Pavement deflections obtained from falling weight deflectometer (FWD) measurements and roughness obtained from longitudinal profile measurements are used together with other measurements to assess pavement condition and performance. These measurements are influenced by the temporal and/or diurnal variations; their consideration is necessary for accurate assessment of pavement condition.
The Long-Term Pavement Performance Program (LTPP) Seasonal Monitoring Program (SMP) was initiated to obtain data on the influence of temporal variations on pavement deflection and roughness. However, the temporal and diurnal data contained in the LTPP database (see Special Note A) have not been applied to improve the practices of measuring deflection and roughness, and their use has not been demonstrated. Also, recent work completed under NCHRP Project 20-50(22), “LTPP Data Analysis: Feasibility of Using LTPP data to improve Use of FWD and Longitudinal Profile Measurements” identified some of the issues related to the use of FWD and longitudinal profile measurements and proposed a preliminary research plan for addressing these issues (see Special Note B). However, additional research is needed to further define and address the issues associated with the effects of temporal and diurnal variations on FWD and longitudinal profile measurements, and to develop guidelines to improve these measurements and their use in evaluating pavement condition.
The objective of this research is to develop guidelines for improved use of FWD and longitudinal profile measurements data in evaluating pavement condition by considering the effects of temporal and/or diurnal variations. The research shall address both asphalt and concrete pavements and focus on using the data available in LTPP database (including those for SMP test sections).
The NCHRP is seeking the insights of proposers on how best to achieve the research objective. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must present the proposers' current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objective. Task descriptions are intended to provide a framework for conducting the research.
Accomplishment of the project objective will require the following tasks.
Task 1. Identify the effects of temporal and diurnal variations on FWD and longitudinal profile measurements, and propose approaches for investigating these effects. Recommend approaches, for further investigation in Phase II, to aid in developing guidelines for improved use of FWD and longitudinal profile measurements.
Note: Proposals shall include the research team’s current thinking regarding the process for identifying the approaches proposed for investigating the effects of temporal and/or diurnal variations, and the rationale for selecting those recommended for further investigation.
Task 2. Review the content of the LTPP database, and assess adequacy of the data elements available in the LTPP database to support the approaches recommended in Task 1 (in terms of data type, quantity, quality, and other relevant criteria). If required, identify other sources of data to supplement LTPP data (e.g., data from other experimental test sections). Assemble the data needed to execute the proposed investigations and develop the guidelines.
Task 3. Prepare an updated, detailed work plan for executing the recommended approaches and determining the effects of temporal and/or diurnal variations on FWD and longitudinal profile measurements, and developing the guidelines. The plan shall also include an outline of the proposed guidelines.
Note: Proposers must include in the proposal a plan that provides detail on the proposer’s current thinking regarding the work anticipated in Phase II for investigating the effects of temporal and/or diurnal variations and developing rational guidelines for improved use of FWD and longitudinal profile measurements. The work proposed for Task 5 must be divided into subtasks, and proposers must describe in detail the work proposed in each subtask.
Task 4. Prepare an interim report that documents the research performed in Tasks 1 through 3. Following review of the interim report by the NCHRP, the research team will be required to make a presentation to the NCHRP project panel. Work on Phase II of the project will not begin until the interim report is approved and the Phase II work plan is authorized by the NCHRP. The decision on proceeding with Phase II will be based on the contractor’s documented justification of the updated work plan.
Note: The contractor shall submit the Phase I interim report within 8 months from contract award and meet with NCHRP within 2 months of report submission. The meeting is expected to be in-person and held in Washington, DC. Whether in-person or online, NCHRP will host the meeting and be responsible for any panel member costs to attend meeting.
Task 5. Execute the Phase II plan approved in Task 4. Based on the results of this work, prepare guidelines for improved use of FWD and longitudinal profile measurements data in evaluating pavement condition that incorporates consideration of the effects of temporal and/or diurnal variations.
Task 6. Prepare a final deliverable that documents the entire research effort. The proposed guidelines shall be presented as a stand-alone deliverable in a format appropriate for consideration and adoption by AASHTO. All relevant data sets identified in this research (including those available from LTPP database and other sources) shall be provided, in an electronic format with schema, as an attachment to the final deliverable.
Status: Proposals have been received in response to the RFP. The panel will meet to select a contractor to perform the work.