Interstate 78

Interstate 78
Route information
Length	143.56 mi (231.04 km)
Existed	1957–present
NHS	Entire route
Major junctions
West end	I-81 in Union Township, PA
Major intersections	PA 61 in Hamburg I-476 / Penna Turnpike near Allentown, PA I-287 in Bedminster, NJ Route 24 in Springfield, NJ G.S. Parkway in Union/Hillside, NJ I-95 / N.J. Turnpike in Newark, NJ
East end	Canal Street in New York, NY
Location
Country	United States
Highway system
Interstate Highway System Main Auxiliary Suffixed Business Future

Interstate 78 (abbreviated I-78) is an Interstate Highway in the Northeast United States, running 144 miles (231 km) from Interstate 81 northeast of Harrisburg, Pennsylvania, through Allentown, Pennsylvania, and western and northern New Jersey to the Holland Tunnel and downtown New York City.

I-78 is not up to modern Interstate standards, and has gotten numerous complaints from motorists on its conditions.^[1]

I-78 begins at a directional-T interchange with Interstate 81 in Union Township, Lebanon County, Pennsylvania, about 25 miles (40 km) northeast of Harrisburg. Near the east end of the county, at exit 8, U.S. Route 22 merges with I-78, running concurrently for the next 43 miles (69 km).^[2]

At exit 51, in Upper Macungie Township, US 22 leaves the highway. Passengers traveling on I-78 eastbound must use this exit to access I-476 (Northeast Extension of the Pennsylvania Turnpike) and westbound travelers must use exit 53. From exits 53 to 60, I-78 runs concurrently with Pennsylvania Route 309. The six lane overlap bypasses the City of Allentown to the south and crosses South Mountain.^[3][4]

At exit 60 (A-B going westbound), PA 309 south leaves for Quakertown.^[5] Six miles later, there is an interchange between Pennsylvania Route 412 and I-78 in Hellertown. Highway 412 also goes to Bethlehem and Lehigh University. At mile marker 71, Pennsylvania Route 33 intersects at Exit 71. Route 33 traverses the Pocono Mountains and goes to Bangor and Interstate 80. The final exit on Interstate 78 in Pennsylvania is for Morgan Hill Road, which goes to Pennsylvania Route 611 and Easton. Interstate 78 then crosses the Interstate 78 Toll Bridge and enters New Jersey.

After the Interstate 78 Toll Bridge, I-78 enters New Jersey as the Phillipsburg-Newark Expressway.^[6] The road begins by running parallel with County Route 642 in the town of Alpha. At 3.94 miles (6.34 km), Exit 3, a partial cloverleaf interchange brings together U.S. Route 22, New Jersey Route 122 and New Jersey Route 173 with Interstate 78 in Phillipsburg.^[7] U.S. Route 22 now runs concurrently with I-78 for the next 15 miles (24 km). Going westbound, exit 4 leaves to the right for County Route 637 and Warren Glen. The next exit, Exit 6, is for County Route 632 in Bloomsbury. However the route number is not signed on Interstate 78. Exit 7 is the first of several eastbound exits for NJ 173. This one is located in Bloomsbury as 173 begins to parallel the interstate. Four miles later, Exit 11 leaves to the right as another Exit for NJ 173. Warren County 614 also is located off the exit. Exit 12, westbound is for NJ 173 again. However, Exit 12 eastbound is for a frontage road parallelling Interstate 78.

Exit 13 is only westbound and is another exit for NJ 173. Nearby the exit, going eastbound, the frontage road merges in.^[7] Exit 15 is for NJ 173 and County Route 513 in Franklin Township. Exit 17 is for NJ 31 in Clinton. In the town of Annandale, US 22 leaves Interstate 78 at exit 18. Route 22 continues towards Bound Brook and Union County. At exit 20, Hunterdon CR 639 intersects. Hunterdon 639 heads towards the Round Valley Recreational Area. Exit 24 is for County Route 523 towards Oldwick. At exit 29, Interstate 287, U.S. Route 202 and U.S. Route 206 interchange with I-78 in Bedminster. At this point, in Somerset County, Exits 33, 36 and 40 are for county routes in Warren Township. At exit 41, I-78 enters Union County.^[7] At exit 45, County Route 527 intersects after parallelling for some time. West of exit 48, I-78 splits into express and local highways. Exit 48 is for New Jersey Route 24 in Springfield. Exit 49A is for one of route 24's spur routes, New Jersey Route 124. Going westbound, Exit 52 is for the Garden State Parkway in Irvington. At Exits 57 and 58, New Jersey Route 21, U.S. Route 1, U.S. Route 9 and U.S. Route 22 intersect Interstate 78. The exit provides access to Newark Airport.

