BACKGROUND

The 2016 AASHTO Manual for Assessing Safety Hardware (MASH) provides full-scale test matrices for evaluating cable median barriers on level terrain and sloped median ditches. The matrices define the critical placement of cable barriers and test criteria for 4:1 (horizontal to vertical slope) and 6:1 V-ditches to evaluate the safety performance of cable median barriers. Recent full-scale crash testing of cable median barriers under the conditions described in MASH Test No. 3-16 have produced varying results for the stability of small vehicles traversing 4:1 V-ditches.

MASH Test No. 3-16 uses a 46-ft-wide V-ditch as measured from slope break point to slope break point, with the cable barrier test article placed 4 ft from the slope break point on the far side of the V-ditch. However, small vehicles have experienced inconsistent stability while traversing the 4:1 V-ditches during crash testing, and the AASHTO Roadside Design Guide (RDG) notes that 4:1 V-ditches are not a preferred configuration for median V-ditches. This raises concerns that the traversability of the V-ditch configuration used in MASH 2016 may be near the limit of vehicle stability.

Research is needed to investigate the traversability of 4:1 V-ditches to verify if the current configuration specified in MASH Test No. 3-16 produces sufficient vehicle stability for consistent and reliable test article impact conditions.

OBJECTIVE

The objective of this research is to investigate the traversability of 4:1 V-ditches for crash testing of cable median barrier systems.

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

TASKS

PHASE I – Planning

Task 1. Conduct a literature review of relevant research and other sources regarding the traversability of 4:1 V-ditches and other 4:1 ditch geometries with a focus on the traversal behaviors and trajectory of the MASH 1100C vehicle, but also considering the 1500A and 2270P test vehicles. The review shall include published and unpublished research conducted through the NCHRP; the Federal Highway Administration (FHWA); and other national, international, state, and pooled fund sponsored research.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 department of transportation (DOT) standards, the RDG, MASH, and other published guidelines regarding 4:1 ditch geometries.

Task 3. Synthesize and summarize the results of Tasks 1 and 2. Define the knowledge gaps relevant to the project objective that will be addressed in this research. Document the findings of Tasks 1 through 3 in a technical memorandum.

Task 4. Develop a method to achieve the project objective, to be executed in Phase II. At a minimum, the method shall formulate strategies to:

• Define ditch traversability and vehicle stability prior to impacts with cable barrier for consistent and repeatable crash test results
• Determine evaluation criteria to meet the definitions of ditch traversability and vehicle stability
• Determine critical factors and their effects on 4:1 V-ditch traversability and vehicle stability associated with
  • soil conditions
  • ditch width
  • vehicle trajectory
  • vehicle parameters
  • other relevant factors identified by the researcher
• Investigate the performance differences between 4:1 V-ditches and 4:1 round bottom and 4:1 flat bottom ditches
• Verify if the 4:1 V-ditch configuration specified in MASH is traversable in a consistent manner for full-scale testing using simulation and physical testing (physical testing may or may not require a test article, i.e., cable barrier)

Task 5. Prepare Interim Report No. 1, which documents Tasks 1 through 4 and provides an updated work plan for the remainder of the research.

PHASE II – Method Development

Task 6. Execute the method in the approved Interim Report No.1 except for modeling, simulation, and physical testing. Provide an updated plan for modeling, simulation, and physical testing to verify that the 4:1 V-ditch configuration specified in MASH is traversable based on the findings/feedback of the method. Summarize findings in a technical memorandum and participate in a virtual meeting to debrief the NCHRP panel.

Task 7. Execute modeling and simulation. Document findings in a technical memorandum and participate in a virtual meeting to debrief the NCHRP panel. If needed, revise the physical testing plan. NCHRP approval is required before physical testing in Task 8 can begin.

Task 8. Execute physical testing. Document findings in a technical memorandum.

Task 9. Validate and, if necessary, refine the definitions for ditch traversability and vehicle stability. Determine if the 4:1 V-ditch configuration specified in MASH is acceptable. Based on the validation results, develop a stand-alone document with the refined definitions and MASH language for AASHTO consideration and other supporting materials (hereafter called AASHTO deliverables). This resulting language may be considered by AASHTO for the next updates of MASH and the RDG.

Task 10. Develop an outreach plan to gather feedback from the AASHTO Technical Committee on Roadside Safety (TCRS), the TRB Committee on Roadside Design, or a similar industry group with a minimum of one presentation, to be executed in Phase III. The presentation(s) and other activities in the outreach plan shall be hosted and coordinated by the research team.

Task 11. Prepare Interim Report No. 2, which documents the results of Tasks 6 through 10 and provides an updated work plan for the remainder of the project.

PHASE III – Final Deliverables

Task 12. Execute the outreach plan per the approved Interim Report No. 2. Summarize activities and findings in a technical memorandum.

Task 13. Revise the AASHTO deliverables. The AASHTO deliverables are due at least 6 months before the contract end date.

Task 14. Prepare final deliverables, including:

• A research report, including an executive summary, that documents all research, findings, and project efforts;
• The AASHTO deliverables;
• 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;
• Supporting data files, including photos and videos; and
• A technical memorandum titled “Implementation of Research Findings and Products”.

STATUS: A response has been received for this RFP. The project panel will meet to determine next steps.