BACKGROUND: Traffic Speed Deflection Devices (TSDDs) that measure surface deflection at traffic speeds are used by several highway agencies in the United States and other countries to provide data to help with management of the highway network. For example, these data can be used for assessment of pavement structural condition, selection of pavement treatments, and other purposes. In comparison with traditional pavement deflection measurement (e.g., falling weight deflectometers), TSDDs provide a means for acquiring extensive amounts of data in a short period of time. However, the data obtained from TSDD measurements are influenced by many factors such as pavement type, pavement structure, climatic conditions, and speed of operation. Recognizing that no widely accepted practices for verifying the measurements obtained by TSDDs is currently available, research is needed to identify the deflection measurements that are required for pavement structural assessment and other applications and develop a procedure for verifying TSDD measurements and also to develop a recommended standard practice for implementing this procedure.
OBJECTIVE: The objective of this research is to develop a recommended standard practice for verification of the measurements obtained by TSDDs on highway pavements for consideration and adoption by AASHTO.
Accomplishment of the project objective will require at least the following tasks.
PHASE I: (1) Collect and review relevant domestic and foreign literature, research findings, and information relative to TSDDs’ measurements. This information may be obtained from published and unpublished reports, and contacts with public and private organizations involved in the collection of traffic speed deflection data. (2) Based on the review performed in Task 1, identify the deflection measurement characteristics (data elements and parameters) that are required for pavement structural evaluation and other applications as well as those items that affect these characteristics for further consideration/investigation in Phase II. (3) Based on the evaluations performed in Task 2, prepare an updated, detailed work plan for Phase II, that includes an approach for developing a procedure for verifying the identified deflection measurement characteristics and developing a recommended standard practice for implementing the procedure. The proposed approach shall include field experiments of various TSDDs and cover a range of those items that affect the data obtained from TSDDs. (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 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.
PHASE II: (5) Execute the Phase II plan approved in Task 4, and develop the verification procedure. (6) Prepare a recommended standard practice for verification of the deflection characteristics obtained from TSDD measurements, in AASHTO format. (7) Prepare a final deliverable that documents the entire research effort. The recommended standard practice shall be prepared as stand-alone document.
Status: Research in progress.