Interstate 78

Interstate 78 (I-78) is an east–west Interstate Highway spanning 145.34 miles (233.84 km) across the Northeastern United States, connecting its western terminus at an interchange with Interstate 81 in Union Township, Lebanon County, Pennsylvania—northeast of Harrisburg—to its eastern terminus at Canal Street in Lower Manhattan, New York City, via the Holland Tunnel.^[1][2] The route primarily follows a corridor through Pennsylvania (77.50 miles), New Jersey (67.83 miles), and a brief 0.5-mile segment in New York, providing a key nontolled alternative to the Pennsylvania and New Jersey Turnpikes for regional travel.^[3][4] In Pennsylvania, I-78 begins at the I-81 interchange and heads eastward through rural and suburban landscapes in Lebanon, Berks, Lehigh, and Northampton counties, intersecting U.S. Route 22 near Allentown and crossing the Lehigh River before reaching the Delaware River at Easton.^[3] The highway facilitates significant freight movement, with an average annual daily traffic of over 51,000 vehicles, including substantial truck volumes that support commerce between central Pennsylvania and the New York metropolitan area.^[3][5] Entering New Jersey via the I-78 Toll Bridge over the Delaware River, the route continues 67.83 miles eastward, passing through Warren, Hunterdon, Somerset, Union, Essex, and Hudson counties, with connections to major roadways like Interstate 287 and U.S. Route 22.^[4] It serves urban centers such as Phillipsburg, Clinton, Somerville, Newark, and Jersey City, where it approaches the Hudson River and enters the Holland Tunnel— a dual-tube underwater crossing operated by the Port Authority of New York and New Jersey that carries I-78 under the river to Manhattan.^[4][2] In New York, the designated I-78 segment is limited to the short approach on the Manhattan side, terminating amid the dense infrastructure of Lower Manhattan.^[2] Designated as part of the Interstate System in 1957, I-78 was largely completed by the late 1980s, with its development relieving congestion on parallel U.S. highways and enhancing economic ties across the Delaware Valley and New York City regions.^[1] Today, it remains a critical artery for over 3.8 million daily vehicle-miles in Pennsylvania alone, underscoring its role in supporting industrial, commercial, and commuter traffic in one of the nation's most densely populated corridors.^[3]

Overview

Route summary

Interstate 78 (I-78) is an east–west Interstate Highway spanning 146.28 miles (235.41 km) across Pennsylvania, New Jersey, and New York, serving as a key corridor for regional travel and commerce in the northeastern United States.^[6] The route begins at its western terminus with an interchange at Interstate 81 (I-81) in Union Township, Lebanon County, Pennsylvania, and extends eastward to its eastern terminus at the entrance plaza of the Holland Tunnel in Manhattan, New York City.^[7][2] Designated as part of the National Highway Freight Network, I-78 facilitates the movement of goods by accommodating over 4 million trucks annually, supporting freight transport from inland areas to major ports.^[8] In Pennsylvania, the highway covers 77.95 miles (125.50 km), traversing from the I-81 interchange near Fredericksburg across the Delaware River via the I-78 Toll Bridge near Phillipsburg.^[9] The New Jersey segment measures 67.83 miles (109.16 km), continuing from the toll bridge in Phillipsburg eastward through the northern part of the state to the Newark Bay–Hudson River waterfront near Jersey City.^[4] In New York, I-78 consists of a short 0.50-mile (0.80 km) stub that passes through the Holland Tunnel beneath the Hudson River and terminates at Canal Street in Lower Manhattan.^[10] The corridor connects major urban centers such as Allentown in Pennsylvania and Newark in New Jersey, providing an alternative to tolled routes like the Pennsylvania and New Jersey Turnpikes for east–west travel.^[6]

