BACKGROUND

Alternative intersection and interchange (A.I.I.) designs initially emerged as a way to improve safety and operations while reducing project costs and impacts, with the potential to enhance facilities for pedestrians and bicyclists.

Early consideration and implementation by agencies were supported by the Federal Highway Administration (FHWA) Alternative Intersections/Interchanges Informational Report and a series of informational guides published since 2014. More recently, the North Carolina Department of Transportation (DOT) released an annotated outline for an updated informational report, and FHWA published a new guide focused on pedestrian and bicyclist safety at alternative intersections. Additionally, recent NCHRP reports provide detailed guidance on roundabouts, multimodal safety at alternative intersections, and intersection control evaluation.

Research is needed to develop a guide on several widely adopted intersection types, reflecting the growing knowledge and experience from successful implementations by many DOTs. The guide also will focus on expanding the toolbox of A.I.I. types and options to help DOTs enhance multimodal transportation safety and operational efficiency.

OBJECTIVE

The objective of this research is to develop a guide to support state DOTs and other transportation agencies in considering A.I.I.s in their project planning and development process. The guide will consist of two parts:

• Part I will provide comprehensive information on U-turn-based intersections, covering key issues related to planning, implementation, operation, and maintenance; and
• Part II will provide an expanded resource on A.I.I.s, focusing on the efficacy of underutilized, emerging, or new concepts, as well as their variations.

To achieve the research objective, the research team shall, at a minimum, consider the following key elements:

• Identification and evaluation of existing and emerging alternative design concepts and treatments in the United States and internationally;
• Review of research and practices that complement the objectives and address gaps in previous guides;
• Development of criteria for applying appropriate treatments and design features based on context (e.g., traffic data, land use and access, expected users, roadway data, speed, flexibility);
• Consideration of all modes of transportation and users of all ages and abilities;
• Preparation of standardized definitions of terms; and
• Harmonization with applicable standards and guidelines.

RESEARCH PLAN

To achieve the objective of this research, at minimum, the proposed tasks should include:

• Initial Research and Analysis:
  • Review existing literature, resources, and published practices to establish a foundational understanding of A.I.I. designs;
  • Gather and incorporate insights from practitioners to enhance the guide’s relevance and practical applicability;
  • Identify and address specific knowledge gaps;
  • Use a systematic process of vetting and review to select A.I.I. designs for a minimum of 20 emerging and underutilized alternative design concepts, based on the latest knowledge, practices, and lessons learned.
• Guide Development – Part I:
  • Propose a prioritized list of specific research topics to support the guide development;
  • Prepare an annotated description of the proposed guide for NCHRP approval;
  • Carry out the research and develop a comprehensive guide on U-turn-based intersections, covering planning, implementation, operation, and maintenance.
• Guide Development – Part II:
  • Create a template to show the considerations, e.g., analysis, design, operation, evaluation, etc., that will be discussed in each A.I.I. design concept, balancing breadth and depth;
  • Develop an expanded resource on A.I.I.s that includes a high-level overview of A.I.I. design concepts and how to contrast and compare various A.I.I.s, along with approximately two to 10 pages of detailed content for each of the 20 selected alternative design concepts.
• Workshop
  • After NCHRP approval of the draft guide, plan and conduct an in-person workshop to debrief the proposed guide and solicit additional feedback from the selected invitational attendees and NCHRP.  

The research plan should build in appropriate checkpoints with the NCHRP project panel, including at a minimum (1) a kickoff teleconference meeting to be held within 6 weeks of the contract’s execution date, (2) two web-enabled teleconferences interim report review meetings, and (3) web-enabled teleconferences tied to panel review and NCHRP approval of other deliverables.

The final deliverables shall include:

• A guide on alternative intersections and interchanges;
• A conduct of research report with an executive summary that documents the entire research effort;
• A technical memorandum titled “Implementation of Research Findings and Products”; and
• A PowerPoint presentation with speaker notes that summarizes the project and intersection types, clearly illustrating how the research can be applied to a broader audience.

STATUS: Proposals have been received in response to the RFP. The project panel will meet to select a contractor to perform the work.