NS753 - MnDOT Research & Innovation

NS753: Modernizing MnDOT's pavement deflection analysis method to accommodate both FWD and TSD data

Problem

Recognizing the huge potential of pavement deflection analysis, Minnesota Department of Transportation (MnDOT) has always played a big role in the development and refinement of deflection measurement and analysis tools, leveraging its unique MnROAD testing facility and collaborating with manufacturers and universities. MnDOT’s contributions span decades, beginning with early plate beam tests in the 1940s, Benkelman beam tests in the 1960s, and Falling Weight Deflectometer (FWD) methods in the 1980s. At each stage, MnDOT effectively built upon the lessons of earlier technologies to advance and promote the adoption of newer, more sophisticated tools. A prime example of this legacy is the TONN method—an empirical analysis based on decades of deflection data from Benkelman and plate tests. With the advent of FWD, MnDOT reimagined the method using a mechanistic-empirical framework, resulting in TONN2010. TONN2010 is one of the few FWD back-calculation programs capable of estimating temperature-adjusted seasonal pavement layer moduli, seasonal load-axle bearing capacities, and critical pavement damage accumulations. Its framework balances analytical rigor with practical efficiency, processing 100 deflection basins in just seven seconds on a standard computer.

Objective

The proposed work should consolidate and reassess past MnDOT deflection analysis studies, with a particular focus on the TONN method framework. By analyzing these methods and data, the study should recommend improvements to the TONN2010 method that address the key limitations outlined above, as well as any additional issues identified during the review. At minimum, the new software should expand the database and pavement typologies evaluated, and should also be capable to analyze both as TSD and FWD data

Previous research

Recently, MnDOT Research Office demonstrated that TONN2010 could be adapted for use with Traffic Speed Deflectometer (TSD) data, highlighting both the method's robust architecture and key limitations that need to be addressed through further research (Zegeye, Khazanovich, Smith, Lanotte and Dai, 2025 TRB conference/TRR Journal). This need calls for an improved deflection analysis methodology built on similar framework to TONN2010 and that addresses some or all the limitations of the TONN2010. To cite a few of the key limitations:

Framework: The new framework or architecture should as good as or better. It should include at least the same databases and embedded programs (or better ones).
Programming: TONN2010 is written in FORTRAN and packaged as a DOS executable, which is now incompatible with modern systems, causing frequent crashes. Updating the program using contemporary software would improve compatibility and stability.
Flexibility: The executable format makes it difficult to modify or update models and constant variables, limiting adaptability to evolving pavement designs and data sets.
Application: TONN2010 was designed for low-volume roads and produces accurate results only when pavement layer thicknesses match those specified in the program manual. This restricts its use on high-volume MnDOT highway projects.
Pavement System Compatibility: The program was built for traditional bituminous-on-aggregate base (BAB) pavement systems and does not support other systems used in MnDOT projects, such as full-depth bituminous (BFD) and bituminous-on-concrete (BOC).
Damage Models: The damage models were calibrated using limited road types and are not applicable to modern pavement types, such as reclaimed pavements and cold-in-place recycling.
Models: TONN2010 makes use of simulated FWD database. This database should be expanded and include also TSD database in such a manner to handle both data sources. It may be necessary to produce two separate databases for the two technologies using appropriate simulation programs
Traffic analysis: capable of generating ESALs for desired service years based on given AADTs
Final product: final product should be including layer mechanical properties, damage, bearing capacity and residual service life and other important parameters and critical pavement responses
Optional: Use of machine learning tools and GIS visualization tools

The Advances in deflection measurement technology—particularly improvements in Falling Weight Deflectometer (FWD) and the advent of Traffic Speed Deflectometer (TSD)—have significantly enhanced data collection, allowing for the measurement of hundreds of miles in a single day without disrupting traffic. However, the analysis and back-calculation of this data must improve to strengthen both project-level (scoping, design, forensic investigation) and network-level (periodic monitoring) pavement assessments.

Title(s) or short description of previous research:

MNDOT/UMN: Evaluation of Bearing Capacity of Low-Volume Roads in Minnesota Lev Khazanovich, Erland Lukanen, and Derek Tompkins
Transportation Research Record (2025): Efficient Mechanistic-Empirical Analysis of Traffic Speed Deflectometer Device Data for Network-Level Pavement Evaluation Eyoab Zegeye, Lev Khazanovich, Eleanor Smith, Michele Lanotte , and Shongtao Dai

Expected outcomes

New or improved decision support tool, simulation, or model/algorithm (software)

Expected benefits

The numbers 1 and 2 indicate whether the source of the benefit measurement is from:

A specific research task in your project that will be measuring this particular benefit, or
A separate effort to analyze data provided by the state or local agency involved in this project.

Operation and Maintenance Saving: (2)
- More accurate structural data will enable better treatment decisions, improving road longevity and ensuring more efficient use of budget resources.