Significance and traffic

Interstate 78 functions as a vital east-west transportation corridor, linking the industrial Lehigh Valley region in eastern Pennsylvania—home to major manufacturing and distribution hubs—with the densely populated New York City metropolitan area. This connection supports efficient movement of both passengers and goods across the Northeast, bridging rural and suburban areas in central Pennsylvania with urban centers in New Jersey and New York. The route parallels key rail lines like the Raritan Valley Line and integrates with broader interstate systems, handling significant daily traffic.^[11] The highway plays a critical role in freight movement, serving as a primary link between Lehigh Valley warehouses and distribution centers and major ports such as Port Newark and Port Elizabeth, which handle substantial container traffic. It accommodates significant volumes of cargo, with key commodities including manufactured products, food, and construction materials, underscoring its importance to the regional supply chain. Truck traffic accounts for 20 to 30 percent of overall volumes, reflecting the corridor's heavy reliance on highway freight to support e-commerce growth and industrial activities in the Lehigh Valley.^[12][11] Traffic volumes on Interstate 78 are among the highest in the region, with average annual daily traffic (AADT) exceeding 130,000 vehicles in urban sections near Newark. Truck percentages reach up to 25 percent in high-freight sections, such as those east of Interstate 95, where average daily truck volumes exceed 37,000 as of 2023. These patterns highlight the route's dual role in commuter travel and logistics.^[13][12] As a toll-free alternative to Interstate 80 in Pennsylvania, Interstate 78 allows drivers to bypass the Pennsylvania Turnpike's fees while providing access to eastern destinations, appealing to cost-conscious commuters and truckers. In New Jersey, its eastern segment in the Newark area becomes the tolled New Jersey Turnpike Newark Bay-Hudson County Extension from near Interchange 14 to the Holland Tunnel, enabling seamless integration with the tolled system for continued travel toward New York City.^[14][15]

Route description

Pennsylvania

Interstate 78 begins in Pennsylvania at a trumpet interchange with Interstate 81 in Union Township, Lebanon County, near the community of Lickdale. From this western terminus, the highway proceeds eastward through rural areas of Lebanon and Berks counties, characterized by rolling farmland and forested hills, while bypassing the city of Reading to the south. This initial segment traverses lightly developed landscapes, providing a direct route for through traffic avoiding local urban congestion.^[6][7] Near Fredericksburg in Lebanon County, Interstate 78 joins a 43-mile concurrency with U.S. Route 22, forming a major east-west corridor that continues into Lehigh County. Along this overlap, the route expands to six lanes in places to handle increased volume, bypassing Allentown to the south via a 7-mile section (exits 53 to 60) concurrent with PA 309 that skirts the city's southern areas. Here, I-78 crosses the Lehigh River on a multi-span bridge, transitioning into more varied terrain with occasional elevation changes before entering Northampton County near Bethlehem.^[7][6] Within Northampton County, the highway maintains its eastward alignment through suburban and semi-rural zones, incorporating truck climbing lanes in hilly sections to facilitate safer passage for commercial vehicles navigating the Appalachian foothills. The route concludes its 77.50-mile length in Pennsylvania at the Delaware River, where it crosses the I-78 Toll Bridge—a four-lane structure managed by the Delaware River Joint Toll Bridge Commission—into Phillipsburg, New Jersey.^{[7][3][15][16]}

New Jersey

Interstate 78 enters New Jersey from Pennsylvania across the Delaware River via the I-78 Toll Bridge, a 1,222-foot-long structure connecting Williams Township in Northampton County, Pennsylvania, to Phillipsburg in Warren County, New Jersey.^[15] The bridge, opened in 1989, features a one-way toll plaza on the Pennsylvania side with seven lanes for westbound collection and includes a rest area and welcome center nearby.^[15] Upon entering New Jersey at milepost 0.00, I-78 proceeds eastward as a freeway through rural portions of Warren and Hunterdon Counties, passing near Clinton where it begins to encounter suburban development.^[4] The route then transitions into more developed areas around Somerville in Somerset County, intersecting with major connectors like the Vincent R. Kramer Interchange at I-287 near milepost 29.^[4] Continuing east, I-78 traverses the Watchung Mountains through a rock cut in Union and Essex Counties, a significant engineering feature that facilitates passage through the hilly terrain while minimizing environmental impact on nearby reservations.^[17] The freeway widens into a local-express lane configuration as it enters the urban core of Essex County, serving Newark with connections to I-95 and the New Jersey Turnpike.^[4] In this densely populated region, I-78 assumes the Newark Bay-Hudson County Extension of the New Jersey Turnpike, featuring a toll plaza near milepost 53.16 and the Alexander Hamilton Service Area in Secaucus, Hudson County, which provides amenities for travelers between turnpike interchanges 15E and 16E.^[18][19] The route culminates in Hudson County, crossing the Newark Bay Bridge—a toll facility opened in 1956 that spans Newark Bay to Bayonne—before reaching the Holland Tunnel approach at the New York state line near milepost 67.83.^[18] This final segment, under the jurisdiction of the New Jersey Turnpike Authority from approximately milepost 58.58 onward, includes another toll plaza near milepost 64.05 and serves as a vital link for trans-Hudson traffic.^[4] Overall, I-78 spans 67.83 miles across New Jersey, traversing Warren, Hunterdon, Somerset, Union, Essex, and Hudson Counties from the Delaware River to the Hudson River.^[4]

