BACKGROUND
Many states use AASHTO and the American Society for Testing and Materials (ASTM) standard specifications for their guardrail components. However, changes to the state of practice and to guardrail materials have created a need to revise AASHTO Standard Specification M 180-18, Corrugated Sheet Steel Beams for Highway Guardrail, and its associated material standards, including those referenced in M 180-18.
A lack of consistent standard specifications can increase fabrication costs for hardware suppliers and ultimately transportation agencies. A manufacturer can spend a significant amount of resources matching one state’s standard specifications only to start completely over to match those of another state. Consistency of specifications can also help to increase competition, allowing for the possibility of lower hardware costs for transportation agencies.
OBJECTIVES
The objectives of this research are to (a) perform a comprehensive review of AASHTO M 180- 18 and its associated AASHTO and ASTM standards and (b) propose needed revisions to bring the specifications into conformance with current requirements and the state of practice for highway guardrail systems. The revised standard shall specify—or refer to standards for—materials for components of the highway guardrail system, including beams, posts, end terminals, connecting hardware, etc.
TASKS
PHASE I – (Completed)
Task 1. Conduct a critical review of the literature on material requirements for highway guardrail systems.
Task 2. Develop and distribute an online survey of user groups to determine issues that the organizations have with generic highway guardrail system components.
Task 3. Analyze the results of the literature review and survey to prioritize deficiencies and outline the scope of revisions needed to remedy the deficiencies.
Task 4. Submit an interim report that documents the results of Phase I, presents a detailed work plan for Phase II, and includes at a minimum:
- The critical literature review (Task 1);
- The user group survey results (Task 2);
- Analysis of the deficiencies in the specifications prioritized as Urgent, High, Medium, or Defer. (Task 3); and
- Work plan for Phase II.
Note: Meet with NCHRP within 1 month of submitting the report to obtain approval to conduct the Phase II work plan.
PHASE II – (Completed)
Task 5. Execute the work plan approved by NCHRP and update as necessary. Develop a list of all proposed revisions. Propose changes to AASHTO M180-18 using redline and strikeout markup. Develop a companion commentary document. Propose revisions to associated ASTM material standards. Meet with NCHRP to obtain feedback on the proposed document revisions.
Task 6. Prepare a final version of the markups which reflect the changes requested by NCHRP.
Task 7. Submit a final report that documents the results, summarizes findings, draws conclusions, and presents (1) proposed revisions to AASHTO M180-18 and its associated standards for submission by NCHRP to COMP TS 4d and TCRS and (2) a list of all proposed revisions cross-referenced to supporting technical information in the final report . An appendix to the report shall include electronic files of all data used in the project and the results of the analyses conducted with the data.
PHASE III – Material Requirements for High-Tension Cable Barriers (Additional Scope of Work)
Task 8. Conduct a literature search and specification review on material requirements for highway HTCB systems. Low-tension cable barrier systems should also be included in this task. This should include, but not be limited to:
- Review of state departments of transportation (DOTs) standard specifications and standard details.
- Study of practices for installation, QA/QC, maintenance, etc. that are currently implemented by state DOTs.
- Review of the crash test reports and data for cable barrier systems.
Note: The selected contractor shall review all the qualification test reports for these barrier systems before ascribing engineering properties, and in particular, what alloys or non-metallic materials were selected by the manufacturers for their barrier systems.
Task 8a. Develop a revised state-of-practice survey questionnaire for state DOTs from the NCHRP Synthesis Report 493: Practice for High-Tension Cable Barriers, Appendix A.
Note: NCHRP approval of the revised survey questionnaire is required prior to deployment.
Task 9. Conduct the state-of-practice survey of state DOTs and compile results for panel review using the survey questionnaire revised from Task 8a. This survey is intended to be completed by each State DOT that uses HTCB in its median or roadside.
Task 9a. Conduct interviews with current HTCB suppliers to determine material and mechanical properties for HTCB components (as applicable) and to establish if there are common issues or ranges in state DOTs standards.
