As the number and prevalence of intersection types and configurations increase, it has become more challenging for practitioners to quantify the safety effects of constructing these designs. Currently the American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual (HSM) provides safety performance functions for a few conventional intersections based on empirical research, but any deviation from the basic assumptions in the HSM requires the application of one or more crash modification factors (CMFs). Although there are a high number of CMFs from various sources, some apply to alternative intersection forms; fewer apply to complex traditional intersections that diverge from the basic intersections in the HSM. Intersection control evaluation policies and efforts typically promote the consideration of alternative intersections not covered in the HSM, which has limited the ability of practitioners to compare the safety performance of these alternative intersections to conventional designs.
One element that is common to all at-grade intersections is the conflict point, the location where two or more paths may cross. Previous research has demonstrated relationships between the number of conflict points at an intersection and the number of resulting crashes over a given time period. Similarly, crash severity can be roughly correlated to conflict type, angle, and speed. Alternative intersections have been touted as an improvement in safety over conventional forms due to a reduction in total conflict points, conflict point proximity, and speed. There is a need for a new methodology to assess a variety of intersections' safety performance from the perspective of conflict point type.
Note: The following definitions and limits apply to the proposed research. Traffic includes motor vehicles, bicycles, and pedestrians; multimodality does not include transit vehicles or their special lanes. Conflicts are restricted to those between a motor vehicle and either another motor vehicle, a pedestrian, or a bicycle. Intersection conflict points are those conflict points directly associated with intersection operations.
The objectives of this research are to
- Develop a quantifiable method to uniformly identify and describe at-grade intersection conflict point types under different contexts; and
- Develop and validate a predictive methodology, using intersection conflict point types to predict multimodal crash frequency and severity, to supplement those in the HSM Part C models.
Accomplishment of the project objectives 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 objectives. 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 objectives.
PHASE I: Planning
Task 1. Conduct a critical review of the roadway literature on the safety performance of at-grade intersection conflict point types. Submit a technical memorandum that summarizes findings related to conflict point analysis modeling efforts and identifies gaps in the current state of knowledge and practice on the research topic.
Task 2. Based on the findings of Task 1, prepare an assessment of the adequacy of existing data and suggest other data that could help develop traffic exposure and safety prediction methodology based on intersection conflict point types. Develop a comprehensive data collection, management, and validation plan. The plan, which will be conducted in Phase II, should include a data dictionary, metadata for raw and processed data, data ownership information, and recommendations for data archiving. A proposal should avoid data that are not available for public release due to licensing or other restrictions (see Special Note A).
Task 3. Prepare a detailed Phase II work plan that gives a quantifiable method to uniformly describe at-grade intersection conflict point types in different contexts (e.g., speed, multimodal traffic volumes, traffic control, land use, intersection geometry, etc.) and a framework for developing a safety performance prediction methodology using intersection conflict point types based on the findings from Tasks 1 and 2.
For the safety performance prediction methodology development task, the proposed Phase II work plan should include, at a minimum
- A list of intersection conflict point types and characteristics for each (figures to help illustrate the text are encouraged);
- Methods for multisource data integration/fusion;
- Data collection, management, and distribution plan;
- Identified tools or software to be used for data management, processing, and modeling;
- Metrics for assessing statistical models and analysis results;
- Validation approach for the methodology;
- A plan to compare modeling results, using case examples of methodology implementation in different contexts, including at least two types of intersection currently described in the HSM Part C and at least two other types of intersection not included in the HSM Part C; and
- A tool for implementing the methodology.
The methodology for prediction of crash frequency and severity for various facility types should be reliable, capable of evaluating existing and future conditions, practical, and readily implementable by state and local transportation agencies of all sizes to help evaluate potential safety performance at a given location. Using the methodology, practitioners should be able to quantify the safety performance of at-grade intersections based on intersection conflict point types for applications across the range of highway activities, including project level planning, design, operations, and safety management.
Task 4. Prepare Interim Report No. 1 documenting the results of Tasks 1 through 3 and provide an updated plan for the remainder of the research no later than 6 months after contract award. The updated plan must describe the methodology 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 $90,000.
PHASE II: Study
Task 5. Execute the work plan based on approved Interim Report No. 1.
