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This 2005 photo shows the northbound Pennsylvania Turnpike-Northeast Extension (I-476) at EXIT 31 (PA 63 / Sumneytown Pike) in Lansdale. (Photo by Steve Anderson.)

A TURNPIKE SPUR TO THE POCONOS AND BEYOND: In 1947, the Pennsylvania Turnpike Commission (PTC) proposed a series of extensions beyond the existing 160 miles already opened. Legislation signed that year enabled not only construction of extensions east to Valley Forge and west to the Pennsylvania-Ohio border, but also preliminary planning for additional routes in the turnpike system.

As the 1950's began, the PTC commissioned studies for a 111-mile-long "Northeast Extension" that was to link the mainline east-west Pennsylvania Turnpike with the Lehigh Valley and the Scranton-Wilkes Barre area. Once this link was constructed, a 40-mile-long extension was to have been built to connect to the Pennsylvania-New York border, where a spur of the New York State Thruway was to extend the route to Binghamton and Syracuse. (The PTC eventually dropped the extension north of Scranton toward the second half of the decade as it was incorporated into the toll-free I-81.)

The PTC approved the original 111 miles of the Northeast Extension on March 24, 1954, as part of a $225 million financing plan that also was to finance the Delaware River Extension (I-276) toward the New Jersey Turnpike. Officials broke ground for the Northeast Extension the following day.

BUILDING THE PIKE: It took 20 months to build the initial 37 miles of the extension from the southern terminus in Plymouth Meeting north to the current EXIT 56 (US 22 / Lehigh Valley Thruway). This initial section of the four-lane turnpike opened to traffic on November 23, 1955, but the two intervening interchanges at Lansdale (current EXIT 31 / PA 63) and Quakertown (current EXIT 44 / PA 663) did not open until early December.

On December 28, 1955, the PTC extended the turnpike another ten miles north to a temporary interchange at PA 873 in Slatington (Emerald). The interchange was in use for less than a year and a half while work continued on the nearby Lehigh Tunnel.

TUNNELING THROUGH BLUE MOUNTAIN TOWARD SCRANTON: In anticipation of light traffic counts and to expedite construction, engineers decided to build a two-lane tunnel underneath Blue Mountain approximately 14 miles north of Allentown. Although it was the only two-lane section of the Northeast Extension, it was not without precedent: the PTC used two-lane tunneled sections along the original stretch of turnpike.

The 4,461-foot-long Lehigh Tunnel was opened to traffic on April 1, 1957, along with an additional 49 miles of four-lane highway to Wyoming Valley (current EXIT 115 / PA 315) in Pittston, about halfway between Wilkes-Barre and Scranton. (The PTC closed the temporary Emerald interchange at this time.) The tunnel was not named after Blue Mountain because of the existence of another Blue Mountain Tunnel along the mainline turnpike; it would have been named after PTC Chairman Thomas J. Evans if he had not been convicted of conspiracy to defraud the agency of $19 million.

THE FINISHING TOUCHES: On November 7, 1957, the PTC opened the final 16-mile-long stretch of the $200 million Northeast Extension to US 6-US 11 in Clarks Summit. It marked the end of the last turnpike extension project until the construction of the PTC-owned Beaver Valley Expressway (PA 60) during the early 1990's.

At this northern terminus, the Northeast Extension actually loops back south from a high viaduct toward the US 6-US 11 ramps and the I-81 ramps (which were added in 1962). Dirt embankments at the northern terminus hint at the aborted extension of the Northeast Extension toward New York State.

LEFT: This 1990 photo shows construction underway on the second tube of the Lehigh Tunnel on the Pennsylvania Turnpike-Northeast Extension (I-476). RIGHT: This 1991 photo shows the finishing touches being made to the Lehigh Tunnel. (Photos by Pennsylvania Turnpike Commission.)

THE EXTENSION WAS A SUCCESS, BUT IT TOOK SOME TIME: When it opened, PTC officials expressed confidence that the Northeast Extension would cover its debt service costs more than adequately. However, in the first several years after it opened, the turnpike extension paid only about half of its bond interest costs. The lack of connections to the Interstate highway network also hurt in the turnpike's early years (I-81 in 1962, I-80 in 1966, and I-78 in 1989).

