TSD for Network- and Project-based Applications

MnROAD | NRRA | Structure & Teams | ICT Team

Effective Use of Traffic Speed Deflectometer for Network-based and Project-based Applications

Status: Active
MnDOT Contract #: 1055530

Summary

To fully characterize the overall condition of pavements in the highway network and assess their maintenance and rehabilitation (M&R) needs, State Highway Agencies (SHAs) must employ practical data collection methods to evaluate the pavement surface condition as well as the pavement structural condition. The consensus is that incorporating the structural condition along with the surface condition into the pavement management decision-making processes can lead to better-informed and more cost-effective decisions. The limitations of the existing devices such as the Falling Weight Deflectometer (FWD), the device of choice for the backcalculation of layer properties and mechanical evaluation, and the desire to characterize the network-level structural condition have led to research efforts to investigate, validate, and demonstrate the effectiveness of Traffic Speed Deflectometer Devices (TSDs) in recent years. TSDs offer the advantage of improved operation safety, circumventing the need for temporary traffic control and lane closures, and increased spatial coverage over the stationary FWD.

This project focuses on developing analysis methodologies and guidelines for the classification of pavement sections using Traffic Speed Deflectometer (TSD) technology based on structural soundness categories and structural-based indices, and to evaluate the feasibility of TSD for project-based applications including backcalculation of modulus and calculation of the structural number (SN). The study aims to identify those indices meaningful for network and project-level applications and develop guidelines to identify those best suited based on the type of pavement. Several algorithms exist to provide the network-level and project-level information mentioned. However, none of them have considered the uncertainty of the data collected measurements related to the type and stiffness of the pavement type, and related to the TSD hardware and software.

The results of this study will be of particular value to SHAs to maximize their benefit-cost-ratio of using TSD by avoiding data collection on sections that are outside the useful range of operation of TSD and use the best algorithm to analyze the data collected that balances the uncertainties in the measurements and analysis.

The objective of this study is to provide solid guidelines and processes to SHAs on the best use of TSD to maximize the information extracted for their network- and project-level uses and minimize the cost of data collection.

Project Tasks

Task 1: Initial memorandum on expected research benefits and potential implementation steps

During the proposal phase and the development of the work plan, key benefits were selected to clearly define the benefits the state will receive from the results and conclusions of this research. This task will provide an initial assessment of research benefits, a proposed methodology, and potential implementation steps.

Deliverables: Task 1 (PDF)
Date due: August 15, 2024

Task 2: Document state of knowledge

This task will consist of the following four components:

During a half-day virtual meeting, the research team will present their overall concepts and approaches to the Team Advisory Panel (TAP) and will seek their advice on the appropriateness of the scope and tasks. Based on the feedback received, the work plan will be modified to ensure practical and useful outcomes. Additional virtual meetings with the TAP will be held at the project mid-point and near the end of the project to report progress and request feedback.
With the help of TAP, a questionnaire will be developed and broadly distributed among the users of TSD to obtain information about the best-perceived uses of TSD, their hands-on or second-hand experience with the TSD operation, and data quality, management, and processing. The TSD User’s Group members and the DOTs will be the target of this survey. The research team will summarize and discuss the results with the TAP to set the direction of the efforts.
The research team will concisely document the state of knowledge and the state of practice and the latest advancements related to network-level and project-level applications of TSD. Alternative analysis approaches advocated by different institutions will be reported with their preliminary strengths and weaknesses. Case studies will be documented along with an initial assessment of research benefits.
Based on the knowledge gained in the first three items, the possible applications of the TSD will be prioritized to maximize the benefits of this study to the NRRA members.

Deliverables: Technical memorandum documenting the state of knowledge, and historical case studies, and documentation of the existing methodologies.
Date due: October 31, 2024

Task 3: Gap and SWOT analysis of TSD-related adoption

To delineate strengths, application opportunities, and existing gaps regarding TSD integration to network-level and project-level operations, the research team will carry out comprehensive gap and SWOT analyses considering data components that complement Time-Speed-Distance (TSD) data for a complete structural evaluation, parameters needed in decision trees for treatment selection, and data quality control during TSD data collection and post-processing.

