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roundabout

Roundabout and Innovative Intersection/ Interchange Support

Urban is providing peer review and design assistance services for innovative infrastructure under an open-end agreement with PennDOT’s Bureau of Project Delivery, which is part of their Central Office.  

Details
Markets
Services Provided
Site and Land Development
Client
PennDOT
Project Contact
Michael Mastaglio, PE, PTOE
215.922.8080

PennDOT Central Office - Roundabout and Innovative Intersection/Interchange Support

Responding to the State Transportation Innovation Council — a concept introduced by the Federal Highway Administration in 2010 — PennDOT is increasing its use of new transportation design techniques, such as innovative interchanges and intersections, to improve transportation safety statewide.

 

With this push towards innovation, PennDOT has engaged experts from the consultant community, such as Urban, to assist with design. We are providing peer review and design assistance services for innovative infrastructure under an open-end agreement with PennDOT’s Bureau of Project Delivery, which is part of their Central Office. Services include policy development, education, and training; identification, planning, and design of roundabouts and innovative interchanges/intersections; and peer review.

 

roundabout rightsizing

“Right-Sizing” is the first step in Urban’s roundabout peer review process. We try to determine whether the roundabout can support traffic projected over the next 20 years.

roundabout capacity

VISSIM simulation helps clients and the public understand how traffic on the roundabout might look in the future.

roundabout geometry review

Sample review of consultant designs.

roundabout ddi geometry review

Sample review of a consultant’s Diverging Diamond Interchange design. Use of this innovative design is expected to increase in the future.

sr 209 recommended geometry revisions

Urban's recommended geometry improvements and design vehicle checks of a roundabout peer review

We focus on safety, traffic operations, and geometric design improvements when reviewing or designing alternative intersections and other innovative infrastructure. Techniques which PennDOT is investigating include the following: 

  • Roundabouts and roundabout corridors
  • Diverging diamond interchanges (DDI)
  • Displaced left-turn intersections
  • Single-point urban interchanges (SPUI)
  • Restricted crossing U-turn intersections
  • U-turn intersections
  • Superstreets
  • Median U-turns, J-turns
  • Continuous flow intersections (CFI)

 

Highlights

  • Identified ten candidate sites and three candidate corridors for roundabouts based on analysis of safety, access, delays, and impacts to the Transportation Improvement Plan (TIP) implementation
  • Drafted PennDOT’s Roundabout Policy, Design Manual 2
  • Performed the first pilot countywide roundabout study for PennDOT District 8-0, in Lancaster County, and continued to refine these studies for Berks, Lehigh and Northampton Counties in PennDOT District 5-0
  • Developed fishhook pavement marking standards
  • Provided input on changes to Design Manual-2 and Design Manual -1A to reflect NCHRP 672 updates and current best practices
  • Developed a user guide for SIDRA, a widely-used software tool in the USA for roundabout capacity and performance analysis
  • Updated RC standards to incorporate roundabout guidance
  • Staff of national roundabout and alternative intersection policy experts