As the Poconos became a more popular weekend destination during the 1960's and 1970's, the Northeast Extension gradually became more heavily traveled. By the 1980's, the 22,000 vehicles per day (AADT) that used the tunnel each day - this figure often doubled on busy weekends - strained the capacity of the Lehigh Tunnel.

A NEW PARALLEL TUNNEL: In 1985, the Pennsylvania General Assembly passed Act 61 ("Turnpike Organization, Extension, and Toll Road Conversion Act"), which authorized construction of a second Lehigh Tunnel tube as part of $807 million in bond-financed projects. These projects were to be financed by a series of toll hikes scheduled between 1986 and 1992. In July 1988, the PTC awarded bids for the $37 million Lehigh Tunnel project to two Pennsylvania firms (McCormick, Taylor, and Associates of Philadelphia and GSGSB of Clarks Summit) and one firm from Nova Scotia. Groundbreaking for the tunnel took place on February 14, 1989.

The new tunnel, which was bored 94 feet west of the existing tube, was to be used for southbound traffic, while the existing tube was to be used for northbound traffic. At a length of 4,380 feet, the new tube was 81 feet shorter than the original tunnel. Working around the clock in three shifts, crews holed 3,550 feet through the north side of Blue Mountain and 675 feet through the south side. A one-day strike on December 5, 1989 did little to slow progress on the project.

The parallel Lehigh Tunnel was the first highway project in the United States to use what is known as the "New Austrian Tunnel Method" (NATM) method. Pioneered in Europe during the 1950's, the NATM had been used to build subway systems in Washington and Pittsburgh. Unlike traditional tunnel-building methods that required the installation of steel superstructure following blasting and excavation, the NATM process involved the "shooting" of liquid concrete with a feeder gun (known as "shotcrete") after each rock blasting to stabilize the ceiling and sides. The shotcrete's strength, durability, low permeability, ability to bond with rock, and ease of shaping (the surface could be smoothed while still wet) made it an ideal choice for tunnel engineers.

The new tunnel, whose cost had risen to $45 million during the construction period, opened on November 22, 1991. Both tubes were open to traffic for several days during Thanksgiving weekend until the original tube was closed for a year-long renovation. By Thanksgiving weekend of 1992, the northbound and southbound tubes were open to traffic permanently.

This 2008 photo shows the southbound Pennsylvania Turnpike-Northeast Extension (I-476) where the I-78 overpass crosses the turnpike in Allentown. There is no direct connection between I-476 and I-78 even though the restriction covering direct toll road-to-Interstate connections had been dropped when I-78 was completed in 1989. Even today, all connections are made indirectly through EXIT 56. (Photo by Steve Anderson.)

CHANGES FOR INTERCHANGES: The PTC completed the following interchange projects in the 1990's:

  • EXIT 20 (I-276 / Plymouth Meeting): On December 16, 1992, the PTC completed the three-year, $55 million reconstruction of the Northeast Extension's southern terminus. The rebuilt interchange, which replaced the old "trumpet" interchange connecting I-276 with the old PA 9, provides a transition between the turnpike and the newly completed I-476 (Mid-County Expressway / "Blue Route").

  • EXIT 115 (PA 315 to I-81 / Wyoming Valley): When the PTC rebuilt this interchange in an $11 million project between March 1991 and November 1992, it replaced the ramp tolls with a new mainline toll plaza (which now is northern terminus of the "ticket system") located about two and one-quarter miles south of EXIT 115. However, the interchange kept its original "double-trumpet" design.

  • EXIT 122 (Keyser Avenue / Taylor): Built during 1991 and 1992, the Keyser Avenue interchange - the newest one on the Northeast Extension - provides the only access to I-476 for 16 miles between Wyoming Valley and Clarks Summit. The interchange was the first "diamond" interchange built on the turnpike system and remains one of only two in the system. Tolls are collected at a mainline toll plaza (the "Keyser Avenue Toll Plaza") located about one mile south of EXIT 122.

