I-78 — LLMpedia

I-78
Country	United States
Type	Interstate
Route	78
Length mi	139.58
Established	1957
Direction a	West
Terminus a	Union Township, Lebanon County, Pennsylvania
Direction b	East
Terminus b	Newark, New Jersey
States	Pennsylvania, New Jersey

Contents

I-78 is a major east–west Interstate corridor in the northeastern United States connecting the Susquehanna River watershed and the Lehigh Valley with the New York metropolitan area, the Port Newark–Elizabeth Marine Terminal, and the Holland Tunnel. The route serves as a freight and commuter artery passing through key nodes such as Allentown, Pennsylvania, Easton, Pennsylvania, Phillipsburg, New Jersey, Somerset County, New Jersey, Union Township, New Jersey, and Newark, New Jersey. It links to principal highways including Interstate 81, Interstate 287, Interstate 95, and U.S. Route 22 while interfacing with rail corridors like the Lehigh Valley Railroad and the Conrail Shared Assets network.

Route description

The highway begins near Lebanon County, Pennsylvania at an interchange with U.S. Route 22 and proceeds east across the Pennsylvania Dutch Country and the Lehigh River valley toward Allentown, Pennsylvania and Bethlehem, Pennsylvania. In the Lehigh Valley it parallels the historic alignment of the Lehigh and Hudson River Railway and intersects Interstate 476 and business routes that serve Reading, Pennsylvania and Pennsburg, Pennsylvania. Crossing into New Jersey via the Delaware River, the route traverses Phillipsburg, New Jersey and follows the Musconetcong River corridor, passing near Clinton, New Jersey, Somerville, New Jersey, and the Watchung Mountains. In central New Jersey the highway forms part of the regional feeder system to Newark Liberty International Airport and the Port of New York and New Jersey, meeting Interstate 287 and Interstate 95 before descending the New Jersey Meadowlands into Newark, New Jersey, where it terminates at the Holland Tunnel approaches and regional arterial streets including New Jersey Route 21 and local connectors to U.S. Route 1/9.

The corridor traces antecedents to 19th-century turnpikes and canals such as the Lehigh Canal and the Belvidere Delaware Railroad that supported anthracite coal and manufactured goods distribution to the New York Harbor. As part of the original 1956 Interstate program, the route was designated in 1957 to link the Scranton–Wilkes-Barre metropolitan area region with Newark, New Jersey and New York City. Construction proceeded in segments through the 1960s and 1970s, with major projects coordinated by the Pennsylvania Department of Transportation and the New Jersey Department of Transportation. Notable engineering undertakings included river crossings over the Delaware River with interstate bridge collaborations involving the Delaware River Joint Toll Bridge Commission and complex interchanges near Easton, Pennsylvania and Somerset County, New Jersey. The corridor has been shaped by freight shifts influenced by the rise of Port Newark–Elizabeth Marine Terminal and rail consolidations such as Conrail formation, and by regional planning debates featuring the Port Authority of New York and New Jersey and county agencies over tolling, capacity, and environmental impacts in the Watchung Reservation and Meadowlands.

Major interchanges connect the corridor to interstate and U.S. highways, rail terminals, and ports. Significant junctions include the western intersection with U.S. Route 22 and access to Interstate 81 via regional links; the connection with Interstate 476 near Lehigh County; the crossing with Interstate 287 in central New Jersey providing circumferential access to Middlesex County, New Jersey and Bergen County, New Jersey; the tie-ins to U.S. Route 1/9 near Newark, New Jersey for freight routes to Port Newark–Elizabeth Marine Terminal; and the eastern terminals that facilitate traffic to the Holland Tunnel and Manhattan, New York City. Interchanges with state routes such as New Jersey Route 31, New Jersey Route 12, and New Jersey Route 24 serve regional centers including Clinton, New Jersey, Lebanon, New Jersey and Morristown, New Jersey.

Service facilities along the corridor include private travel plazas, truck stops, and logistics hubs near Allentown, Pennsylvania, Phillipsburg, New Jersey, and Somerset County, New Jersey. Rest and fueling facilities are concentrated at interchanges with high freight density near the New Jersey Turnpike approaches and industrial parks serving Port Newark–Elizabeth Marine Terminal, Newark Liberty International Airport, and inland distribution centers that evolved from sites such as the Lehigh Valley Industrial Park. Tolls are collected on nearby tolled facilities managed by agencies like the Delaware River Port Authority and the New Jersey Turnpike Authority, though the Interstate mainline itself is largely untolled except where it uses tolled crossings administered by regional bridge commissions. Commercial vehicles frequently encounter weigh stations operated by the New Jersey Motor Vehicle Commission and the Pennsylvania Department of Transportation.

Planning initiatives by metropolitan planning organizations such as the Lehigh Valley Planning Commission, the North Jersey Transportation Planning Authority, and the Port Authority of New York and New Jersey have proposed capacity upgrades, interchange reconstructions, and freight-oriented improvements to better connect inland intermodal yards with Port Newark–Elizabeth Marine Terminal and Newark Liberty International Airport. Proposals include targeted widening near choke points at Somerset County, New Jersey and bridge rehabilitations over the Delaware River coordinated with the Delaware River Joint Toll Bridge Commission. Environmental mitigation projects aim to reduce runoff impacting the Watchung Reservation and Raritan River watershed, while freight efficiency plans coordinate with rail projects involving NJ Transit and Conrail Shared Assets to shift long-haul cargo from trucks to rails. Funding discussions have invoked federal programs such as the Infrastructure Investment and Jobs Act and state bond measures in Pennsylvania and New Jersey.

The route's exits serve urban, suburban, and rural nodes from western terminus interchanges with U.S. Route 22 through successive exits for Interstate 476, Pennsylvania Route 309, county roads serving Allentown, Pennsylvania and Bethlehem, Pennsylvania, then New Jersey exits for New Jersey Route 173 at Phillipsburg, New Jersey, New Jersey Route 31 at Clinton, New Jersey, U.S. Route 202 and New Jersey Route 28 near Somerville, New Jersey, continuing east to connections with Interstate 287, New Jersey Route 24 and U.S. Route 1/9 before terminating at approaches to the Holland Tunnel and arterial connections into Newark, New Jersey and the New York City region.