BACKGROUND

The American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual (HSM) has crash prediction methods for multilane roadway facilities, but only a few of the available methods address the safety performance of these facilities with long-duration work zones (defined as work zones with temporary traffic control [TTC] devices that remain in place for extended time periods [i.e., multiple weeks or months]) in place. As a result, state departments of transportation (DOTs) and other highway agencies rely on judgment and experience rather than quantitative safety analysis in developing TTC plans for long-duration work zones.

Research is needed to better understand the quantitative safety performance, including crash frequency and crash severity measures, of a variety of work zone TTC characteristics. These characteristics include speed limit, lane closures, lane shifts, shoulder closures, median crossovers, lane width, shoulder width, horizontal curvature, offsets from the traveled way to traffic barriers, breakdown bay (i.e., emergency pull-off area), and construction access points. New knowledge on these topics should be assembled into quantitative crash prediction methods that can be used by state DOTs and other highway agencies in developing TTC plans. 

OBJECTIVE

The objective of this project is to develop crash prediction methods and supporting spreadsheet tools for state DOTs and other highway agencies to plan and design TTC for long-duration work zones on high-speed (45 mph or higher) multilane roadway facilities. 

The crash prediction methods should be capable of comparing the expected safety performance of different work zone design options to assist in planning work zone configurations and project phasing. These crash prediction methods should have a similar structure to existing HSM crash prediction methods, with safety performance functions and crash modification factors. The research may adapt these approaches as needed to provide an effective procedure and structure for the models to provide crash frequency and severity estimates. These crash prediction methods should be suitable for incorporation in future editions of the AASHTO HSM. 

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

RESEARCH PLAN

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. The work proposed must be divided into tasks and/or phases. Proposers must describe the work proposed in each phase and task in detail.

The research plan should build in appropriate checkpoints with the NCHRP project panel, including, at a minimum, (1) a kick-off teleconference meeting to be held within 1 month of the contract’s execution date and (2) one face-to-face interim deliverable review meeting and web-enabled teleconferences tied to panel review and/or NCHRP approval of the interim deliverables, including the expenses in the budget. The cost of teleconferences, the in-person meeting venue, and NCHRP panel member travel will be paid by the NCHRP.

At a minimum, the proposed tasks should be accomplished.

Phase I

Task 1. Conduct a critical review of the road safety literature and a survey of the state of the practice at state and other agencies to identify factors associated with the performance of work zone TTC characteristics. The review should summarize the factors considered, discuss related modeling efforts, and identify gaps in the current state of knowledge and practice on the research topic.

Task 2. Identify data currently used and other public data that could help develop exposure and crash prediction models for use in long-duration work zones. Develop a comprehensive data collection, management, and validation plan. The plan should include metadata for raw and processed data, data ownership information, data restrictions (if applicable), and recommendations for data archiving.

Task 3. Prepare a detailed methodological framework for developing crash prediction models. Examine key factors for evaluating the performance of long-duration work zone TTC characteristics.

For the crash prediction modeling task, the methodological framework shall, at a minimum, include:

• Methods for multisource data integration/fusion;
• A 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;
• A validation approach for the methodology and tool; and
• Development of a spreadsheet tool.

The methods for the prediction of crash frequency and severity for long-duration work zones should be repeatable, capable of evaluating existing and future conditions, and practical and readily implementable by state and other transportation agencies of all sizes to help evaluate the potential performance of a long-duration work zone at a given location.

NOTE. Model development and validation requires the selection of independent variables, functional form, model methods, and so forth. Consistent with reproducibility best practices, the researchers should provide documentation and justification for variable selection and functional forms in each model beyond the simple use of p-values. This includes documentation of preliminary and intermediate model testing variables not included in the final models. Examples of selection criteria and methods that should be considered and documented include, at a minimum, improved predictive power in model validation for predictive models, such as accuracy and variance; elasticities, marginal effects, or other interpretive measures for the sign and magnitude of estimated coefficients; considerations of both omitted and included variables bias; and costs and difficulties in collecting and maintaining data elements for transportation agencies and practicing engineers. For model validation, the best methods for validation should consider the purpose of the models being developed, sample size, and so forth and select the most appropriate methods.

Task 4. Prepare an interim report documenting the results of Tasks 1 through 3 and provide a work plan for Phase II no later than 8 months after the contract is awarded. 

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. Phase I budget shall not exceed $100,000.

Phase II

Task 5. Execute the work plan based on the approved interim report. Prepare a technical memo with the research findings.

The Task 5 technical memo shall include detailed discussions on the impact of the significant variables, including sign of impact (i.e., positive or negative), magnitude, and elasticities (or marginal effects), with the purpose of improving the scientific understanding of the performance of long-duration work zone TTC characteristics. The documentation for model development should include:

• Detailed methodology;
• Data summary and descriptive statistics by facility type and work zone with TTC characteristics;
• Validated models and results, including variable importance ranking, and elasticities (or marginal effects) of analyses by facility type and work zone with TTC characteristics;
• Metrics used for assessing the quality of statistical models and results of the quantitative analyses; and
• Tables and graphs showing relationships between crash frequency/severity and key independent variables.

Provide all assumptions, data limitations, and other constraints (e.g., range for valid input fields, conditions that cannot be assessed with the methodologies because the data sources used to develop the method did not include these conditions).

Task 6. Develop a user-friendly, updatable, and easy-to-maintain spreadsheet tool and user manual with example applications that can be used by practitioners of state and other transportation agencies to quantify the performance of long-duration work zones. The development of the spreadsheet tool should use commonly available software and avoid the use of third-party software components.

Task 7. Refine and update the spreadsheet tool and user manual based on comments from the NCHRP. 

Task 8. Prepare draft language for consideration by AASHTO to incorporate the research results into the next update of the AASHTO HSM (herein called the AASHTO Deliverable). Include sample problems, assumptions, data limitations, and other constraints (e.g., range for valid input fields, conditions that cannot be assessed with the methodologies).

Task 9. Present the research findings in-person or virtually to appropriate AASHTO technical committees for comments and propose any revisions to the NCHRP. The research team should anticipate making at least two presentations during the research process to appropriate technical committees at the meetings of the AASHTO Committees on Safety, Construction, Traffic Engineering, Design, or other technical committees with the NCHRP’s approval. Revise the AASHTO Deliverable after consideration of the review comments and NCHRP approval.   

Task 10. Prepare the final deliverables, including:

1. A final research report documenting the entire research effort; 
2. The AASHTO Deliverable;
3. All raw, cleaned, and processed data collected and used in the research (data should be provided in as close to its raw form as possible based on contractual or legal restrictions), input data sets, fused and integrated research data sets, data dictionaries, data models, and so forth;
4. The spreadsheet tool (including annotated spreadsheet macro code, if any), user manual, and any other spreadsheet tool documentation;
5. Media and communication material [e.g., presentations, two-page executive-level flyer, graphics, graphic interchange formats, press releases]; and
6. A stand-alone technical memorandum titled “Implementation of Research Findings and Products” (see Special Note J for additional information).

Note: The research plan may include additional deliverables and additional panel meetings via teleconference. 

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 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.

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/7083. 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. 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.

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.

M. 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.