BACKGROUND

Advances in the automobile industry, along with the introduction of automated vehicles, have changed vehicle dynamics when navigating curves, particularly in superelevation transitions and fully superelevated sections. Side friction factors based on older vehicle models may no longer align with modern vehicles, vehicle dynamics technologies such as electronic stability control, tire technologies, and pavement surface courses.

Given the advancements in the vehicle fleet, alternative design models should be evaluated for their ability to account for factors such as grade and acceleration/deceleration. Research is needed to update superelevation design criteria based on the impact of these advancements to ensure that horizontal curve designs meet or exceed the safety and performance standards required by modern vehicles and roads.

OBJECTIVE

The objective of this research is to develop performance-based superelevation design criteria. The criteria shall be based on the interaction between vehicles and horizontal curves, performance measures related to safety and user comfort, and acceptable design and construction tolerances.

Accomplishment of the project objective will require at least the following tasks.

TASKS

Task descriptions are intended to provide a framework for conducting the research. The NCHRP is seeking the insights of proposers on how best to achieve the research objective. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must present the proposers' current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objective.

PHASE I – Planning

Task 1. Conduct a literature review of research on vehicle fleet composition, vehicle performance, advanced vehicle technologies, the percentage of vehicles equipped with advanced technologies (e.g., electronic stability control and other performance/safety innovations), tire-pavement friction based on current tire technology and typical pavement surface courses, and alternative design models beyond the point-mass model. The review shall include domestic and international research, databases, and past surveys from published and unpublished sources, as well as contacts with public and private organizations and original equipment manufacturer (OEM) vehicle providers.

Task 2. Evaluate the current and ongoing research and identify components requiring additional study to accomplish the project objective. This may include changes in:

• tire performance
• pavement materials and surface courses
• tire-pavement performance under wet/dry and varying temperature conditions
• vehicle fleet composition (e.g., size, weight, center of gravity)
• vehicle dynamics technologies (e.g., electronic stability control, suspension)
• vehicle operation (traditional human-driven vehicles, driving automation systems, and mixed-fleet operations)
• performance measures related to safety and user comfort
  
• design and construction tolerances (e.g., determining the appropriate interval for superelevation design)

Task 3. Based on the needs identified in Tasks 1 and 2, propose the research plan to be executed in Phases II and III to achieve the research objective. At a minimum, the research plan shall include:

• a framework to establish the appropriate spectrum of design vehicles
• an engagement plan with the Society of Automative Engineers On-Road Automated Driving Committee, the Infrastructure Needs task force, OEM vehicle providers, and similar stakeholders to understand the characteristics of the vehicles and their technologies
• identification of the superelevation design models (e.g., point-mass model, multibody simulation model, vehicle dynamic model) considering factors such as grade and acceleration/deceleration
• identification of design criteria that may need to be updated (e.g., side friction factor [f], superelevation rate [e], distribution of e and f, superelevation transitions, design speed, curve radius, the minimum radius for the normal crown and the maximum superelevation, the minimum length to maintain the superelevated curve, vertical parabolic adjustment at superelevation transition points)
• data analysis and experimental investigation, such as laboratory testing, simulation, and field validation, to support updating the superelevation design criteria based on performance measures related to safety, user comfort, and acceptable design and construction tolerances
  
• development of draft language for the proposed updates to superelevation design criteria for consideration by the American Association of State Highway and Transportation Officials (AASHTO) for incorporation into a future update of the AASHTO Green Book’s chapter on Elements of Design (herein called the AASHTO Deliverable)

Task 4. Prepare Interim Report No.1, which documents the research performed in Tasks 1 through 3 and provides an updated work plan for the remainder of the research, no later than 4 months after contract award. The updated plan must describe the process and rationale for the work proposed for Phases II and III.

Note: Following a 1-month review of the interim report by the NCHRP, the research team will be required to meet virtually with the NCHRP project panel to discuss the interim report. Work on Phase II of the project will not begin until authorized by the NCHRP. The Phase I budget shall not exceed $50,000.