New York

Interstate 78 enters New York via the Holland Tunnel, a vehicular crossing under the Hudson River that connects Jersey City, New Jersey, to Lower Manhattan.^[2] The tunnel, managed by the Port Authority of New York and New Jersey, emerges in Manhattan at Canal Street, where I-78 briefly continues eastward.^[6] This segment serves as the eastern terminus of the interstate, providing direct access to the urban core of New York City. The New York portion of I-78 spans just 0.50 miles and is largely unsigned due to the dense urban environment and space constraints in Manhattan, which preclude standard interstate signage.^[6] Upon exiting the tunnel, the route follows a short, unsigned alignment along West Street, cosigned as New York State Route 9A (NY 9A), before reaching its official end at an exit rotary near the intersection with Laight and Canal Streets.^[6] This brief stretch integrates I-78 into the local street network, with ramps providing connections to nearby arterials such as Hudson Street, Varick Street, and Beach Street, facilitating primarily local access to Lower Manhattan rather than through-traffic.^[6] Originally, plans called for extending I-78 eastward from the Holland Tunnel through Manhattan, Brooklyn, Queens, and into the Bronx to connect with the Bruckner Interchange, where it would meet Interstates 95, 278, 295, and 678.^[6] However, these extensions were canceled in the 1970s amid community opposition and shifting urban planning priorities, leaving the current stub as a limited connector focused on regional entry rather than a full crosstown route.^[6] Travelers entering New York via I-78 through the Holland Tunnel encounter tolls collected only in the New York-bound direction. As of November 2025, the toll for passenger vehicles with E-ZPass is $16.06 during peak hours (weekdays 6-10 a.m. and 4-8 p.m., weekends 11 a.m.-9 p.m.) and $14.06 off-peak, with the Port Authority overseeing all collections through cashless tolling systems.^[20]

Major junctions

Key interchanges in Pennsylvania

Interstate 78 in Pennsylvania features 20 numbered exits spanning its 78-mile length from the I-81 interchange to the New Jersey state line, with designs ranging from simple diamond interchanges in rural areas to more complex partial cloverleaf configurations in suburban zones to accommodate higher traffic volumes.^[21] The western terminus at Exit 1 connects to Interstate 81 via a directional T interchange at milepost 0 in Union Township, Lebanon County, facilitating seamless access from I-81 north to Hazleton (56 miles) and south to Harrisburg (23 miles) while integrating a partial ramp for local traffic to PA 72 and Lebanon.^[6] This design minimizes weaving and supports the route's role as a connector between central Pennsylvania and the Lehigh Valley.^[6] A significant concurrency with U.S. Route 22 begins near Fredericksburg in Lebanon County and extends eastward through the Lehigh Valley to the New Jersey state line near Phillipsburg, enhancing connectivity for through traffic from western Pennsylvania to the New York City region via a shared six-lane freeway alignment.^[6] In the Allentown vicinity, key interchanges include Exit 60 with PA 309 in South Whitehall Township, a partial cloverleaf design that provides direct southbound access to Quakertown and ties into the Pennsylvania Turnpike (I-476) toll road, handling substantial volumes with an average annual daily traffic (AADT) of approximately 63,459 vehicles on adjacent segments.^[6][22] Nearby, Exit 49A at Summit Street in Upper Macungie Township uses a partial cloverleaf interchange to connect to PA 100 south toward Trexlertown, serving industrial parks and local commuters in a suburban setting with controlled acceleration and deceleration lanes.^[21][6] Further west, Exit 30 near Hamburg in Berks County stands out as a high-volume diamond interchange, supporting over 44,000 vehicles daily and linking to secondary routes toward Reading while bridging rural and semi-urban traffic flows.^[21][22] At the eastern end, Exit 75 integrates the I-78 Toll Bridge crossing into New Jersey, featuring a toll plaza with E-ZPass lanes immediately west of the Delaware River in Williams Township, Northampton County, designed for efficient collection from eastbound traffic heading to Phillipsburg and beyond.^[15] This setup, managed by the Delaware River Joint Toll Bridge Commission, includes barrier-separated lanes to handle peak cross-state volumes exceeding 58,000 vehicles per day on nearby segments.^[22][15]

