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New Detour Begins Monday for Route 320 (South Gulph Road) Improvement Project at Hanging Rock in Upper Merion Township


King of Prussia, PA – Route 320 (South Gulph Road) motorists will be directed to use a new detour route beginning Monday morning, June 14, under a project to improve travel and safety by shifting the roadway alignment away from the historic Hanging Rock between Upper Gulph Road and Arden Road in Upper Merion Township, Montgomery County, the Pennsylvania Department of Transportation (PennDOT) announced today. The entire project is expected to finish this fall.

Beginning Monday, June 14, through November, Route 320 (South Gulph Road) motorists will be directed to use the following detours:

  • Northbound Route 320 (South Gulph Road): Matsonford Road, westbound Interstate 76, exit at the Route 320/Gulph Mills Interchange and turn left on Balligomingo Road to access Route 320 (Trinity Lane/South Gulph Road); and
  • Southbound Route 320 (South Gulph Road): Eastbound I-76, exit at the Conshohocken Interchange, turn left on Matsonford Road and right on Old Gulph Road to access Route 320 (South Gulph Road).

Drivers are advised to allow extra time when traveling near the work area because backups and delays will occur.

The current detour has drivers using I-76, Interstate 476, U.S. 30 (Lancaster Avenue), Spring Mill Road and Old Gulph Road because of a nearby PECO utility improvement project on Matsonford Road between Montgomery Avenue and Hillside Avenue that began on March 31. PECO will complete the gas main improvement project about six weeks early and is expected to reopen Matsonford Road by Monday morning, June 14.

Under the improvement project on Route 320 (South Gulph Road), PennDOT’s contractor will:

  • Reconstruct the cantilevered structure that carries Route 320 (South Gulph Road) over Gulph Creek;
  • Raise the profile of Route 320 (South Gulph Road) to meet the requirements for the 100-year flood elevation;
  • Improve the Route 320 (South Gulph Road) and Upper Gulph Road Intersection by adding a southbound right-turn lane on Route 320 (South Gulph Road);
  • Perform drainage improvements; and
  • Install ADA curb ramps and traffic signal upgrades.

Work on this project will be in accordance with Centers for Disease Control and state Department of Health guidance as well as a project-specific COVID-19 safety plan, which will include protocols for social distancing, use of face coverings, personal and job-site cleaning protocols, management of entries to the jobsite, special signing, and relevant training.

Allan Myers, LP, is the general contractor on the $8,180,888 project which is financed with 100 percent state funds.

Motorists can check conditions on more than 40,000 roadway miles by visiting 511PA, which is free and available 24 hours a day, provides traffic delay warnings, weather forecasts, traffic speed information and access to more than 1,000 traffic cameras.

For a complete list of construction projects impacting state-owned highways in Bucks, Chester, Delaware, Montgomery and Philadelphia counties, visit

Information about infrastructure in District 6 including completed work and significant projects, is available at Find PennDOT’s planned and active construction projects at

Follow PennDOT on Twitter at and like the department on Facebook at and Instagram at

MEDIA CONTACT: Brad Rudolph, 610-205-6800

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 RT 320 South Gulph Rd Closure and Detour.jpg