Task 6. Develop a user-friendly, updatable, and easy-to-maintain tool to implement the developed methodology and user manual that can be used and maintained by state and local transportation agencies. The tool development should avoid the use of third-party software components that would not be available for updates and maintenance and should use commonly available or open-source software.
Task 7. Prepare an annotated outline of the draft project report. Include in the documentation for methodology development:
- Data summary and descriptive statistics;
- Detailed description of the methodology, including inputs and outputs;
- Validation method and results, including variable importance ranking and elasticities (or marginal effects) of analyses by intersection conflict point type;
- Performance metrics used for assessing the quality and results of the quantitative analyses; and
- Tables and graphs showing relationships between crash frequency, crash severity, and key independent variables.
Provide all assumptions, data limitations, and other constraints (e.g., range for valid input fields). Explain conditions that cannot be assessed using the methodology.
Task 8. Prepare Interim Report No. 2 that documents Tasks 5 through 7 and provide an updated work plan for the remainder of the research no later than 18 months after approval of Phase I. The updated plan shall 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: Reporting
Task 9. Prepare and submit the initial draft project report, tool and user manual based on approved Interim Report No. 2 for the NCHRP panel's review.
Task 10a. Prepare for workshop(s) with at least 10 representatives from state and local agencies from various geographic regions and of various sizes to review and collect feedback on the draft reports and presentations. Submit workshop materials and proposed attendee list for the NCHRP panel's review and approval.
Task 10b. Conduct one or more workshops as approved in Task 10a. Revise the draft project report, tool, user manual, and other workshop materials taking into account feedback gathered during the workshop and submit for the NCHRP project panel's review.
Note: The costs for the workshop, including invitational travel for at least 10 attendees (not including members of the research team), should be included in the detailed budget for the research. For the purpose of estimating these costs, assume that the workshop will be held at a TRB facility (the Keck Center in Washington, DC, or the Beckman Center in Irvine, CA) or state DOT facilities. The NCHRP will cover costs associated with NCHRP panel member travel. Catering services for all participants, including panel members, should be included in the detailed budget for the research.
Task 11. Update the draft project report, tool, and user manual based on comments from the NCHRP project panel.
Task 12. Prepare draft language for consideration by AASHTO to incorporate the research results in the next update of the AASHTO HSM (hereafter called the AASHTO Deliverable): include sample problems, assumptions, effect sizes, data limitations, and other constraints (e.g., range for valid input fields, conditions that cannot be assessed with the research methodologies).
Task 13. Present the research findings to appropriate AASHTO technical committees for comments and propose any revisions to the NCHRP. The research team should anticipate making two presentations during the research to appropriate technical committees at annual meetings of the AASHTO Committee on Safety or the AASHTO Committee on Design. Revise the draft project report after consideration of review comments received during the meetings.
Task 14. Prepare the final deliverables, including
- The final project report;
- The AASHTO Deliverable;
- All raw and cleaned data collected and used in this research (data should be provided in as close to raw form as possible), input data sets, fused and integrated research data sets, data dictionaries, data models, etc.;
- Documentation of the steps in the data fusion and integration process, including annotated data management code used (if any) to fuse, integrate, and clean the data;
- The tool (including annotated code if any), user manual, and any other tool documentation;
- 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 J 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. To ensure that data produced under this project are accessible, a data archiving and sharing plan shall be prepared by the agency performing the research. Sufficient data should be included to replicate project results. The plan must be submitted with Task 3 and shall include a description of expected activities, schedules, limitations, milestones, and required resources. Researchers should describe briefly the expected schedule for data production and archiving in the CRP permanent repository, the format of the final data set, the documentation to be provided, and whether or not any analytic tools and/or results also will be provided. The plan must include a description of actions planned to ensure quality. Moreover, the plan must specify the resources required to archive and distribute the data expected to be obtained in the course of performing the research. In general, public release of data will not occur before full review and approval by the CRP.
The data archiving and sharing plan must include the following sections:
• Background and significance
• Expected data formats
• Description of data archiving and quality assurance plan
• Description of data sharing plan
• Schedule for data archiving and public release of data
• Milestones for the implementation of the plan
• Resources and budget
B. 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.
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/6733. 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. 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.
J. 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.
K. 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.
L. 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.