Key interchanges in New Jersey

Interstate 78 enters New Jersey from Pennsylvania via the I-78 Toll Bridge over the Delaware River, with no numbered exit immediately at the state line in Phillipsburg, Warren County. The first interchange occurs at Exit 3 (milepost 3.42), a grade-separated diamond providing access to NJ 173 toward Alpha Borough and Phillipsburg, serving local traffic in the rural western portion of the route. This entry point facilitates the transition from Pennsylvania's more rural alignments into New Jersey's denser network, handling cross-state commuter and freight movement without an initial off-ramp to minimize disruptions at the border.^[4] In the central section, Exit 29 (milepost 30.32) stands out as the Vincent R. Kramer Interchange, a directional cloverleaf connecting I-78 to I-287 in Bedminster and Bridgewater Townships, Somerset County. This junction links I-78's east-west corridor to I-287's circumferential route around New York City, acting as a critical bypass for through traffic and a major hub for freight distribution in the region, with ongoing improvements to enhance ramp flow and safety. Further east, Exit 36 (milepost 36.15) in Warren Township provides access to King George Road (CR 651), near the PA 31 parallel in adjacent Pennsylvania areas, and has been targeted for widening projects to alleviate congestion in high-traffic suburban zones.^[4][23][24] Approaching Newark, the route features key urban interchanges, including Exit 57 (milepost 57.44) for US 1-9 in Newark, Essex County, configured as a trumpet interchange for southbound access toward the Pulaski Skyway and Port Newark. Immediately following is Exit 58 (milepost 58.02), a complex multi-level stack interchange with the New Jersey Turnpike (I-95), integrating local lanes with the tolled mainline to manage high-volume flows to Newark Liberty International Airport and beyond; this is often referenced in traffic studies as Exit 60 in broader Turnpike contexts due to its positioning near milepost 60. I-78 in New Jersey includes 35 numbered exits overall, with these Newark-area junctions handling significant daily volumes exceeding 100,000 vehicles.^[4][25] East of Newark, I-78 transitions to the tolled Newark Bay Extension at the Exit 58 interchange, crossing the Newark Bay Bridge (also known as the Vincent R. Casciano Memorial Bridge) with a toll plaza near milepost 62, providing no dedicated exit for the bridge itself but serving as a vital link to Hudson County. The first post-bridge interchange is Exit 14A (milepost 62.01) for Linden Avenue (CR 602) in Jersey City, followed by Exit 14B (milepost 63.90) for Bayview Avenue. The eastern terminus approaches the Holland Tunnel via an uncontrolled merge into local streets in Jersey City, where I-78 yields to at-grade connections without a numbered exit, directing traffic directly into the tunnel portal maintained by the Port Authority of New York and New Jersey.^[4]

Key interchanges in New York

In New York, Interstate 78 (I-78) maintains its limited-access freeway status for only about 0.5 miles east of the New Jersey state line, entering via the Holland Tunnel before terminating in Lower Manhattan. Unlike the extensive numbered exit system in New Jersey and Pennsylvania, the New York segment features no traditional interstate-style interchanges along its brief length; instead, primary access is provided through the tunnel's eastbound exit plaza in Manhattan, which funnels traffic into a traffic circle at Canal Street. This plaza includes five sequentially numbered exits (1 through 5) arranged counterclockwise, serving as the sole direct entry and exit points for the route in the state.^[26] Exit 1 connects directly to NY 9A (West Street) northbound, providing immediate access to the West Side Highway corridor, while the connection at Canal Street itself operates as a signalized at-grade intersection, integrating I-78 traffic with local urban streets. Exits 2 and 4 serve uptown and downtown Manhattan via Hudson Street and Broome/Varick Streets, respectively, and Exit 5 leads onto Canal Street eastbound for further distribution into the city grid. Although not directly interchanged, a link to I-278 (Brooklyn-Queens Expressway) exists via nearby ramps from Exit 3 (to Brooklyn via the Manhattan Bridge approach), allowing indirect connectivity for through traffic heading eastward, though this requires navigating surface streets.^[26][27] The urban constraints of Lower Manhattan contribute to significant challenges at these access points, including chronic congestion from the convergence of local, commuter, and tourist traffic, exacerbated by the tunnel's role as a major Hudson River crossing with average eastbound crossing times often exceeding 10 minutes during peak periods. No additional interchanges have been constructed since the 1970s, following the official cancellation of planned extensions like the Lower-Manhattan Expressway on March 24, 1971, by Governor Nelson Rockefeller, which had aimed to extend I-78 across the island but was halted due to community opposition and environmental concerns.^[2][28]