PHASE II – Execution

Task 5. Execute the work plan based on the approved Interim Report No.1.

Task 6. Prepare and submit a preliminary draft of the AASHTO Deliverable based on the results of this work.

Task 7. Prepare Interim Report No. 2, which documents Tasks 5 and 6 and provides an updated work plan for the remainder of the research, no later than 12 months after approval of Phase I. The updated plan must describe the process and rationale for the work proposed for Phase III.

Note: Following a 1-month review of Interim Report No. 2 by the NCHRP, the research team will be required to meet in person with the NCHRP project panel to discuss the interim report. Work on Phase III of the project will not begin until authorized by the NCHRP.

PHASE III – Final Deliverables

Task 8. Revise the draft AASHTO Deliverable based on approved Interim Report No. 2 for the NCHRP panel’s review.

Task 9. Present the research findings to appropriate AASHTO technical committees to collect comments for potential revisions to the AASHTO Deliverable. Update the AASHTO Deliverable considering comments (see Special Note A).

Task 10. Prepare a stand-alone technical memorandum titled “Implementation of Research Findings and Products” (see Special Note K).

Task 11. Prepare presentation materials, in PowerPoint or other formats, for webinars.

Task 12. Submit the final deliverables, including (1) a final report that documents the entire research effort, (2) the AASHTO Deliverable, (3) the Implementation of Research Findings and Products technical memorandum, and (4) the presentation materials.

Note: Following receipt of the draft final deliverables, the remaining 3 months shall be for NCHRP review and comment and for research agency preparation of the final deliverables.

SPECIAL NOTES

A. The research team should anticipate making two presentations to appropriate technical committees at AASHTO meetings.

B. The Information and Instructions for Preparing Proposals for the Transportation Research Board’s Cooperative Research Programs were revised in May 2024. Please take note of the new and revised text which is highlighted in yellow.

C. Proposals must be submitted as a single PDF file with a maximum file size of 10 MB. The PDF must be formatted for standard 8 ½” X 11” paper, and the entire proposal must not exceed 60 pages (according to the page count displayed in the PDF). Proposals that do not meet these requirements will be rejected. For other requirements, refer to chapter V of the instructions.

D. The Information and Instructions for Preparing Proposals for the Transportation Research Board’s Cooperative Research Programs have been modified to include a revised policy and instructions for disclosing Investigator Conflict of Interest. For more information, refer to chapter IV of the instructions. A detailed definition and examples can be found in the CRP Conflict of Interest Policy for Contractors. The proposer recommended by the project panel will be required to submit an Investigator Conflict of Interest and Disclosure Form as a prerequisite for contract negotiations.

E. Proposals will be rejected if any of the proposed research team members work for organizations represented on the project panel. The panel roster for this project can be found at https://www.mytrb.org/OnlineDirectory/Committee/Details/7074. Proposers may not contact panel members directly; this roster is provided solely for the purpose of avoiding potential conflicts of interest.

F. Proprietary Products - If any proprietary products are to be used or tested in the project, please refer to Item 6 in the Information and Instructions for Preparing Proposals.

G. Proposals are evaluated by the NCHRP staff and project panels consisting of individuals collectively knowledgeable in the problem area. The project panel will recommend their first choice proposal considering the following factors: (1) the proposer's demonstrated understanding of the problem; (2) the merit of the proposed research approach and experiment design; (3) the experience, qualifications, and objectivity of the research team in the same or closely related problem area; (4) the plan for ensuring application of results; (5) how the proposer approaches inclusion and diversity in the composition of their team and research approach, including participation by certified Disadvantaged Business Enterprises; and, if relevant, (6) the adequacy of the facilities. A recommendation by the project panel is not a guarantee of a contract. The National Academy of Sciences (NAS - the contracting authority for the National Academies of Sciences, Engineering, and Medicine) will conduct an internal due diligence review and risk assessment of the panel’s recommended proposal before contract negotiations continue.

Note: The proposer's approach to inclusion and diversity as well as participation by Disadvantaged Business Enterprises should be incorporated in Item 11 of the proposal.

