Interstate 78 originates in a rural area east of Harrisburg, Pennsylvania and ends at the Holland Tunnel linking Jersey City, New Jersey with Manhattan, New York. The freeway provides a trucking corridor to North Jersey from Central Pennsylvania in lieu of the tolled Pennsylvania and New Jersey Turnpikes. Through the Allentown, Bethlehem and Easton area, the freeway acts as a bypass along South Mountain and Morgan Hill to Alpha, New Jersey.
East from the Delaware River, Interstate 78 intertwines with New Jersey Route 173 (the former alignment of U.S. 22) across Musconetcong Mountain to the Spruce Run Reservoir area and Clinton. U.S. 22 emerges along an route independent of I-78 east from Lebanon to Newark while I-78 stays north to Berkeley Heights, New Providence and Summit. The two routes converge east from Union and Irvington at the interchange complex with New Jersey Route 21, U.S. 1/9 by Newark Liberty International Airport (EWR).
Beyond the freeway along U.S. 1/9 leading north to Pulaski Skyway and I-95 (New Jersey Turnpike), Interstate 78 shifts onto the tolled New Jersey Turnpike Extension across Newark Bay to Jersey City. The limited access route ends at the one way couplet of 12th and 14th Streets between Jersey Avenue and the Holland Tunnel west portal. This stretch travels at-grade through four signalized intersections.
The Holland Tunnel carries motorists below the Hudson River to the area of Hudson Square and Soho in Manhattan, New York. Eastbound I-78 emerges at a loop encircling St. John’s Park with five ramps departing in succession to the adjacent street grid between Hudson and Varick Streets. The westbound beginning includes ramps from Canal Street, Watts Street and Varick Street two to three blocks to the north.
Interstate 78 in New Jersey is part of High Priority Corridor 63: Liberty Corridor.
Interstate 78 parallels or directly replaced U.S. 22 from near Harrisburg, Pennsylvania east to Newark, New Jersey. The New Jersey Turnpike Extension loops to the south opposite U.S. 1/9 along the Pulaski Skyway.
Origins of I-78 predate the Interstate system with a 1950 upgrade of U.S. 22 to an expressway from the Lebanon County line to Exit 13 (PA 501). The four lane roadway extended east from PA 501 at Bethel to Exit 17 (PA 419) in 1951. Work continued with construction of the Lehigh Valley Thruway from Allentown to the Delaware River commencing in 1952. The Thruway was finished in 1955, as was the portion between PA 419 and Exit 19 (PA 183 by Strausstown). When the Interstate system was established in 1958, two additional sections of U.S. 22 freeway were completed: Exits 23 to 30 (Hamburg) and from Exit 30 to the Lehigh County line.1
All of Interstate 78 west of the Lehigh Valley Thruway was completed in 1970.1 Resistance from residents of Phillipsburg, New Jersey in 1968 halted work on the connection from the Lehigh Valley Thruway to Interstate 78 east of Alpha. This led to the eventual realignment of I-78 to the south of Allentown, Bethlehem and Easton. Work on the new I-78 broke ground in 19841, with completion on November 21, 1989.2
Through New Jersey, Interstate 78 was completed in August 1986 when the controversial section through Watchung Reservation was finally opened to traffic.3 The New Jersey Turnpike Extension was constructed between 1954 and September 1956. The Holland Tunnel opened to traffic on November 13, 1927. It consists of a 8,371 foot long tube for eastbound and a 8,558 foot tube for westbound.4
The planned eastern extent of Interstate 78 through New York City included the following routes east and north to Interstate 95 in the Bronx:
- Lower Manhattan Expressway (unconstructed) – from the Holland Tunnel east to the Williamsburg Bridge
- Williamsburg Bridge (opened in 1903) – east to the Bushwick Expressway
- Bushwick Expressway (unconstructed) – east to the Nassau Expressway at Southern Parkway
- Nassau Expressway (completed eastbound in 1971, westbound unbuilt) – east to the Clearview Expressway
- Clearview Expressway (completed from NY 25 northward in 1963) – north to the Throgs Neck Bridge
- Throgs Neck Bridge – (opened in 1961) north to a split with Cross Bronx Expressway (I-78 mainline and Throgs Neck Expressway (I-78 Spur).
I-78 was deleted through New York City between Interstate 278 (Brooklyn-Queens Expressway) and the planned junction of the unconstructed Bushwick Expressway at the Nassau Expressway by the American Association of State Highway and Transportation Officials (AASHTO) on June 23, 1969. The same action redesignated I-78 along the short Nassau Expressway as Interstate 878 and I-78 along the Clearview Expressway north from Hillside Avenue as Interstate 295.