In addition, an assessment of the network-level TSD application prioritized in Task 2 will be conducted using a relevant subset of existing data recently collected in Minnesota as part of the Transportation Pooled Fund TPF-5(385) and data collected under NCHRP Project 10-105 in 2021 at MnROAD. The additional information collected by State staff with respect to pavement conditions in the form of condition scores or distress ratings, along with other pavement type descriptors and Ground Penetrating Radar (GPR) thickness and Falling Weight Deflectometer (FWD) deflection data State staff will also be used. If based on the results from Task 2 additional sources of data are deemed necessary, the Research Team in collaboration with TAP members will approach the other DOTs participating in the pooled-fund study. The furnished data will undergo preliminary data analysis to assess data reduction and data processing, deflection indices, and deterioration trends using descriptive statistics. Existing thresholds of deflection indices (as provided in the literature) will be evaluated for the categorization of structural soundness and propose a framework to categorize pavement structural soundness using TSD data while considering the pavement type and deterioration level.

Concurrently, the research team will also evaluate the State TSD data to assess the potential of TSD technology to be utilized for project-level applications prioritized by TAP as part of Task 2. The analysis will consist of a preliminary assessment of how TSD measurements (i.e., TSD deflections and/or deflection-based indices) along with existing models can be used to characterize the pavement structure, establish thresholds, and estimate the in-situ layer moduli via backcalculation for different pavement types. Correlation and trend analyses will be conducted to identify those pavement structures or conditions that may lend themselves as being more suitable for project-level and network-level applications.

Deliverables: A memorandum containing a gap analysis of available data and current procedures to incorporate TSD information in the classification of pavement structural soundness, as well as the necessary components to perform project-level analysis for design and forensic purposes. Field case studies describing sites condition and reduced measurements from TSD and preliminary results including descriptive statistics of case studies with TSD collected data and other relevant test devices supplementing the experimental tests.
Date due: February 28, 2025

Task 4: Development of draft initial guidelines for TSD adoption

Using the outcomes of Tasks 2 and 3, draft guidelines for instituting TSD for project-and
network-level operations will be proposed. The guidelines will address the following two items:

A detailed methodology and step-by-step guidance on how to incorporate TSD to identify/classify structural soundness categories at a network level.
Analysis of TSD information, selection of candidate deflection indices, estimation of structural number or equivalent, and identification of “soft spots.”

Based on information and knowledge obtained in Tasks 2 and 3, the research team will develop application-specific TSD data collection protocols and supplementary test data for supporting feasible network-level and project-level applications to achieve the two items just enumerated. Supporting data may include condition and distress ratings, functional information, material properties, and pavement structure, among other information collected from additional testing such as the FWD and GPR. Distinct pavement structures (both flexible and rigid) with different geomaterials will be considered to assess the effectiveness of TSD toward network and project-level applications. The most practical strategies for the analysis of the data for the feasible network-level and project-level applications will also be laid out. This plan will be shared with the TAP to obtain feedback and accommodate modifications that best suit NRRA members’ field operations and data analysis cultures. If the TAP deems it beneficial, the research team may instrument a test section to evaluate the accuracy of the TSD measurements. The plan will also inform NRRA members of the data necessary from field test cases that will serve as supporting data for TSD validation.

Deliverable: A memorandum containing a plan with recommendations for data collection protocols that will support MnDOT data collection procedures and draft guidelines for instituting TSD for PMS operations
Date due: March 31, 2025

Task 5: Analysis of field data to assess TSD guidelines

The collected data by State not used in Tasks 3 and 4 will be analyzed to ensure the practicality and accuracy of the revised recommended guidelines for network- and project-level procedures. This task will also verify how TSD measurements correlate with the FWD and evaluate existing models to predict the structural condition, backcalculated moduli, and structural and functional performance of the pavement sections. The research team will make use of FWD, GPR, and other relevant testing collected by State to verify the suitability of TSD measurements given their uncertainty and variability for the type of pavement and condition, and that the developed models and/or procedures predict the structural condition, backcalculated moduli, and the structural and functional performance of the pavement sections. The research team will also aim to refine the proposed methods and analysis procedures. This process will be carried out through rigorous statistical and reliability approaches for defining the risks and benefits of the different methods proposed, as well as their limitations. A list of recommendations will be developed to implement and/or supplement the proposed methodologies. An assessment of the feasibility of using TSD for project-level applications will also be documented.

