Understanding the speed-crash relationship has long been of interest in roadway safety analysis. But the relationship cannot be adequately established without taking into account the many factors that influence both speed and crashes: roadway geometry and context, weather conditions, human factors, vehicle type distribution, and the dynamics of the vehicle and tire.
While a significant amount of research has been conducted to identify relationships between roadway design elements and crashes, research that has also considered the contribution of operating speeds or posted speed is limited. A general subjective understanding of the contribution of operating speed of a highway or freeway, through the dynamics of the vehicle, on the severity of a crash is known: higher speeds are associated with more severe crashes. What is desired is a quantitative understanding of how speed (operating and posted) in conjunction with roadway geometry relates to the likelihood of a crash and to crash severity.
This research would build on existing research to explore the relationships between roadway geometrics, speed (operating and posted), and crashes on high-speed rural highways. These relationships will help inform future design guidelines, posted speed practices, and potential safety countermeasures, which are related to desired outcomes for multiple American Association of State Highway and Transportation Officials (AASHTO) committees, such as design, traffic engineering, and safety.
The objective of this research is to explore the relationships between roadway geometrics, operating speed (as defined in FHWA-SA-10-001), posted speed, and crashes on high-speed rural highways.
At a minimum, the research team shall:
- Identify the relationships between speed (operating and posted), geometric characteristics, and crashes on high-speed rural highways, considering other design elements and road conditions.
- Determine the relative contribution of speed (operating and posted) with various roadway geometric characteristics to crashes (in terms of frequency and severity) for high-speed rural highways.
- Identify and measure the effectiveness of existing mitigation strategies for crashes and speed (operating and posted) on high-speed rural highways.
- Determine if existing crash modification factors (CMFs) for geometric elements can be modified with a speed component, and if speed-related CMFs can be developed that could ultimately be incorporated into the AASHTO Highway Safety Manual (HSM) Part C.
Accomplishment of the project objective will require completion of the following tasks, at a minimum.
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 on previous research about the relationships between roadway geometrics, operating and posted speed, and crashes on high-speed rural highways. The review shall include current practice at state and local agencies; AASHTO; the Institute of Transportation Engineers (ITE) guidelines and standards; safety data from the National Highway Traffic Safety Administration (NHTSA); and published and unpublished research conducted through the NCHRP and the Federal Highway Administration (FHWA) and other national, international, state, and pooled-fund sponsored research.
Task 2a. Propose a stakeholder engagement plan to gather related information, such as undocumented or informal implementation strategies, major concerns, and potential data sources. The stakeholders should include up to 20 representatives from state departments of transportation (DOTs), local agencies, AASHTO groups, TRB committees, etc.
Task 2b. Gather stakeholder inputs based on approved plan from Task 2a.
Task 3. Identify potential data sources, especially with respect to operating speed data and how these data could be analyzed in conjunction with roadway geometric characteristics. Evaluate the quality of the data sources and whether they can support the desired evaluation.
Task 4. Prepare a detailed work plan based on a comprehensive literature review, stakeholder inputs, and analysis of available resource data. The plan should cover the following aspects at a minimum:
- Data collection;
- Method for statistical modeling and data analysis to identify the relationships between roadway geometric characteristics, speed (operating and posted), and crashes (frequency and severity) on high-speed rural roadways, considering other design elements and road conditions;
- Strategies for assessing the effects of study factors (operating and posted speed, roadway geometric characteristics) on crashes and perform sensitivity analysis with respect to inclusion of covariates, model forms, etc; and
- Method to develop improved CMFs or crash modification functions (CMFunctions) for geometric elements, incorporating operating or posted speed.
Task 5. Prepare Interim Report No. 1, documenting the results of Tasks 1 through 4, and provide an updated plan for the remainder of the research no later than 8 months after contract award. The updated plan must describe the method and rationale for the work proposed for Phases II and III.
Note: Following a 1-month review of Interim Report No. 1 by the NCHRP, the research team will be required to meet virtually with the NCHRP project panel to discuss the interim report. Work on Phases II and III of the project will not begin until authorized by the NCHRP. Phase I budget shall not exceed $150,000.
PHASE II – Study
Task 6. Execute the work plan based on approved Interim Report No. 1.
Task 7. Prepare an annotated outline of the draft research report.
Task 8. Prepare Interim Report No. 2 that documents Tasks 6 and 7 and provide an updated work plan for the remainder of the research no later than 15 months after approval of Phase I. The updated plan must describe the process and rationale for the work proposed for Phase III.
Meet with the NCHRP to review the report and obtain approval for subsequent tasks.
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 – Reporting
Task 9. Prepare and submit the draft research report based on approved Interim Report No. 2 for the NCHRP panel’s review.
Task 10. Refine and update the draft research report based on comments from the NCHRP project panel.
Task 11. Present the research findings to appropriate AASHTO technical committees for comment and propose any revisions to the NCHRP. The research team should anticipate making at least two presentations during the research to appropriate technical committees at annual meetings of the AASHTO Committee on Design, Committee on Traffic Engineering, or Committee on Safety. Revise the draft research report after consideration of review comments.
Task 12. Prepare the final deliverables, including:
- A conduct of research that documents the entire research effort and any lessons learned;
- Media and communication material (e.g., presentations, 2-page executive-level flyer, graphics, graphic interchange formats (GIFs), press releases); and
- A stand-alone technical memorandum titled “Implementation of Research Findings and Products.” See Special Note I for additional information. Additional funding may be available for a follow-up contract on the implementation of the results.
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.
A. The Information and Instructions for Preparing Proposals for the Transportation Research Board’s Cooperative Research Programs were revised in May 2022. Please take note of the new and revised text which is highlighted in yellow.
B. 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.
C. 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.
D. 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/6757. Proposers may not contact panel members directly; this roster is provided solely for the purpose of avoiding potential conflicts of interest.
E. 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.
F. 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.
G. 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.
H. 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.
I. 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
J. 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.
K. 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.