Auxiliary routes

Active and former spurs

Although no auxiliary or spur routes branch directly from the current alignment of Interstate 78, several active auxiliary routes are designated in the New York City area as child interstates of I-78. These include Interstate 278 (I-278), which follows the Gowanus Expressway in Brooklyn and the Bruckner Expressway in the Bronx; Interstate 678 (I-678), the Van Wyck Expressway serving John F. Kennedy International Airport; and Interstate 878 (I-878), the short Nassau Expressway in Queens. These routes were planned to connect to I-78 via its unbuilt eastern extension through Lower Manhattan but remain designated as auxiliaries despite the truncation of I-78 at the Holland Tunnel.^[6] Interstate 78 has no other active auxiliary or spur routes designated as Interstate highways along its primary east-west corridor across Pennsylvania, New Jersey, and New York, with the parent route serving without any full child interstates branching directly from it.^[6] The only former spur associated with I-78 is Interstate 378, a short freeway in Bethlehem, Pennsylvania, that originally connected the Lehigh Valley Thruway (US 22) near Lehigh Valley International Airport to downtown Bethlehem. Constructed from 1966 to 1968 at a cost reflecting early Interstate standards, I-378 spanned 3.34 miles and opened to traffic in 1968 as a designated spur of the planned I-78 alignment along US 22.^[29][30] Its purpose was to facilitate access to central Bethlehem for local and regional traffic prior to the completion of the full I-78 freeway.^[29] Following the 1960s decision to reroute I-78 onto a new southern alignment bypassing the Lehigh Valley urban core, I-378 became disconnected from the Interstate system. The American Association of State Highway and Transportation Officials (AASHTO) eliminated the I-378 designation on June 30, 1970, and the route was renumbered as Pennsylvania Route 378 in 1971, incorporating it into a longer 9.55-mile state highway extending south to PA 309 in Upper Saucon Township.^[29][31] Known locally as the Bethlehem Spur or Eighth Street Expressway, the former I-378 segment now provides urban freeway access, with its Interstate signage removed shortly after decommissioning in the early 1970s; the roadway remains maintained by PennDOT as a state route for local connectivity.^[32][29] Although not an official auxiliary, Pennsylvania Route 33 acts as a de facto northern bypass for I-78 through the Pennsylvania portion of the Lehigh Valley, interchanging with I-78 near Easton and extending 27.7 miles northwest to I-80 west of Stroudsburg to alleviate congestion around the Allentown-Bethlehem area.^[33][7] This freeway connection, completed in phases through the 2000s, supports through-traffic paralleling the more urban I-78 corridor.^[34]

Planned or canceled extensions

Several proposals for extensions and auxiliary routes of Interstate 78 were developed during the mid-20th century but ultimately canceled due to environmental opposition, community concerns, and shifting priorities. One such plan was Interstate 178 (I-178), a proposed 2-mile spur from I-78 into downtown Allentown, Pennsylvania, first announced in 1954 by the Pennsylvania Department of Highways. Intended to connect the Lehigh Valley Thruway (US 22/I-78) to Center City Allentown, the route faced significant local opposition in the late 1960s and early 1970s, particularly because it would have passed through the site of the Liberty Bell Shrine (now the Liberty Bell Museum), leading to its cancellation in 1971. Environmental concerns and perceived low traffic demand further contributed to the decision against construction.^[35] In New York, an ambitious 13-mile extension of I-78 was planned from the Holland Tunnel eastward through Lower Manhattan, Brooklyn, and Queens to the Bruckner Interchange (I-278/I-95) in the Bronx, incorporating the controversial Lower Manhattan Expressway (LOMEX). Approved as part of the Interstate system in 1960, the project aimed to alleviate congestion but encountered fierce resistance from urban planners, residents, and figures like Jane Jacobs over its potential to disrupt historic neighborhoods, increase air pollution, and elevate carbon monoxide levels. Governor Nelson Rockefeller officially canceled the unbuilt segments, including LOMEX, in March 1971 as part of a broader $695.2 million highway improvement package that prioritized other infrastructure.^[36] Another unbuilt proposal emerged in the 1960s and 1970s for a southern bypass of I-78 around Allentown, Pennsylvania, which would have branched off near Adams Road in Upper Macungie Township, curved south through Vera Cruz, and rejoined near Lanark to avoid the city's core. This alternative route was debated amid concerns over congestion on US 22 but faced lawsuits from groups like the Saucon Association for a Viable Environment and the Environmental Defense Fund, citing inadequate environmental reviews and potential damage to Saucon Park, farmland, and rural communities in Upper Milford and Salisbury Townships. High costs, noise pollution, and air quality impacts led to its rejection in favor of upgrading the existing PA 309 corridor; the project was scaled back and finalized without the bypass by 1983.^[37] As of the 2020s, no active plans exist for new extensions of I-78, with state transportation agencies focusing instead on maintenance, pavement preservation, and limited widening projects along the existing corridor. For instance, the Pennsylvania Department of Transportation has studied minor expansions for capacity but prioritized rehabilitation over route extensions due to environmental regulations and funding constraints. Similarly, the New Jersey Turnpike Authority's ongoing $10.7 billion rebuild of the I-78 Turnpike Extension emphasizes bridge replacements and lane additions within current alignments, without proposals to extend beyond the Holland Tunnel.^[38][39]

