| TTI Research Supervisor: Nathan D. Schulz, Ph.D. Associate Research Scientist Texas A&M Transportation Institute TAMU 3135 College Station, Texas 77843-3135 (979) 317-2694 n-schulz@tti.tamu.edu |
Pooled Fund Technical Representative: Scott U. Jollo, P.E. State Traffic Structures Engineer Traffic-Roadway Section Oregon Department of Transportation 4040 Fairview Industrial Dr SE, MS #5 Salem, OR 97302-1142 (503) 510-2204 Scott.u.jollo@odot.oregon.gov |
The American Association of State Highway and Transportation Officials (AASHTO) published an updated 2016 edition of the Manual for Assessing Safety Hardware (MASH) document (1). Along with this, the Federal Highway Administration (FHWA) and AASHTO developed a revised joint implementation agreement which establishes dates for discontinuing the use of safety hardware that has met earlier crash testing criteria for new installations and full replacements on the National Highway System (NHS). Although some barrier testing was performed during the development of the updated criteria, many barrier systems and other roadside safety features have yet to be evaluated under the proposed guidelines. Sign support systems were developed and investigated according to Test Level 3 (TL-3) criteria per previous NCHRP Report 350 standard requirements. Many of these systems have not been evaluated and crash tested under the current MASH Test Level 3 standard criteria. The purpose of this research is to evaluate a square tube slip base sign support system under MASH Test Level 3 testing and evaluation criteria. A critical configuration of the sign support system to be considered for full-scale crash testing will be selected through engineering analysis. Engineering opinion will be provided for less critical configurations of the sign support system. The information compiled from this research has the possibility to provide the FHWA and State Departments of Transportation with an acceptable sign support system under MASH Test Level 3 conditions.
The project objective is to evaluate MASH compliance of a critical configuration of a square tube slip base sign support system according to TL-3. Additionally, the TTI research team will determine MASH compliance of other less critical configurations through engineering analysis.
A successful design will allow agencies to use square tube slip base sign support systems on roadways as a MASH approved system.
The TTI research team will provide a final report that will include the results of the testing performed under the project and final design details of the square tube slip base sign support systems. Additionally, the TTI research team will provide engineering analysis and judgement for MASH compliance of other less critical configurations in the final report.
The work plan for this research includes the following tasks.
Task 1: Literature Review and Engineering Analysis
The TTI research team will perform a literature review of sign support systems that have been considered and tested in the past. The TTI research team will give particular relevance to slip base and square tube sign support systems. The TTI research team will also conduct a review of current state standards for slip base sign support systems with square tube posts. If needed, the TTI research team will conduct a survey of the Roadside Safety Pooled Fund states to gather more information on sign support sizes, sign sizes, and other installation details. There are many possible configurations of a sign support system. This includes variations in sign area, post size, attachments, and mounting height. As such, it is not feasible to evaluate every possible configuration of a sign support system with full-scale crash testing. The TTI research team will perform engineering analyses to select the critical sign support configuration for full-scale crash testing. The other less critical sign support configurations will be considered MASH compliant based on successful crash testing results.
Task 2: Crash Testing and Final Report
The TTI Proving Grounds will perform three full-scale crash tests on the sign support system according to MASH TL-3. One full-scale test will involve a 2,420-lb passenger car impacting the sign support system at 19 mph nominal speed with the face plane of the sign oriented perpendicular to the vehicle impact path. One full-scale tests will involve a 2,420-lb passenger car impacting the sign support system at 62 mph nominal speed with the face plane of the sign oriented perpendicular to the vehicle impact path. One full-scale tests will involve a 5,000-lb pickup truck impacting the sign support system at 62 mph nominal speed with the face plane of the sign oriented perpendicular to the vehicle impact path. The TTI research team will assess the crash tests according to the evaluation criteria set in MASH standards.
The TTI research team will generate a final report of the findings from the research and testing study. Results will be reported in terms of sign support system performance, vehicle stability, and occupant risk factors and will be compared with respect to MASH crashworthiness criteria. Recommendations will be provided for less critical sign support configurations evaluated through engineering analyses.
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