most important of which is in support of AASHTO’s pavement mechanistic-empirical design (PMED) software. Annual federal funding for data collection averaged $11.5 million from inception through 2014, after which it declined to half or less annually.

The LTBP program was authorized by Congress in 2005 and was intended to be a parallel effort for bridges to the LTPP program. Although it began as a federal initiative, the LTBP developed a similar approach to the one used by the LTPP. In collaboration with state DOTs, FHWA developed a large sample of typical, representative bridges of most interest to states in different regions and set priorities for the types of bridge data to be collected. Funding levels for the program were approximately $10 million annually. The LTBP placed initial, but not exclusive, emphasis on bridge deck performance and measurement of deck condition using non-destructive evaluation (NDE) technologies. The LTBP embarked on a sustained effort to develop a robotic device that could collect a suite of NDE deck measures simultaneously and efficiently. A prototype system was developed and data were collected on 38 bridges. However, when the program scaled up to collect data on a broader sample, issues were encountered regarding data repeatability and device durability. In addition, the slow pace of data collection required lane closures for several hours—more than state DOTs could support except on low-volume bridges. In recent years funding for the LTPP and the LTBP, combined, has fallen below $8 million.

The main thrust of the LTIP program in recent years has been to improve access to existing pavement and bridge performance data for the research community. The latest release is the InfoHighway portal™,¹ which provides access to the LTIP’s other data and information portals, namely InfoPave™, InfoMaterials™, InfoBridge™, and InfoTechnology™. InfoPave includes the LTPP data as well as data from MnRoad (see the section Highlights of Program Progress During 2022) and other pavement performance databases. InfoMaterials includes data from materials experiments carried out by FHWA as well as data collected from tests of state DOT mix designs and materials through FHWA’s mobile testing facilities. InfoBridge contains general condition ratings from visual inspections of the roughly 620,000 bridges in the National Bridge Inventory (NBI) as well as limited National Bridge Element data for 249,000 bridges. Also included are NDE data collected by the LTBP on 38 state DOT highway bridges. InfoBridge has data visualization tools that allow users to map specific bridges and view trends over time at the bridge or inventory level. The LTIP developed and added two bridge deterioration models based on NBI general condition ratings (discussed further below). InfoTechnology includes guidance materials compiled by FHWA’s NDE Laboratory for state DOT practitioners on NDE data collection methods and technologies.

HIGHLIGHTS OF PROGRAM PROGRESS DURING 2022

Field Data Collection on Infrastructure Performance

Pavement Performance Data Collection

As noted, most of the effort within the LTPP is to complete data collection following a general approach established roughly 30 years ago. Most of the LTPP test sections included in the InfoPave portal address the long-term performance of different designs and materials associated

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with flexible and rigid pavements. With some exceptions, however, the LTPP does not include the kinds of new materials that states are experimenting with for overlays to extend pavement service life. Two pavement performance experiments designed by the LTPP² that would have helped in this regard were not implemented due to a lack of funds. The LTPP staff have been actively encouraging and supporting a state-led, pooled-fund project (described below in the subsection Collaborations with States, Pooled-Fund Studies) that would move these experiments forward.

Bridge Performance Data Collection

Around 2020, the LTIP decided to end its robotic NDE data collection effort, which had been dormant since 2018. Given the need to re-align its field data collection approach, in 2021 the LTIP held a virtual workshop with the assistance of the LTIP Bridge ETG members and with participation of state DOT bridge professionals and other experts from academia and industry. The workshop identified priorities for data collection on bridge performance and existing NDE technologies for collecting such data, preferably without closing lanes.³ The LTIP staff are following up on a major outcome of the workshop (discussed below in the subsection Outcomes of 2021 Bridge Data Workshop), which includes determination of existing bridge performance data that states have that could be collected by the LTIP. However, progress in bringing on a new contractor to carry out this project was stymied by a lack of a 2023 appropriation for the U.S. Department of Transportation until late 2022. The LTBP continues as a formal FHWA RD&T activity, but the LTIP staff do not consider federal collection of field performance data to be part of it at current levels of funding.

Accelerated Testing

Pavements

A new source of data on the performance of new in-service materials may result from FHWA RD&T’s new accelerated pavement test (APT) facility. The APT facility will be managed by an FHWA RD&T office that is separate from the LTIP, but the data from the APT will be made available to researchers through InfoPave. FHWA has procured new accelerated loading machines to replace its outdated, full-scale, accelerated loading facilities.⁴ The APT facility will become operational during 2023. Depending on the materials chosen for testing, the APT facility output has the potential to help states address the performance of materials (overlays) they are using, including those with varied percentages of recycled materials. The LTIP is defining the data and formats for inclusion in InfoPave.

