where Interstate 78; so, Interstate 78 doesn't begin in Harrisburg, per se. At this point of beginning northeast of Harrisburg, Interstate 81 straightens into a northward highway, as Interstate 78 continues northeasterly to Allentown and Easton. Interstate 78 crosses the Delaware River into New Jersey at Easton, and the highway goes on to do a lot of legwork when it comes to serving North Jersey's traffic. It snakes through Newark, and then enters the Holland Tunnel at Jersey City. The Holland Tunnel deposits traffic onto various streets in Manhattan, New York City, in a tight, slow turbine configuration, as Interstate 78 ends. Interstate 78 is very, very close to, if not duplexed with, US Route 22 for its entire length.
My photo of Interstate 97 signage comes from an interchange with Pennsylvania Highway 183. The venue for this photo is near the small town of Strausstown, Pennsylvania. The aperture looks north at a sign pointing out the eastbound onramp entrance to northbound travelers on the state highway. Note the inclusion of US Route 22, which is concurrent with Interstate 78 at this point (and at many other points). This photo was taken in April 2024, during my trip to Pennsylvania, the Delmarva, and the Carolinas.