Interstate 78: Wikis


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Interstate 78 shield
Interstate 78
Main route of the Interstate Highway System
Length: 143.56 mi (231.04 km)
Formed: 1957
West end: I-81 in Union Township, PA
PA 61 in Hamburg

I-476 / Penna. Tpk. near Allentown, PA
I-287 in Bedminster, NJ
Route 24 in Springfield, NJ
G.S. Pkwy. in Union/Hillside, NJ
I-95 / NJ Turnpike in Newark, NJ

East end: Canal Street in New York, NY

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.


Route description



Approaching the Interstate 78 and Interstate 81 interchange in Union Township, Lebanon County, Pennsylvania.

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).[1]

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.[2][3]

At exit 60 (A-B going westbound), PA 309 south leaves for Quakertown.[4] 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.

New Jersey

After the Interstate 78 Toll Bridge, I-78 enters New Jersey as the Phillipsburg-Newark Expressway.[5] 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.[6] 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.

I-78, US 1-9, US 22, and NJ 21 junction.

Exit 13 is only westbound and is another exit for NJ 173. Nearby the exit, going eastbound, the frontage road merges in.[6] 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.[6] 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.

I-78 eastbound at the Newark Bay Bridge.

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.[6] 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.

New York City

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.

I-78 at the Holland Tunnel.

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).[7]

Major intersections

Auxiliary routes

1955 map of I-178 and I-378

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.

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.


  1. ^ Google, Inc. Google Maps – overview map of I-78 in Lebanon, Berks, and Lehigh Counties [map]. Cartography by Tele Atlas. Retrieved on 2007-08-31.
  2. ^ Google, Inc. Google Maps – overview map of I-78 southeast of Allentown [map]. Cartography by Tele Atlas. Retrieved on 2007-08-31.
  3. ^ Google, Inc. Google Maps – overview Satellite Image of I-78 with six lanes [map]. Cartography by Tele Atlas. Retrieved on 2007-08-31.
  4. ^ Google, Inc. Google Maps – Interstate 78 in Pennsylvania [map]. Cartography by Tele Atlas. Retrieved on 2007-08-31.
  5. ^ New Jersey Department of Transportation. "Interstate 78 straight line diagram". Retrieved 2007-08-31. 
  6. ^ a b c d Google, Inc. Google Maps – I-78, New Jersey, United States [map]. Cartography by Tele Atlas. Retrieved on 2007-08-31.
  7. ^ NYSDOT - Traffic Count Information
Main Interstate Highways (major interstates highlighted)
4 5 8 10 12 15 16 17 19 20 22 24 25 26 27 29 30
35 37 39 40 43 44 45 49 55 57 59 64 65 66 68 69
70 71 72 73 74 75 76 (W) 76 (E) 77 78 79 80 81 82
83 84 (W) 84 (E) 85 86 (W) 86 (E) 87 88 (W) 88 (E) 89 90
91 93 94 95 96 97 99 (238) H-1 H-2 H-3
Unsigned  A-1 A-2 A-3 A-4 PRI-1 PRI-2 PRI-3
Lists  Primary  Main - Intrastate - Suffixed - Future - Gaps
Auxiliary  Main - Future - Unsigned
Other  Standards - Business - Bypassed

Simple English

Interstate 78 is an Interstate Highway in the United States. It goes from Union Township, Lebanon County, Pennsylvania east to New York City. The route is 143.56 miles (231.04 km) long.[1]


Main Interstates (numbers that end in 0 or 5 are colored pink)
4 5 8 10 12 15 16 17 19 20 22 24 25 26 27 29 30
35 37 39 40 43 44 45 49 55 57 59 64 65 66 68 69
70 71 72 73 74 75 76 (W) 76 (E) 77 78 79 80 81 82
83 84 (W) 84 (E) 85 86 (W) 86 (E) 87 88 (W) 88 (E) 89 90
91 93 94 95 96 97 99 (238) H-1 H-2 H-3
Unsigned  A-1 A-2 A-3 A-4 PRI-1 PRI-2 PRI-3


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