History

Planning and construction phases

Interstate 78 was designated as part of the Interstate Highway System through the Federal-Aid Highway Act of 1956, which authorized the construction of 41,000 miles of limited-access highways nationwide, including an initial planned length of approximately 145 miles for I-78 from central Pennsylvania to New York City.^[40][1] The route's alignment received federal approval in the late 1950s, with state transportation departments in Pennsylvania, New Jersey, and New York coordinating on route selections to connect existing highways like U.S. Route 22 and the Holland Tunnel while avoiding urban congestion where possible.^[41] In Pennsylvania, construction began in the late 1950s, with early segments between exits 23 and 30 opening to traffic in 1958 as part of the broader Interstate push following the 1956 act. Much of the route west of Allentown utilized upgrades to the pre-Interstate Lehigh Valley Thruway along U.S. Route 22, completed in the mid-1950s. Progress accelerated in the 1960s, focusing on the corridor from I-81 near Harrisburg eastward through the Lehigh Valley, though environmental reviews and land acquisition delayed some sections. The Allentown bypass, a key segment skirting the city's downtown to improve freight access, was constructed starting in 1984 and opened on November 21, 1989.^[42] The full length in Pennsylvania, from the I-81 interchange in Union Township to the New Jersey state line near Easton, was completed on November 21, 1989, marking the end of major construction in the state.^[1][7] Construction of I-78 in New Jersey, known during planning as the Phillipsburg–Newark Expressway, spanned the 1960s through the 1980s, integrating pre-existing infrastructure like the Newark Bay Bridge. The bridge, part of the New Jersey Turnpike's Newark Bay Extension, was completed in 1956 to carry four lanes across the bay and later incorporated into I-78's alignment for seamless connectivity to the Holland Tunnel.^[43] Major building phases included the western sections from Phillipsburg eastward in the early 1960s, with expansions and interchanges added through the 1970s; the final 5.5-mile "missing link" through the Watchung Reservation between Springfield and Scotch Plains, featuring extensive environmental mitigation including wildlife crossings, opened in August 1986 after federal and state approvals emphasized wetland preservation and noise barriers.^[43][44] The 67-mile New Jersey portion reached full operational status by 1989, linking rural Warren County to urban Essex County. In New York, the route's short 0.5-mile segment consists primarily of the Holland Tunnel, a pre-Interstate structure opened on November 13, 1927, to provide vehicular access under the Hudson River from Jersey City to Manhattan.^[45] The tunnel received its I-78 designation in the early 1960s as part of system-wide numbering approved by the Federal Highway Administration, with minor approach road improvements and signage completed in the 1970s to integrate it fully into the Interstate network.^[41] Key milestones included the opening of the I-78 Toll Bridge over the Delaware River on November 21, 1989, connecting the Pennsylvania and New Jersey sections at a cost of approximately $100 million for the structure itself, financed through toll revenues and federal aid.^[15] Overall project costs for I-78, estimated in the 1960s at around $500 million, escalated due to inflation, environmental compliance, and urban complexities, reaching roughly $2 billion by completion in the early 1990s when adjusted for modern dollars.^[42]

