Our firm was retained by PennDOT for the preliminary engineering and final design of the $3.5M “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. For years, drivers in the area have endured significant congestion and difficult traffic conditions at this intersection, mostly due to the unconventional five-leg configuration.
Our firm 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 team conducted two CAC meetings, which included representatives from the local municipalities, Dallas Borough’s Downtown Revitalization Team, 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 us 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 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 was submitted and advertised for construction through PennDOT’s Engineering and Construction Management System (ECMS).