  • EXIT 131 (I-81 / US 6-US 11 / Clarks Summit): This interchange also was rebuilt during the early 1990's.

PA 9 BECOMES I-476: On November 1, 1996, the Federal Highway Administration (FHWA) approved the PTC's petition to re-designate the Northeast Extension as part of I-476. The PTC had lobbied for many years to get an Interstate designation to raise awareness of the Northeast Extension - it had applied the PA 9 designation on this road during the 1970's - but was unable to do so because of restrictions then in place.

WIDENING PROPOSED IN MONTGOMERY COUNTY: In 1999, the PTC initiated studies on widening I-476 to six lanes (from four) from EXIT 20 (I-276) in Plymouth Meeting north to EXIT 31 (PA 63) in Lansdale. Construction finally began in late 2007 with the replacement of eight bridges over the turnpike and expansion of 12 additional bridges along the turnpike's mainline. When completed, the 11-mile-long stretch will have not only six travel lanes, but also standard 12-foot-wide inner and outer shoulders (there currently is no inner shoulder and only a 10-foot-wide outer shoulder). The $200 million project is scheduled for completion in 2013.

According to the Pennsylvania Department of Transportation (PennDOT), the Northeast Extension carries approximately 45,000 vehicles per day from Plymouth Meeting north to the Lehigh Valley, about 25,000 vehicles per day from the Lehigh Valley north to the Wyoming Valley exit, and about 10,000 vehicles per day through the remainder of the route north to Clarks Summit.

This 2002 photo shows the southbound Pennsylvania Turnpike-Northeast Extension (I-476) approaching EXIT 95 (I-80 and PA 940) in Lake Harmony. (Photo by Douglas Kerr,

SOURCES: "Surveys To Extend Pennsylvania Pike," The New York Times (8/09/1953); "Turnpike Extension Route Chosen," The New York Times (3/25/1954); "Earnings Prospects of New Pike Bright," The New York Times (4/03/1954); "Bridge To Connect Two Pike Systems" by Paul Heffernan, The New York Times (4/04/1954); "Pennsylvania Turnpike Link" by Joseph C. Ingraham, The New York Times (11/20/1955); "Up to the Poconos" by William G. Weart, The New York Times (3/31/1957); "Most Toll Turnpike Bonds Becoming Blue Chips" by Paul Heffernan, The New York Times (8/27/1961); "Pennsylvania Turnpike Tolls May More Than Double by '92," The New York Times (2/16/1986); "New Tunnel May Relieve Bottlenecks," The Philadelphia Inquirer (7/06/1988); "A New Vision for an Old Tunnel: Construction Begins on a Twin for Existing System," The Philadelphia Inquirer (7/16/1989); "Lehigh Tunnel Union Workers Walk Off Job," The Philadelphia Inquirer (12/05/1989); "On Turnpike, Light at End of the Tunnel," The Philadelphia Inquirer (6/14/1990); "With a Blast, Lehigh Tunnel Is Cut Through," The Philadelphia Tunnel (6/17/1990); "Tunnel Puts Poconos in Fast Lane Moving Mountains… Sort Of," The Philadelphia Inquirer (11/23/1991); "Study Urges $710 Million in Traffic Projects for Montgomery County" by Melia Bowie, The Philadelphia Inquirer (1/11/2001); "Turnpike Widening Expected in Future" by Beth Cohen, The Lansdale Reporter (10/10/2004); "Milepost A20-A30 Bridge Replacement & Widening Project," Pennsylvania Turnpike Commission (2008); Pennsylvania Department of Transportation; Portland Cement Association; Chris Blaney; Adam Froehlig; Jeff Kitsko; Len Pundt.

  • I-476 and PA 9 shields by Ralph Herman.
  • Pennsylvania Turnpike shield by James Lin.




  • Pennsylvania Turnpike-Northeast Extension and Mid-County Expressway ("Blue Route") exit list by Jeff Kitsko.


  • Pennsylvania Turnpike-Northeast Extension (I-476)

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