The National Academies

NCHRP Synthesis 20-05/Topic 50-11 [Active (Synthesis)]

Alternative Intersection Design and Selection
[ NCHRP 20-05 (Synthesis of Information Related to Highway Practices) ]

  Project Data
Funds: $45,000
Authorization to Begin Work: 5/1/2018 -- estimated
Staff Responsibility: Jo Allen Gause
Research Agency: University of Missouri
Principal Investigator: Henry C. Brown
Effective Date: 10/16/2018
Fiscal Year: 2018

Final Scope

Alternative intersection designs continue to grow as viable options at a variety of area and facility types across the United States. Alternative intersections are created by rerouting one or more movements to remove major conflict points. Agencies use a variety of terms for alternative intersections. Examples include J-turns, continuous flow intersections, median U-turns, and diverging diamond interchanges. By removing conflict points at major intersections, alternative intersections have proved to offer greater safety and operational benefits when compared to conventional intersection design.

The objective of this synthesis is to document the evaluation and selection process within departments of transportation (DOTs) for intersection projects. The synthesis will document the critical factors in making alternative intersection design decisions, including design criteria, illumination requirements, traffic control devices, pedestrian, bike, and truck considerations, and right-of-way requirements. The focus will be on at-grade intersections as well as intersections at interchange ramp terminals. Roundabouts will be included in the assessment of evaluation processes with respect to other alternative intersection options, but the synthesis will not address roundabout specific design criteria.

Information to be gathered includes (but is not limited to);
• Assessment and evaluation tools (e.g., CAP-X, SPICE, state specific tools such as those used by Virginia, Pennsylvania, and Florida);
• Documented DOT intersection evaluation procedures, policies, and guidelines (e.g., ICE, Indiana DOT intersection decision guide);
• Documented design criteria relative to alternative intersections (e.g., Utah DOT DDI guideline and CFI design guidelines, Missouri DOT EPG section on DDIs);
• DOT practices and information resources for public education and outreach (e.g., website, animated drive-through videos;
• Constructability and temporary traffic control;
• Documentation of safety and operation benefits (excluding roundabouts); and
• Barriers to implementation and strategies for overcoming those barriers.

Information will be gathered through literature review, a survey of DOTs, and follow-up interviews with selected agencies for the development of case examples. Knowledge gaps and suggestions for research to address those gaps will be identified.

Information Sources:
• Hatem Abou-Senna, Essam Radwan, Sebastian Tabares, Jiawei Wu, & Sandesh Chalise. “Evaluating Transportation Systems Management & Operations (TSM&O) Benefits to Alternative Intersection Treatments”, Final Report, Florida Department of Transportation Research Center, December 2015.
• Highway Capacity Manual, Transportation Research Board, National Research Council, Washington, D.C., 2016, Sixth Edition.
• Hughes Warren, Ram Jagannathan, Dibu Sengupta, and Joe Hummer. "Alternative Intersections/Interchanges: Informational Report (AIIR)", USDOT, FHWA, Publication No. FHWA-HRT-09-060 April 2010.
• Asokan, Anand, Bared, Joe G, Jagannathan, Ramanujan, Hughes, Warren, Cicu, Federico Illotta, Pier Fabrizio. “Alternative Intersections Selection Tool - AIST.” Transportation Research Board, Presentation at the 89th Annual Meeting of the Transportation Research Board, 10 Jan. 2010.
• Alisa Bowen, Mike Eubank, Jason Kaiser, Dana Plattner, Greg Richards, Bill Smith, Brad Steckler, “Intersection Decision Guide”, Indiana Department of Transportation, January 14, 2014.

TRB Staff
Jo Allen Gause
Phone: 202-334-3826
Email: jagause@nas.edu

Meeting Dates
First Panel:  October 16, 2018, Washington, DC
Teleconference with Consultant: November 8, 2018, 4:00 p.m., EST
Second Panel: June 27, 2019, Washington, DC

Topic Panel
Christina D. Barry, Georgia DOT
Bradford Foley, Maine DOT
Federico Gontaruk, Virginia DOT
John M. Mason, Jr., Penn State Harrisburg
Kenneth L. Mora, Texas DOT
Brad Steckler, Indiana DOT
Mike R. Wahlstedt, TranSystems
Mark Doctor, Federal Highway Administration
Richard A. Cunard, Transportation Research Board

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