U.S. Department of Transportation
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Motorists, pedestrians, and bicyclists face greater mobility challenges and safety risks at intersections as traffic volumes grow and congestion worsens. Agencies need safer, more balanced designs that keep people moving. Innovative intersection designs offer many safety and operational benefits, and are being built more often because they can deliver more for less. Continuous Green T, Offset T, Quadrant Roadway and Jughandle designs are a few innovative designs in use in a small number of states, and have shown promise in reducing crashes and improving operations.
There are other innovative designs as well – including many that are only schematic concepts at this time. The common characteristic across all types of innovative intersection designs is the reduction in the number and severity of conflict points. The diagram below illustrates the difference in conflict points between a conventional, four-legged intersection, an equivalent Quadrant Roadway design and an equivalent Offset T design. There are 32 conflict points associated with a conventional intersection – 8 merging (or joining), 8 diverging (or separating) and 16 crossing.
Vehicle-Vehicle Conflict Points |
Conventional Intersection |
Quadrant Roadway | Offset T |
---|---|---|---|
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Crossing | 16 | 8 | 6 |
Merging | 8 | 10 | 6 |
Diverging | 8 | 10 | 6 |
Total | 32 | 28 | 18 |
To help explain the concepts and raise awareness about additional innovative geometric designs, the following resources were prepared by FHWA:
Informational Case Studies
Public Roads Magazine Articles
"Design at the Crossroads”, Jul/Aug 2013, Vol. 77, No. 1 [HTML]
National Highway Institute Course #380109 "Alternative Intersections & Interchanges" [HTML] [PDF]
Capacity Analysis for Planning of Junctions (CAP-X) Tool [HTML]
State Highway Agency Resources:
Indiana DOT – Intersection Decision Guide (Indiana, 2014) [PDF]
Iowa DOT/Iowa State University CTRE – Intersection Resources [HTML]
Kentucky Transportation Cabinet/Kentucky Transportation Center
Congestion Toolbox: Continuous Green T Information [HTML]
Intersection Design Analysis Tool (IDAT) [HTML]
Maryland SHA – Applied Technology and Traffic Analysis Program Tools [HTML]
Unconventional Arterial Intersection Design Presentation [HTML] [PPT]
Unconventional Intersection Design Analysis (MUID) Tool [HTML]
New Jersey DOT – Roadway Design Manual [HTML] – Jughandles [HTML]
North Carolina DOT – Quadrant Roadway Video [YouTube] and Brochure [PDF]
Ohio DOT – Quadrant Roadway Video [YouTube]
Texas DOT/Texas Transportation Institute – Mobility Strategies (Texas, 2013) [HTML]
Innovative Intersections – Executive Summary [PDF] – Technical Information [PDF]
Quadrant Roadway Intersections – Technical Information [PDF]
Virginia DOT – Quadrant Roadway Video [YouTube]
Improving Intersection Design Practices (Kentucky, 2011) [PDF]
An Integrated Computer System for Analysis, Selection and Evaluation of Unconventional Intersections (Maryland, 2011) [PDF]
Safety and Operational Impacts of Alternative Intersections (Indiana, 2008) [PDF]
Transportation Research Board Intersections Joint Subcommittee (AHB65(1)) Home Page [HTML]