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Bridges

Testing at the Rutgers University Bridge Evaluation and Accelerated Structural Testing (BEAST) laboratory continued in 2022. The laboratory can apply rolling loads, simulate freeze-thaw cycles, and apply brines to simulate deicing treatments. The LTIP is sharing in the funding of BEAST testing a 50-foot, single span, reinforced, concrete deck supported on steel beams. The activity, so far, has two phases of testing. Phase 1, completed in 2021, applied rolling load, freeze-thaw cycles and brine to a bare concrete bridge deck. Methods of evaluation of the deck included visual inspection, ultrasonic tomography, surface electrical resistance (Wenner probe), and high-resolution imaging. At the end of testing, the deck had spalls on more than 17 percent of the area of its top surface. Phase 2, now in progress, applies rolling loads, freeze-thaw cycles, and brine to the same deck after repair with overlay. Two overlays were installed. Latex-modified concrete was installed on one half width of the deck due to its widespread use by state DOTs. Ultra-high performance concrete was installed on the other half due to FHWA’s interest in promoting the use of this product. Testing is in progress and expected to continue through most of 2023.

All NDE, sensor, and visual inspection data from this project, which have been collected at regular intervals, will be posted in InfoBridge at the end of the project. NDE data will be presented in raw format rather than processed form.

Coatings and Corrosion Laboratory

The FHWA coating and corrosion laboratory is performing studies on the performance of coatings, stress-corrosion cracking in stainless steel, the use of duplex coatings in preventive maintenance, and the performance of prestressing strands exposed to chlorides and sulfates. Completed and emerging results were presented to the Bridge ETG. The LTIP staff proposed gathering field data on state DOTs’ experience with stainless steel reinforcement in bridge decks to determine whether corrosion found in the laboratory is being experienced in the field, to which the committee returns in the section Assessment of Pavement and Bridge Activities During 2022.

Collaborations with States

Pooled-Fund Studies

MnRoad,⁵ which includes the Minnesota DOT test track, is currently in a partnership with the National Center for Asphalt Technology. It is testing a number of pavement preservation techniques through a pooled-fund project supported by 17 states and numerous other organizations. This pooled-fund project is in the process of being renewed with more than 20 states expected to be included.⁶ The LTIP staff are coordinating with the pooled-fund project and will continue to host data as they are collected. This pooled-fund project may implement the two LTPP experiments on pavement performance mentioned above that were not previously funded. The LTIP staff are also actively supporting the continuation of a state-led, pooled-fund project conducting forensic analyses of LTPP test segments that have failed in order to better understand

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how and why they failed. The first phase of the project ended successfully and a second phase to conduct more forensic analyses is being planned.⁷

LTPP Climate Data for AASHTO PMED Software

In addition to the above efforts, during the past year, the LTIP developed an interface to automatically gather the climate data in the LTPP (from the National Aeronautics and Space Administration’s Modern-Era Retrospective Analysis for Research and Applications Version 2 [MERRA-2]) and add it to the AASHTO PMED software. State DOT pavement designers using PMED software will no longer have to undertake this step manually.

Improved Data Accessibility

Recent LTIP efforts have focused on making the datasets available through the portals described above easier to access, assemble, and use. The stated intent is to have researchers and other interested parties focus more of their time and energy on analyzing the data rather than assembling the data they need. The first effort, completed in mid-2022, (a) assembled data and variables on specific materials properties included in the LTPP database that are scattered in various tables and (b) developed models to impute values for missing data. The Analysis-Ready Materials Dataset (ARMAD) released this year contains roughly 1 million records.⁸ The ARMAD also defines and classifies materials properties and data layers needed for the AASHTOWare PMED software. Now that the dataset is assembled, it will be updated as the performance data collected from the remaining LTPP test sections are added to the LTPP database.

The LTIP staff are currently developing additional accessible databases for LTPP users. The next effort will focus on creating an Analysis-Ready Performance Database that gathers all available measures of performance (surface distresses, surface characteristics, surface deflections, and various computed parameters). The LTIP Pavements staff have developed and circulated a white paper that describes the planned approach, particularly for dealing with anomalous data and outliers.

NDE State of the Practice

The InfoTechnology portal provides state-of-the-art guidance information to practitioners on NDE techniques and technologies appropriate for assessing different types of issues and conditions for various infrastructures (mainly pavements, bridges, and tunnels.) The NDE Laboratory has been assisting a state pooled-fund study that is building on SHRP 2 RO6C research on ground-penetrating radar approaches to measure asphalt pavement compaction.⁹ In October 2022, the FHWA NDE Laboratory conducted a workshop on the integration of NDE and structural health monitoring into asset management. The laboratory has published reports on the research on the evaluation of bridge decks with overlays (FHWA-HRT-21-023) and on the

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