H. Copyrights - All data, written materials, computer software, graphic and photographic images, and other information prepared under the contract and the copyrights therein shall be owned by the National Academy of Sciences. The contractor and subcontractors will be able to publish this material for non-commercial purposes, for internal use, or to further academic research or studies with permission from TRB Cooperative Research Programs. The contractor and subcontractors will not be allowed to sell the project material without prior approval by the National Academy of Sciences. By signing a contract with the National Academy of Sciences, contractors accept legal responsibility for any copyright infringement that may exist in work done for TRB. Contractors are therefore responsible for obtaining all necessary permissions for use of copyrighted material in TRB's Cooperative Research Programs publications. For guidance on TRB's policies on using copyrighted material please consult Section 5.4, "Use of Copyrighted Material," in the Procedural Manual for Contractors.

I. The text of the final deliverable is expected to be publication-ready when it is submitted. It is strongly recommended that the research team include the expertise of a technical editor as early in the project timeline as possible. See Appendix F of the Procedural Manual for Contractors Conducting Research in the Transportation Research Board’s Cooperative Research Program for technical editing standards expected in final deliverables.

J. Proposals should include a task-by-task breakdown of labor hours for each staff member as shown in Figure 4 in the Information and Instructions for Preparing Proposals. Proposals also should include a breakdown of all costs (e.g., wages, indirect costs, travel, materials, and total) for each task using Figures 5 and 6 in the brochure. Please note that TRB Cooperative Research Program subawards (selected proposers are considered subawards to the National Academy of Sciences, the parent organization of TRB) must comply with 2 CFR 200 – Uniform Administrative Requirements, Cost Principles, and Audit Requirements for Federal Awards. These requirements include a provision that proposers without a "federally" Negotiated Indirect Costs Rate Agreement (NICRA) shall be subject to a maximum allowable indirect rate of 10% of Modified Total Direct Costs. Modified Total Direct Costs include all salaries and wages, applicable fringe benefits, materials and supplies, services, travel, and up to the first $25,000 of each lower tier subaward and subcontract. Modified Total Direct Costs exclude equipment, capital expenditures, charges for patient care, rental costs, tuition remission, scholarships and fellowships, participant support costs and the portion of each lower tier subaward and subcontract in excess of $25,000.

K. The required technical memorandum titled “Implementation of Research Findings and Products” should (a) provide recommendations on how to best put the research findings/products into practice; (b) identify possible institutions that might take leadership in applying the research findings/products; (c) identify issues affecting potential implementation of the findings/products and recommend possible actions to address these issues; and (d) recommend methods of identifying and measuring the impacts associated with implementation of the findings/products. Implementation of these recommendations is not part of the research project and, if warranted, details of these actions will be developed and implemented in future efforts.

The research team will be expected to provide input to an implementation team consisting of panel members, AASHTO committee members, the NCHRP Implementation Coordinator, and others in order to meet the goals of NCHRP Active Implementation: Moving Research into Practice, available at http://onlinepubs.trb.org/onlinepubs/nchrp/docs/NCHRP_ActiveImplementation.pdf.

L. If the team proposes a Principal Investigator who is not an employee of the Prime Contractor, or if the Prime Contractor is proposed to conduct less than 50% of the total effort (by time or budget), then section five of the proposal should include: (1) a justification of why this approach is appropriate, and (2) a description of how the Prime Contractor will ensure adequate communication and coordination with their Subcontractors throughout the project.

M. All budget information should be suitable for printing on 8½″ x 11″ paper. If a budget page cannot fit on a single 8½″ x 11″ page, it should be split over multiple pages. Proposers must use the Excel templates provided in the Information and Instructions for Preparing Proposals for the Transportation Research Board’s Cooperative Research Programs.

N. The National Academies have an ethical and legal obligation to provide proper attribution whenever material from other sources is included in its reports, online postings, and other publications and products. TRB will review all Cooperative Research Programs draft final deliverables using the software iThenticate for potential plagiarism. If plagiarized text appears in the draft final deliverable, the research team will be required to make revisions and the opportunity to submit future proposals may be affected.