Controversies and community impacts

The construction of Interstate 78 in the 1960s through Newark, New Jersey, resulted in significant community displacement, particularly in the Weequahic neighborhood, where the highway's path razed hundreds of homes and small businesses, displacing at least 5,000 residents overall for the combined I-78 and I-280 projects.^[46] This demolition fragmented stable, racially integrated middle-class areas, exacerbating racial and economic divides as the fourteen-lane corridor isolated Weequahic from adjacent suburbs and contributed to the exodus of white residents from the city.^[47] The Ironbound neighborhood, while not the primary focus of I-78's path, experienced indirect pressures from the broader highway network's expansion, which closed hundreds of local businesses and uprooted working-class families in multi-ethnic communities.^[48] In Pennsylvania's Lehigh Valley during the 1970s, intense local opposition to I-78's alignment sparked the "I-78 or anti-78" debate, centered on fears of farmland loss, increased noise pollution, and environmental degradation from what critics dubbed a "concrete snake" encroaching on verdant foothills south of Allentown and Bethlehem.^[49] Residents and farmers, bolstered by the passage of State Act 100 in the late 1970s—which prioritized agricultural land preservation—pushed for alternative routes and mass transit options to mitigate sprawl, traffic congestion, and the destruction of productive farmland in Northampton and Lehigh Counties.^[50] A pivotal seven-hour public hearing in 1971 examined multiple alignment proposals, highlighting community concerns over the highway's potential to irreversibly alter rural landscapes and amplify noise in residential areas near the proposed path.^[51] Environmental challenges in New Jersey's Warren County during the late 1960s and 1970s focused on the highway's potential wetland destruction, prompting opposition under the newly enacted National Environmental Policy Act (NEPA) of 1970, which required environmental impact assessments for federal projects.^[52] Residents and environmental groups contested plans that would traverse sensitive ecological areas, arguing that the route threatened local wetlands and habitats; this led to studies and delays as state and federal agencies evaluated mitigation measures to comply with NEPA's mandates for minimizing irreversible environmental harm.^[53] These controversies yielded partial reroutings in New Jersey, such as the 1968 decision to bypass downtown Phillipsburg in Warren County following resident protests, which shifted the alignment southward to avoid direct urban incursion and preserved small towns like Alpha.^[53] Community relocation programs were implemented during construction, providing assistance to displaced Newark families, but they often fell short, resulting in long-term urban decay, concentrated poverty, and persistent neighborhood fragmentation in affected areas like Weequahic.^[54] In Pennsylvania, the debates influenced zoning reforms and farmland preservation efforts, though the highway's eventual path still led to notable losses of agricultural land and ongoing community adjustments to increased noise and development pressures.^[49]

Incidents and safety

Notable accidents

One of the earliest major incidents on Interstate 78 was a snow squall-induced pileup on December 2, 2002, in the Pennsylvania section near the Berks-Lehigh county line west of Fogelsville. The sudden weather event reduced visibility to near zero, leading to collisions involving at least 60 vehicles, with a significant cluster of about 30 cars near Route 863 and scattered crashes extending further. Numerous people were injured, including a boy with a forehead cut, and the highway was closed for over two hours in the Lehigh Valley area to allow for rescue operations and debris clearance by state police and emergency services.^[55] A significant tanker crash occurred on December 6, 2014, on I-78 in Union, New Jersey, near the Newark area. A fuel tanker carrying 9,000 gallons collided with an Audi sedan and a tractor-trailer hauling mulch, igniting an explosion that engulfed all three vehicles in flames and caused a major fuel spill. The immediate response involved the Union County Foam Team extinguishing the blaze in 15 minutes, while lanes were closed for hours to manage the fire and hazardous materials; one driver was killed, but no other fatalities occurred.^[56][57] On March 28, 2023, a multi-vehicle crash disrupted traffic on I-78 eastbound near Exit 49B in Springfield, Union County, New Jersey. The incident involved a dump truck, a tractor-trailer, and a pickup truck, resulting in the death of the dump truck driver and injuries to others in a fiery collision. Emergency responders closed lanes in both directions for several hours to treat the injured and clear the scene.^[58][59] In December 2024, a tractor-trailer crash in Upper Saucon Township, Lehigh County, Pennsylvania, killed two people when two tractor-trailers and another vehicle collided, closing lanes of I-78 westbound.^[60] On November 7, 2024, two men were killed in Warren Township, New Jersey, when struck by a vehicle while changing a tire on their van on the shoulder of I-78 westbound near milepost 38.7.^[61] Accidents on I-78 often involve commercial vehicles due to the route's role as a key freight corridor.

Safety improvements and statistics

Interstate 78 sees a high volume of reportable crashes, with concentrations in urbanized areas of New Jersey, particularly around interchanges, due to traffic volumes exceeding 100,000 vehicles per day in peak sections. These incidents often involve rear-end collisions and truck-related events.^[62][63] Statewide fatality rates in New Jersey and Pennsylvania have declined in recent years, with enhancements like improved signage and enforcement contributing to safety on interstates including I-78.^[64][65] Safety improvements in the 2020s include pavement preservation and widening projects in Pennsylvania, such as work along segments in Lehigh and Northampton counties to improve shoulders and reduce runoff-road incidents.^[38] Additionally, truck inspection stations at rest areas along I-78, such as the Bloomsbury weigh station, enforce weight and safety compliance to curb oversized vehicle accidents.^[66] Following the completion of I-78 in 1991, traffic on parallel U.S. Route 22 decreased, with accidents dropping from 360 in 1989 to 314 in 1990, and zero fatalities on the new I-78 in its first year, attributed to the controlled-access design eliminating at-grade intersections and improving traffic flow.^[67]

