Interstate 476 begins at Interstate 95 in urban Chester, Pennsylvania. The commuter freeway extends north along the Mid-County Expressway through the western suburbs of Philadelphia, to I-76 at Conshohocken and the Pennsylvania Turnpike (I-276) at Plymouth Meeting. This stretch of freeway is locally known as the “Blue Route”, a nickname referencing the alignment selected during the planning process for the route. Ramp meters operate along the route as well.
Northward from Interstate 276, I-476 overlays the Northeast Extension of the Pennsylvania Turnpike to Allentown, Wilkes-Barre, Scranton and Interstate 81 at Clarks Summit. The tolled portion of the route serves both commuters in Montgomery County and travelers bound for the Pocono Mountains in northeastern Pennsylvania.
Originally only 21 miles in length, the initial length of the “Blue Route” was fully approved by AASHTO on June 9, 1991 after completion of Interstate 476 between I-95 and Conshohocken. The freeway retained this length for less than five years, as further extension was approved in 1996 north to the vicinity of Scranton. At that time, I-476 became the longest three-digit Interstate highway in the system with approximately 130 miles. The route surpassed the previous longest three-digit Interstate route, I-495 around Boston, Massachusetts. Furthermore, several two-digit Interstate routes, such as I-12 in Louisiana, I-19 in Arizona, and I-97 in Maryland are all shorter than Interstate 476.
A $160 million project by the Pennsylvania Turnpike Commission will improve access between Interstate 81 and I-476 south and north of Scranton and convert the Northeast Extension to all electronic tolling (AET). The work is aimed to divert some of the through traffic away from I-81 in Scranton onto the Northeast Extension between Dupont and Clarks Summit. It was previously anticipated that a contract for design work could be awarded in January 2017, with construction projected to run through 2023.5 A revised preliminary design schedule was posted online on January 23, 2019. It outlined final design work from early 2021 to late 2022 with construction between early 2023 and late 2026.
Local officials advocated expansion of I-81 through the Scranton area in the mid-2000s, but costs were already estimated at $1 billion. The Scranton Beltway project provides a cheaper alternative to widening Interstate 81 from Nanticoke north to Clarks Summit. A subsequent study by PennDOT also concluded that improved accessibility to the Northeast Extension might shift 2,500 vehicles per day (vpd) away from I-81 north and 2,200 (vpd) away from I-81 south, including a potential of 80% or more of truck traffic. 2016 traffic counts on the northernmost section of I-476 top out around 10,000 vpd, while the busiest stretch of I-81 to the east peaks at 70,000 vpd.5
One action indicated within the Scranton Beltway Feasibility Study to both better utilize I-476 and reduce congestion along I-81 would be the renumbering of I-476 as a branch of Interstate 81:
Updating existing and providing additional signage could further enhance the utilization of the connections and I-476. In addition, formalizing the Beltway by providing a dual designation (i.e. I476/I-381) to notify motorists that I-476 provides an alternate route to I-81 could further increase utilization.
The Northeast Extension section of Interstate 476 travels west of former U.S. 611 between Philadelphia and Scranton. U.S. 611 was decommissioned in 1972, with portions of the route renumbered as PA 611 and PA 435. U.S. 309 paralleled the Turnpike north from the Fort Washington Expressway to Quakertown before crossing paths with I-476 at Allentown. Downgraded to a state route in 1968, the historic U.S. highway looped west and north from the Interstate 476 corridor to Hazleton and Wilkes-Barre. U.S. 11 runs along I-81 within the vicinity of I-476 between Wilkes-Barre and Scranton.
The Lehigh Tunnel carries Interstate 476 (Pennsylvania Turnpike Northeast Extension) under Blue Mountain. Opened in 1957, the tunnel consisted originally of just a single bore, with one lane of traffic in each direction. A second bore was added during construction from 1989 to November 1991. The tunnel (and the rest of the Northeast Extension) became a part of Interstate 476 in fall 1996. 12/19/16
Prior to 1964, the Pennsylvania Turnpike mainline and Schuylkill Expressway in Philadelphia were designated as Interstate 80S. As such, the branch routes in the Philadelphia area were proposed as I-280 for the Pennsylvania Turnpike east from Valley Forge (current I-276), I-480 for the Mid-County Expressway (I-476), and I-680 for the loop through South Philadelphia and across the Walt Whitman Bridge (I-676, before I-76 switched places with I-676 along the Vine Street Expressway).
Early plans for a limited access route through the west Philadelphia suburbs called for a toll road. Dubbed the Chester Extension, the Pennsylvania Turnpike branch was projected to run south from Plymouth Meeting to Chester. The Federal Highway Act in 1956 shifted jurisdiction of the corridor away from the PA Turnpike Commission to the Pennsylvania Department of Highways.2
Interstate 476 was originally programmed along the Mid-County Expressway, or “Blue Route” between Interstate 95 and the mainline Pennsylvania Turnpike interchange with the Northeast Extension. The Blue Route was one of three alternatives considered for the expressway (see a map of the routes at PAHighways and on the AARoads Forum). Initial construction of I-476 resulted in the completion of two unused roadways by 1978 in the Broomall and Radnor areas. These roads sat idle for many years due to environmental protests and rising construction costs. The first segment opened to traffic was the section between Interstate 76 at Conshohocken and Chemical Road at Plymouth Meeting in 1979.2
Construction of the remaining Mid-County Expressway, however, would be placed on hold until 1985 due to red tape and community opposition.2 Thus, several compromises were made to the overall design of the highway between Interstate 76 and I-95. Of these, various sections were redesigned to better blend into the natural landscape, with the southernmost portion of highway reduced in lanes from six to four. If it were not for these changes, the highway project may have been scrapped.
The southern terminus interchange with I-95 was constructed in 1975. It was not used by drivers until August 17, 1988,2, when the MacDade Boulevard connector, a three-quarters of a mile segment of freeway linking I-95 with MacDade Boulevard at Woodlyn, opened to traffic. Signs for at the semi-directional T interchange referenced “To MacDade Boulevard” until December 19, 19912, when Interstate 476 was completed between MacDade Boulevard (Exit 1) and I-76 (Exit 16).
The final segment of I-476 opened was the direct connection to the Northeast Extension (PA 9 at the time) and Interstate 276. This short segment of highway includes a large toll plaza and directional cloverleaf interchange at I-276. Replacing a tight trumpet interchange between I-276 and PA 9, construction on the three-level interchange with I-476 commenced in late 1989. It was opened on December 16, 1992.2