BACKGROUND
Roadway departure crashes account for half of all fatalities every year, more than 18,000, with more than 5,000 fatalities resulting from head-on crashes. These crashes occur primarily on undivided, high-speed, rural roads with vehicles traveling in opposite directions, often separated only by a center line pavement marking and possibly a rumble strip. NCHRP Research Report 995: Guidelines for Treatments to Mitigate Opposite Direction Crashes provides guidelines for selecting appropriate safety countermeasures for opposite-direction crashes. The supporting research project, NCHRP Project 17-66, “Guidance for Selection of Appropriate Countermeasures for Opposite Direction Crashes,” found that center line buffer areas reduce opposite-direction crash fatalities significantly and are used around the United States. NCHRP Project 17-66 researchers developed crash modification factors for center line buffer areas of 2 ft, 4 ft, and 6 ft in width.
However, challenges arise during the implementation of center line buffer areas. Transportation agencies must often work within existing roadway pavement areas to implement low-cost safety countermeasures. In cases where the roadway cannot be widened to accommodate the center line buffer area, a practitioner must consider the roadway context and decide between narrowing the lanes or shoulders. Guidelines are needed to inform designers on the overall safety performance of various roadway cross sections with a center line buffer area. The aim is to determine which safety benefit between center line buffer areas and wider lanes and shoulders will guide the decision on where to reallocate pavement area.
Research is needed to develop guidelines and a tool to support the implementation of center line buffer areas so that practitioners can weigh the geometric and operational factors that affect the safety performance of center line buffer areas.
OBJECTIVE
The objective of this project is to develop guidelines and a tool for the implementation of center line buffer areas, with a focus on rural two-lane highways. The project will evaluate the safety benefits of center line buffer areas while considering the reallocation of other cross-sectional elements and develop criteria for implementation.
Accomplishment of the project objective(s) will require at least the following tasks.
TASKS
PHASE I – Planning
Task 1. Conduct a literature review of relevant research, literature, and other sources regarding center line buffer areas related to the project objective. The review shall include published and unpublished research conducted through the NCHRP; the Federal Highway Administration (FHWA); and other national, international, state, and pooled-fund sponsored research.
Task 2. Review state, county, local, federal land management agency, and Tribal policies, practices, and guidelines for implementing center line buffer areas from diverse geographic areas, climates, and contexts within the United States.
Task 3. Conduct a critical analysis and synthesis of the literature and Task 2 results and identify knowledge gaps and opportunities related to the project objective. These gaps must be addressed in the final deliverables if the budget allows or in the recommended future research. Document findings from Tasks 1 through 3 in a technical memorandum.
Task 4. Develop a method to achieve the project objective to be executed in Phases II and III. At a minimum, the method shall formulate strategies to:
- Identify common roadway geometric and operational features that may influence the implementation of center line buffer areas, such as
- Lane and shoulder width,
- Shoulder pavement structure,
- Roadway context,
- Density of access points,
- Average daily traffic,
- Sight distance,
- Roadway users (e.g., trucks, pedestrians, bicycles, etc.),
- Bicycle lanes,
- Right-of-way,
- Roadside conditions (e.g., curb, drainage, clear zone),
- Embankment/cut slopes,
- Posted speed limit (limited to 45 mph speed limit and above),
- Maintenance concerns (e.g., snow removal, work zone traffic control),
- Delineation elements (e.g., rumble strips, flex-posts, pavement markings), and
- Other cross-sectional elements;
- Evaluate the safety and operational trade-offs with various roadway cross-sectional configurations (e.g., center line buffer area, lane, shoulder widths); and
- Create guidelines and a non−web-based tool to aid practitioners in implementing center line buffer areas.
Task 5. Prepare an annotated outline of the draft guidelines and draft concept for a non−web-based tool (e.g., a table, matrix, spreadsheet).
Task 6. Prepare Interim Report No. 1, which documents Tasks 1 through 5 and provides an updated work plan for the remainder of the research.
Phase I shall be limited to 6 months.
Work on Phase II of the project will not begin until authorized by the NCHRP.
PHASE II – Method Development
Task 7. Execute the method in the approved Interim Report No.1. Summarize findings in a technical memorandum.
Task 8. Develop the draft guidelines.
Task 9. Develop the draft tool with a user guide and examples.
Task 10. Prepare a draft virtual presentation for the AASHTO Technical Committee on Roadside Safety.
Task 11. Prepare Interim Report No. 2, which documents Tasks 7 through 10 and provides an updated work plan for the remainder of the research. Interim Report No. 2 is due no later than 6 months before the end of the contract.
Work on Phase III of the project will not begin until authorized by the NCHRP.
PHASE III – Final Deliverables
Task 12. Prepare final deliverables, including:
- Guidelines for implementing center line buffer areas;
- An implementation tool for practitioners with a user guide and examples;
- A final report, including an executive summary, that documents the entire research effort;
- A PowerPoint presentation with speaker notes that summarizes the project and distinctly illustrates for the audience how the research can be applied in their organization;
- A virtual presentation of the guidelines and tool for the AASHTO Technical Committee on Roadside Safety; and
- A technical memorandum titled “Implementation of Research Findings and Products”.
STATUS: Proposals have been received in response to the RFP. The project panel will meet to select a contractor to perform the work