Interstate 78

Interstate 78
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Name	Interstate 78
Route	I-78
Length mi	143.56
Established	1957
Direction	A=West
Terminus A	near Union Township, Lebanon County, Pennsylvania
Direction B	East
Terminus B	at Holland Tunnel approach, New York City
States	Pennsylvania; New Jersey; New York (state)

Interstate 78 is a major east–west United States Numbered Highway System corridor linking the Lehigh Valley, New Jersey suburbs, and the New York metropolitan area. The route provides a primary freight and commuter artery between Harrisburg, Pennsylvania regional connections and the Holland Tunnel approach in Manhattan, traversing industrial centers, river crossings, and Appalachian foothills. It forms part of national freight networks used by carriers operating between the Mid-Atlantic states, the Port of New York and New Jersey, and interstate interchanges with routes toward Boston, Philadelphia, and the Midwest.

Route description

I-78 begins near Lebanon County, Pennsylvania connecting with U.S. Route 22 (US 22) and proceeds eastward through the Lehigh Valley region, passing near Allentown, Pennsylvania, Bethlehem, Pennsylvania, and Easton, Pennsylvania. The highway traverses the Blue Mountain (Pennsylvania) gap and intersects major corridors including Interstate 81, Interstate 476, and U.S. Route 209 (US 209), facilitating access to Wilkes-Barre, Pennsylvania and the Pocono Mountains. Entering New Jersey near Phillipsburg, New Jersey, the route crosses the Delaware River via the Lehigh Valley Railroad Bridge/Delaware Water Gap corridor and continues through Hunterdon County, New Jersey, Somerset County, New Jersey, and Union County, New Jersey, serving suburbs of Trenton, New Jersey and Newark, New Jersey. Major interchanges with Interstate 287, U.S. Route 1/9 (US 1/9), and Interstate 95/New Jersey Turnpike link to ports, terminals, and commuter rail hubs such as Secaucus Junction and Newark Penn Station. Approaching the Hudson River, the highway uses the New Jersey Meadowlands approaches and connects to the Holland Tunnel toll plaza at the West Side Highway/12th Avenue corridor in Manhattan, providing direct access to Battery Park City, Chelsea (Manhattan), and the Financial District, Manhattan.

History

The corridor that became I-78 follows historic turnpikes and freight routes used during the 19th century, including alignments near the Northampton County canals and the Lehigh Coal & Navigation Company transportation network. Planning for the route was codified under the Federal-Aid Highway Act of 1956 with routing influenced by regional industrial centers such as Bethlehem Steel Corporation and distribution points serving the Port of New York and New Jersey. Construction milestones included early completions in eastern Pennsylvania to serve the Allentown-Bethlehem-Easton metropolitan area and subsequent segments across New Jersey built in stages during the 1960s and 1970s, coordinated with agencies like the New Jersey Department of Transportation and the Pennsylvania Department of Transportation. Environmental and urban controversies shaped alignments near Phillipsburg, Easton, and the Meadowlands, drawing involvement from groups including the Sierra Club and local civic coalitions. The approach to Manhattan employed existing Hudson River crossings planning debates with the Port Authority of New York and New Jersey, culminating in the highway’s connection to the Holland Tunnel complex and integration with New York City Department of Transportation routes.

Major intersections

I-78’s principal junctions include an interchange with Interstate 81 near Harrisburg connections, a cross with Interstate 476 serving the Northeast Extension of the Pennsylvania Turnpike, and intersections with U.S. Route 22 (US 22) and U.S. Route 209 (US 209) in eastern Pennsylvania. In New Jersey, key interchanges are with Interstate 287 in Bridgewater Township, New Jersey, U.S. Route 202 (US 202) in Somerville, New Jersey, Interstate 95/New Jersey Turnpike near Newark, and U.S. Route 1/9 (US 1/9) providing access to port facilities and the Pulaski Skyway corridor. The eastern terminus interfaces with approaches to the Holland Tunnel and merges with vehicular arterials feeding Manhattan and the West Side Highway system.

Future developments

Planned and proposed projects affecting the corridor include interchange modernizations overseen by the New Jersey Turnpike Authority and pavement rehabilitation programs by the Pennsylvania Department of Transportation and New Jersey Department of Transportation. Freight capacity initiatives tie into regional investments at the Port of New York and New Jersey and rail–road intermodal projects with entities such as Conrail and CSX Transportation. Environmental mitigation and resilience efforts, motivated by events involving Hurricane Sandy impacts on regional infrastructure, have generated proposals for floodproofing, stormwater upgrades, and bridge deck replacements, coordinated with the Federal Highway Administration and state transportation agencies. Multimodal planning links to commuter rail improvements by NJ Transit and transit-oriented development near major interchanges in Somerset County, New Jersey.

Auxiliary routes

Auxiliary routes associated with the corridor include spur and loop designations in the regional I‑systems such as connections to Interstate 278 via surrounding urban networks, and state-numbered freeways and parkways providing radial access to urban cores like Newark Liberty International Airport and Jersey City, New Jersey. Local and regional bypasses managed by counties like Hunterdon County, New Jersey and municipalities including Union Township, New Jersey function as connectors between the mainline and business districts, while historic alignments persist as portions of U.S. Route 22 (US 22) and county routes serving local traffic.

Category:Interstate Highways in the United States Category:Transportation in Pennsylvania Category:Transportation in New Jersey Category:Transportation in New York City