Deliverable: Memorandum with preliminary draft guidelines for adoption of network-level operations and project-level applications. Analysis results of the field studies including validation of models, evaluation of deflection-based indices, evaluation of thresholds, and any additional correlation with other relevant test devices supplementing the experimental tests such as FWD deflection bowls, will be documented.
Date due: October 31, 2025

Task 6: Refine proposed TSD guidelines

Following the analysis and findings of the data collected in the field case studies and the amendment and/or refinement of the methods proposed, the research team will draft revised guidelines for the use of TSD. Guidelines will be developed for using TSD for network-level applications, which will include:

Detailed methodology and step-by-step guidance on how to incorporate TSD to identify structural conditions using representative indices and to classify pavement into an appropriate structural soundness category at a network level, e.g. using deflection basin indices thresholds. This method shall also include the integration of pavement surface conditions and functional performance parameters.
Methodology to extract TSD information (e.g., structural adequacy, moduli) for PMS integration.

Guidelines will be developed for using TSD for project-level applications for types of pavements identified as promising for implementation. The drafted guidelines will provide:

Detailed step-by-step method to backcalculate in situ layer modulus using deflection-basin indices.
Methodologies for calculating structural condition index and effective structural number.

A roundtable will be facilitated to obtain feedback from the TAP about the developed guidelines. The roundtable will be made through a webinar to accommodate more personnel and encourage more contributions. The research team will open the discussion with a brief overview of the scope of the project and will continue with an overview of the guidelines with the proposed framework to use TSD data useful for network-level applications. Feedback obtained from attendees will be documented to ensure that the guidelines will be of benefit to the endusers. At this stage, the guidelines will also be modified to address as many of the concerns as possible.

Deliverable:A technical memorandum with the refined proposed guidelines for TSD integration for network-level operations, and project-level applications, as well as recommendations for integration to PMS.
Date due: December 31, 2025

Task 7: Final memorandum on research benefits and implementation steps

During earlier phases of the project, key benefits were selected to clearly define the benefits the State of Minnesota will receive from the results and conclusions of this research. This task will produce a final memorandum that clarifies and documents the methodology used to calculate benefits, including any assumptions and steps required. In addition to quantitative calculations (when feasible), this task should also include a qualitative discussion of the estimated benefits. The memorandum should also include key steps that agencies could take to implement the research.

Deliverable: A final technical memorandum at the end of the project that provide details of the methodology, steps, and approach for evaluating benefits, benefits quantification results, and discussion of next steps for implementation.
Date due: December 31, 2025

Task 8: Draft report, Technical Advisory Panel review, and revisions

A draft project report summarizing the results, findings, conclusions, and recommendations of the research will be delivered. The report will comply with State’s Editorial guidelines. The report will include an implementation plan for improving and deploying the products of the research and a draft specification in AASHTO format. Upon the feedback of the TAP, the final report will be finalized for delivery.

Deliverable: A draft report
Date due: February 28, 2026

Task 9: Editorial review and publication of final report

During this task, the PI will work directly with State’s contract editors to address editorial comments and finalize the document in a timely manner. The contract editors will publish the report and ensure it meets publication standards.

Deliverable: Final Publishable Report that meets State’s editorial guidelines and standards
Date due: April 30, 2026

Project team

Email the Project Team
Principal Investigators: Soheil Nazarian, nazarian@utep.edu; Cesar Tirado, ctirado@utep.edu ; and Rajib Mallick, rbmallick@utep.edu, UTEP
Technical Liaison: Eyoab Zegeye, MnDOT, eyoab.zegeye@state.mn.us
Project Technical Advisory Panel (TAP): Contact us to join this TAP

Tim Anderson, MnDOT
Emil Bautista, MnDOT
Gabriel Bazi, Pulsuus
Tom Burnham, MnDOT
Shongtao Dai, MnDOT
Jerry Daleiden, ARRB Systems
Steve Henrichs, MnDOT
Micah Holzbauer, MnDOT
Mike Lanotte, Michigan State University
Joseph Podolsky, MnDOT
Marcos Sanchez-Pliego, MnDOT
Nicholas Schaefer, Surface Systems and Instruments
Nadarajah "Siva" Sivaneswaren, FHWA
Dave Van Deusen, MnDOT
Eyoab Zegeye, MnDOT (TL)

Related Materials

Initial project proposal (PDF), 5/5/2023
Workplan (PDF), 4/9/2024