Economic and environmental effects

Economic contributions

Interstate 78 has significantly contributed to job creation in the Lehigh Valley region of Pennsylvania, generating thousands of direct employment opportunities in logistics, manufacturing, and distribution since its completion in the early 1990s. A 1993 report by the Lehigh Valley Planning Commission documented a net increase of approximately 1,800 jobs in Lehigh County and 1,400 in Northampton County between 1989 and 1992, attributing this growth to I-78's role in helping the area weather the early 1990s recession by attracting industrial development.^[68] More recent expansions, particularly in warehousing, have amplified this impact; for instance, Amazon's facilities in the Allentown area, accessible via I-78, employ approximately 3,400 workers as part of the company's broader Pennsylvania investment exceeding $6 billion since 2011.^[69] These hubs, including major operations for e-commerce fulfillment, underscore I-78's support for high-wage logistics roles, with the Lehigh Valley adding 9,080 jobs across sectors in the five years leading up to 2024, including growth in manufacturing and distribution.^[70] The Lehigh Valley's GDP reached a record $55.7 billion in 2023. The highway facilitates substantial freight movement, enhancing trade efficiency across Pennsylvania and New Jersey. Annually, more than $60 billion in goods traverse the Lehigh Valley via I-78, supporting regional supply chains and reducing shipping times compared to pre-interstate routes like U.S. Route 22.^[71] A 1993 study highlighted I-78's early benefits, noting improved safety on Route 22—where fatal accidents dropped from six in the two years prior to its opening to two in the two years after—alongside spurred industrial development due to diverted truck traffic and easier access for shippers.^[68] In New Jersey, the eastern segment of I-78 provides critical connectivity to Port Newark-Elizabeth, the East Coast's busiest container port, which handles over $211 billion in annual international freight and bolsters the regional economy through enhanced goods distribution.^[72] Post-2020, the e-commerce boom has intensified I-78's economic role, driving increased truck traffic and GDP contributions amid surging online retail demand. Daily truck volumes on I-78 in the Lehigh Valley rose from about 7,000 in 1999 to over 22,000 by 2025, fueled by warehouse expansions that added 7.2 million square feet of logistics space under construction by late 2020.^[73] This growth supported a 6% rise in distribution sector employment to 32,279 jobs in mid-2020 and contributed to the Lehigh Valley's record $43.3 billion GDP in 2019, with logistics adding an estimated $2 billion in regional value through heightened freight activity during the pandemic recovery.^[74]

Environmental considerations

The construction of Interstate 78 encountered substantial environmental opposition, particularly in New Jersey, where plans to route the highway through the Watchung Reservation—a 2,000-acre protected area—drew protests from conservation groups and residents concerned about habitat loss, deforestation, and fragmentation of parklands.^[75] In response to this pressure, the route was adjusted to the reservation's northern edge, minimizing direct intrusion while incorporating mitigation features such as two pioneering wildlife overpasses built in the mid-1980s; these structures, primarily benefiting deer and other mammals, have effectively reduced wildlife-vehicle collisions and preserved ecological connectivity.^[76] In Pennsylvania, the Allentown-Bethlehem-Easton bypass segment faced legal challenges under Section 4(f) of the U.S. Department of Transportation Act of 1966, a new federal provision safeguarding public parklands from incompatible transportation projects; environmental activists' lawsuit tested this law, delaying construction for over a decade and requiring comprehensive environmental impact studies that assessed alternatives and mitigation strategies.^[77] These studies led to design modifications, including restrictions to six lanes in Lehigh County and four lanes in Northampton County, to lessen ecological disruption in sensitive areas like the Lehigh Valley.^[7] Across New Jersey portions, I-78's development and maintenance have affected freshwater wetlands, with projects such as the I-287/I-78 interchange improvements authorizing temporary impacts to 0.050 acres of wetlands and 4.479 acres of transition areas, offset by required mitigation including wetland restoration and creation elsewhere.^[78] Noise pollution from the highway, especially near parks like the Watchung Reservation and Hidden Valley, prompted targeted studies identifying 10 mitigation sites where barriers were installed to protect adjacent habitats and communities.^[79] Ongoing operations contribute to air quality challenges in urban corridors, with vehicle emissions exacerbating regional smog and greenhouse gas levels in the New York metropolitan area. Recent widening proposals for the I-78 extension along the New Jersey Turnpike have intensified scrutiny, as environmental advocates demand a full Environmental Impact Statement to evaluate cumulative effects on wetlands, air quality, and environmental justice communities disproportionately burdened by pollution and construction noise.^[80]