East of exit 58 at the eastern tip of Newark, I-78 becomes the Newark Bay Extension of the New Jersey Turnpike. Past the first toll plaza, I-78 has an interchange with Interstate 95 (The New Jersey Turnpike) and crosses Newark Bay via the Newark Bay Bridge.^[7] The first exit, 14A, is for New Jersey Route 440 in Bayonne. Liberty State Park and the Liberty Science Center can be reached by taking Exit 14B. Exit 14C is the final numbered exit, providing access to the New Jersey Turnpike. New Jersey Route 139 runs concurrently with I-78 as it approaches the Holland Tunnel and enters New York State.

I-78's length in New York is only 1/2 mile (1 km) - half of the Holland Tunnel and the egress-only roundabout immediately beyond the end of the tunnel. The route was planned to run east and north through New York City to end at Interstate 95 in the Bronx, but sections of the planned route, including the Lower Manhattan Expressway, were cancelled.

In New York City, I-78 continues through the limited access egress-only roundabout known as the Saint John's Rotary. The five separate exits from the Rotary are assigned numbers — exits 1 to 5 - in counterclockwise order. The last one — and the logical continuation east — is Exit 5, Canal Street. Under the original plans, I-78 was to continue across Manhattan as the Lower Manhattan Expressway onto the Williamsburg Bridge, and then beyond I-278 on the never-built Bushwick Expressway through Brooklyn into Queens near the John F. Kennedy Airport. A section of I-78 at the airport was built as the Nassau Expressway, later Interstate 878 and now NY 878, though most of the westbound side was never built. East of the airport, I-78 would have turned north on the Clearview Expressway (built north of Hillside Avenue in Queens and now I-295), run across the Throgs Neck Bridge, and forked into two spurs, ending at Interstate 95 via the Throgs Neck Expressway (now I-695) and the Bruckner Interchange via the Cross Bronx Expressway (now part of I-295).^[8]

• Interstate 81 in Union Township, Pennsylvania
• U.S. Route 22 in Union Township and Upper Macungie Township
• Interstate 476 via U.S. Route 22 near Allentown
• Interstate 287 in Bedminster, New Jersey
• U.S. Route 1-9 in Newark
• Interstate 95 (New Jersey Turnpike) in Newark

All of I-78's auxiliary routes serve New York City; however, none of these routes actually intersects I-78, following the route's truncation at the eastern end of the Holland Tunnel.

• Interstate 278 runs from U.S. Route 1/9 near Elizabeth, New Jersey over the Goethals Bridge, through Staten Island, over the Verrazano Narrows Bridge and through Brooklyn and Queens, and across the Triborough Bridge into the Bronx to end at Interstate 95 at the Bruckner Interchange. Interstate 278 was planned to extend west from Elizabeth to Interstate 78 in Union Township, Union County, New Jersey, and was to intersect I-78 at the east end of the Williamsburg Bridge in Brooklyn. Until 1972, I-278 ran along Interstate 895 and a proposed extension to Interstate 95, while Interstate 278 east of I-895 was I-878.
• Interstate 478 is an unsigned designation for the Brooklyn-Battery Tunnel, a spur from Interstate 278 into lower Manhattan. Plans were made to continue it north along the West Side Highway (Route 9A) to Interstate 78 at the Holland Tunnel, but have been canceled. Older plans would have given it the same purpose — connecting I-78 with I-278 - but along the Manhattan Bridge.
• Interstate 678 runs from I-278 at the Bruckner Interchange south over the Bronx-Whitestone Bridge to John F. Kennedy International Airport. It was to intersect Interstate 78 at its south end. Original plans took I-678 west on the Grand Central Parkway to I-278.
• Interstate 878 is an unsigned designation for part of New York State Route 878, a short east–west freeway on the north edge of Kennedy Airport. It was once planned as part of I-78, and now intersects I-678. The number was assigned in 1989.
• A former Interstate 878 existed from 1959 to 1972 along present I-278 east of Interstate 895. (I-895 was part of I-278.)

In eastern Pennsylvania, Route 378 into downtown Bethlehem was once Interstate 378, but was redesignated as a state route after I-78 was rerouted to a new southerly alignment. An Interstate 178 was initially planned as an extension into downtown Allentown, but was canceled due to local opposition.