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Dallas 5-Leg


PennDOT District 4-0

Dallas Borough





  • Highways, Streets & Structures

  • Traffic & Parking

  • Community Transportation​


  • Topographic survey

  • Traffic data collection & analysis

  • Public involvement (Community Advisory Committee) & public meetings

  • Alignment alternative studies

  • Preliminary engineering

  • Final design (Geometric And Drainage)

  • Utility engineering

  • Erosion & sedimentation control plans

  • Preparation of PS&E Package

  • Post construction stormwater management design

  • Stephen Giampaolo, P.E.


McMahon was the prime consultant responsible for the preliminary engineering and final design of the estimated $3.5 million dollar “Dallas 5‐Leg” intersection improvement project. This project was identified as a “high priority” project in the Back Mountain Area Council of Government’s Transportation Plan, prepared in 2006. The project was completed in 2018, eight months ahead of schedule.

McMahon led a project team, which included subconsultants, PennDOT and a Community Advisory Committee (CAC) in the development of preliminary design alternatives which include conventional intersection configurations and multiple roundabout options. The McMahon Team conducted two CAC meetings, which included representatives from the local municipalities, school district, state representatives, and regulatory agencies to discuss the pros and cons of preliminary design alternatives and to garner input from the stakeholders. After an iterative vetting process, four roundabout options and one conventional intersection alternative were selected for public display at the project’s first public meeting. The public meeting included a presentation of a computer model utilizing VISSIM software of the proposed traffic flow for the alternatives and a video of an existing operating roundabout that was similar to the four roundabout options. The use of VISSIM software enabled McMahon to model not only vehicular traffic operations for the subject roundabout intersection, but also to model pedestrians and transit, with a bus stop immediately west of the roundabout.


The VISSIM model also included key intersections and driveways to local businesses located in the immediate vicinity of the roundabout. The preferred “Oval” roundabout option was presented at the final public meeting. Throughout the public involvement process, our team worked with the Dallas Borough’s planning consultant to coordinate the proposed roundabout design with the Borough’s Downtown Revitalization Master Plan.


The preferred “Oval” roundabout option exhibited many of the characteristics of sustainable design such as no power consumption by the elimination of the traffic signal; less roadway pavement; and lower vehicle energy use and emissions. The roundabout incorporated “Green” infrastructure to meet the current post construction storm water management regulations. The implementation of the “Oval” roundabout resulted in a more pedestrian and bicycle friendly intersection and promotes future retail and office development, meeting the goals of the Borough’s Downtown Revitalization Master Plan.


The project tasks included environmental studies/clearance, utility coordination, preliminary engineering, final design and preparation of construction plans, specifications, and estimate (PS&E package). The project will be submitted and advertised for construction through PennDOT’s Engineering and Construction Management System (ECMS).

Local business have already expressed their happiness with the new roundabout - 

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