The objective of transportation pooled fund study TPF-5(332) LTPP Pooled Fund that concluded in June 2021 was to perform forensic evaluations on Long-Term Pavement Performance (LTPP) test sections as they went out of service, in general accordance with the guidelines provided in the Transportation Research Board’s National Cooperative Highway Research Program (NCHRP) Report 747: “Guide for Conducting Forensic Investigations of Highway Pavements.” When the referenced study commenced in 2017, there were approximately 750 active LTPP test sections. And, by the time the study was completed on June 30, 2021, forensic evaluations had been carried out on 63 test sections at 26 different locations and in 23 different states. This study yielded important benefits to the participating States including: • Insight into the factors that produce good or poor performing pavements. • Understanding of how LTPP data can be used to further benefit the State’s pavement engineering operations. • Demonstration of how a forensic study of a pavement test section can be carried out to be further used in the State’s pavement engineering practices. This project had the added benefit of reviewing the adequacy of the data contained in the LTPP database to explain the performance of the test sections. The study yielded many important findings that contributed to improving the LTPP data both in terms of completeness and quality. Other key study findings included the importance of obtaining within test section thickness measurements via coring or other means and the need to interact with the appropriate State highway agency (SHA) staff, via interviews and meetings, to better understand the performance of the test sections. Having measured thickness data within the limits of the pavement area monitored – i.e., not outside of the test section – is critical to the understanding of performance. Likewise, having a clear picture of the construction, maintenance, rehabilitation, and traffic history of the test sections, which no one knows better than the respective SHA personnel, is also critical to the understanding of performance. At present, approximately 336 active test sections in 31 states remain in the LTPP program. As these sections reach their useful life or as they are taken out-of-study for various reasons, understanding how they performed and why they performed as they did must continue to be determined through forensic review. Given the benefits to LTPP stakeholders and the program derived from the conduct of forensic investigation of test sections going out of study, especially in terms of data completeness and quality, it is important that the forensics work continue.

The objective of the proposed pooled fund study is to create a mechanism to allow for rapidly completing forensic evaluations of LTPP sections before going out of service. Test sections that are no longer active, but which have remained unchanged (i.e., no maintenance or rehabilitation has been applied), may also be considered for forensic evaluation. Possible reasons for carrying out the forensic evaluations include: • Determining reasons for poor pavement performance/premature failures • Understanding exceptional pavement performance and/or longevity • Validating pavement performance prediction (predicted vs actual) • Collecting data to support development and/or calibration of pavement performance prediction models • Closing-out/conducting final investigations of experimental test sections Ultimately, however, the primary reason for carrying out the evaluations will be to determine if the data contained in the LTPP database adequately explains the performance of the test sections and why they performed as they did.

PLEASE SEE ATTACHED WORKPLAN FOR DETAILS 

The ultimate aim of this proposed stage 2 pooled fund study is aiming for 10 to 15 states, each contributing a minimum of $20,000 per year for a minimum of three years. It is anticipated that FHWA, other agencies, and industry may also participate in the pooled fund. To initiate this study a threshold budget of $200,000 is proposed that is estimated to be outlaid as follows in order to get the study started:

1. $25,000 - Project Management.
2. $10,000 - Test section selection.
3. $175,000 - Desktop Studies and Tech Memoranda (estimate around 9); Follow-up forensic investigations each concluding with an updated Tech Memorandum (estimate around 3).
4. $15,000 - Final Report aligned with that prepared for the TPF5-332 LTPP study recently completed.
5. $15,000 - Travel, etc.

Activities under Tasks 2 and 3 are to be carried out in accordance with the guidelines contained in NCHRP Report 747. Depending upon commitments and obligations actually made we may be able to expand the number and scope of these.

Here is a list of states that active test sections currently exist--with an appeal that they please join this pooled fund as they may benefit greatly: 1. ARIZONA 2. ARKANSAS 3. CALIFORNIA 4. COLORADO 5. FLORIDA 6. GEORGIA 7. IDAHO 8. INDIANA 9. IOWA 10. KANSAS 11. MANITOBA 12. MISSISSIPPI 13. MISSOURI 14. MONTANA 15. NEVADA 16. NEW MEXICO 17. NORTH CAROLINA 18. NORTH DAKOTA 19. OHIO 20. OKLAHOMA 21. ONTARIO 22. OREGON 23. PENNSYLVANIA 24. RHODE ISLAND 25. SOUTH CAROLINA 26. SOUTH DAKOTA 27. TEXAS 28. UTAH 29. VIRGINIA 30. WASHINGTON 31. WISCONSIN