Task 10. Prepare a detailed work plan to develop a draft materials specification for HTCB systems for Phase IV that identifies and prioritizes material specification and acceptance program needs based on results of Tasks 8 through 9a. At a minimum, the work plan shall address the following to develop a draft specification for the engineering properties of the various steel components:
- The engineering properties for the various steel components for (1) posts, (2) cable, (3) cable-end treatments, (4) turnbuckles, and (5) other hardware.
- Appropriate geotechnical exploration and testing to derive critical geotechnical engineering design values.
- The AASHTO/ASTM test methods are relevant to determining engineering properties for the components that are specified.
- The method of acceptance for these components for (1) field inspection, (2) manufacturers' certification, (3) independent lab certification, and (4) sampling and testing by the owner.
If it is determined from Tasks 8 through 9a that an AASHTO material specification for HTCB would put undue restrictions on HTCB manufacturers, then a detailed work plan shall be made to develop a Cable Barrier Acceptance Plan for HCTB systems. At a minimum, the work plan shall address the following:
- Description of general cable barrier systems, terminology, and components.
- Material specifications for common steel components - cable
- The necessary geometric and concrete properties needed to specify anchors and post footings.
- Outline geotechnical exploration and testing requirements to ensure proper functioning of the systems.
- Guidance on material acceptance on-site (i.e., field inspection, manufacturers' certification, independent lab certification, or sampling and testing by the owner).
Task 11. Prepare Interim Report #1 documenting the results of Tasks 8 through 10 and provide an updated work plan for the remainder of the project. Following the review of the interim report by the NCHRP, the research team will be required to make a presentation to NCHRP.
Note: If an AASHTO Standard Specification is to be developed in Phase IV, NCHRP approval is needed before submitting to technical subcommittee 4D (Safety Devices) and TCRS for review and comments.
Note: The contractor will submit Interim Report #1 within 1 month of submitting the draft Phase IV scope of work to finalize the research plan. NCHRP approval of the interim report and the proposed Phase IV work plan is required before Task 6 begins.
PHASE IV- (Additional Scope of Work)
Task 12. Execute the Phase IV plan to develop draft specifications for AASHTO consideration of Cable Barrier Acceptance Plan. Develop draft specifications for the proposed revisions to associated material standards (if needed) or draft Cable Barrier Acceptance Plan and develop a companion commentary document. Submit the draft documents to the project panel for review.
Task 13. Prepare Interim Report #2. The report shall document the outcomes of Task 12 and be presented at a meeting with the NCHRP project panel. NCHRP approval of Interim Report #2 is needed before starting Task 14.
Note: If an AASHTO Standard Specification is developed in Phase IV, NCHRP approval is needed before submitting to technical subcommittee 4D (Safety Devices) and TCRS for review and comments.
Task 14. Revise the proposed draft AASHTO specifications or Cable Barrier Acceptance Plan considering the NCHRP’s review comments.
Task 15. Prepare a final deliverables package that documents the entire research effort of Phases III and IV. The deliverables should include, at a minimum (1) a research report documenting the work performed in Phases III and IV of the project, either (2a) the AASHTO Deliverable with draft text for consideration by AASHTO TCRS or (2b) the Cable Barrier Acceptance Plan intended to be distributed to state DOTs and other transportation agencies that utilize cable barrier on their medians or roadsides, (3) presentation material, and (4) technical memorandum on implementation (see Special Note B).
STATUS:
Phases I and II (Completed) - The final research report, including Appendices C through D, has been published as NCHRP Research Report 1020: Investigation of Material Requirements for Highway Guardrail Systems. Appendices A and B included proposed draft language that was submitted to AASHTO for consideration (https://store.transportation.org/Item/PublicationDetail?ID=5081)
Phases III and IV - The scope of work was expanded to include research for High-Tension Cable Barriers. Research in progress.
