<rss version="2.0" xmlns:atom="https://www.w3.org/2005/Atom">
  <channel>
    <title>Transport Research International Documentation (TRID)</title>
    <link>https://trid.trb.org/</link>
    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
    <description></description>
    <language>en-us</language>
    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
    </image>
    <item>
      <title>Assessing Nanomaterial-Modified Marginal Aggregates for Flexible Pavement Construction Using Fuzzy Analytical Hierarchy Process</title>
      <link>https://trid.trb.org/View/2683042</link>
      <description><![CDATA[This study investigates the feasibility of utilizing locally sourced marginal aggregates—broken bricks, shale, river stones, and wooden stones—as alternatives to conventional stone aggregates for subbase layers of flexible pavement. Laboratory evaluations revealed that untreated marginal aggregates had inferior properties compared to conventional aggregates. To improve their performance, a stabilization comprising 3% ordinary portland cement and nanomaterials (Terrasil and Zycobond) was applied. The treated samples showed significant enhancements: the California bearing ratio of river stone mixes increased by 132%, reaching 49.98%; the unconfined compressive strength of broken brick mixes rose by 150%, reaching 3.45 MPa; and the compressive strength improved by 39% for the same mix. Maximum dry density was achieved at a 50:50 soil-to-aggregate ratio for most mixes, except for river stones, which required a 40:60 ratio. The multicriteria decision-making approach, specifically the fuzzy analytical hierarchy process, was used to rank the aggregates based on laboratory test results. Broken bricks emerged as the top-performing material, followed by shale, while river stones and wooden stones ranked lower but remained viable for use after stabilization. These findings support the use of treated marginal aggregates as cost-effective and sustainable alternatives in flexible pavement construction.]]></description>
      <pubDate>Tue, 14 Apr 2026 10:10:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2683042</guid>
    </item>
    <item>
      <title>National Airport Pavement Test Facility Construction Cycle 9 Volume 3—Geosynthetic Test</title>
      <link>https://trid.trb.org/View/2688793</link>
      <description><![CDATA[Construction Cycle 9 (CC9) was the ninth in a series of full-scale airport pavement tests performed at the Federal Aviation Administration (FAA) National Airport Pavement Test Facility, the fifth involving flexible pavements. It contained four test areas: fatigue, geosynthetics, cement-treated permeable base, and overload. This report addresses the geosynthetics test area, which consisted of two test items: LFC-3N with a geotextile separation fabric between the subgrade and subbase plus a Class B geogrid at the subbase/base interface, and LFC-3S with just the geotextile. These test items were subjected to simulated full-scale aircraft trafficking along with a control test item (LFC-4S) with similar materials and thickness but not containing geosynthetics. The goal of this test was to quantify any improvement in performance of the geosynthetic test items when compared to the control test item. Data were collected through laboratory and in situ testing, visual evaluation, and embedded pavement sensors. Researchers analyzed the effect of construction practices on pavement performance and compared pavement responses in all structural layers, in particular examining how the accumulation of permanent deformation is affected by the presence or absence of geogrid reinforcement and geotextile separation fabric. All three test items experienced structural failure before the end of traffic. Test items with geosynthetic elements had greater surface upheaval, rutting, and crack density than the control section; however, this was attributed to improper compaction of the sublayers during construction. The embedded sensors indicated that the geogrid increased the resistance to permanent deformation in the granular subbase layer. Despite accumulating higher surface rutting (attributed to the underlying compaction issues), the geogrid-reinforced test item LFC-3N exhibited lower upheaval than the other test items when trafficked beyond the pass where the failure criterion was met (1-in. dilative heave). The inclusion of geogrid aided in lateral confinement and resulted in lower permanent deformation in the subbase layer of LFC-3N than in the subbase layers of the LFC-3S and LFC-4S.]]></description>
      <pubDate>Mon, 13 Apr 2026 16:48:09 GMT</pubDate>
      <guid>https://trid.trb.org/View/2688793</guid>
    </item>
    <item>
      <title>Evaluating the Drainage Performance of Wicking Geotextile Under Freeze–Thaw Conditions below Pavement Infrastructure</title>
      <link>https://trid.trb.org/View/2683122</link>
      <description><![CDATA[Pavements constructed on frost-susceptible subgrades are often subjected to distress because of cyclic freeze–thaw (F–T) conditions resulting from seasonal temperature variations. Cyclic frost heaving significantly affects the long-term performance of pavements, particularly during the thawing phase, where excess water weakens the subgrade. Numerous solutions have been studied to mitigate these issues, including soil stabilization, soil replacement, and drainage improvements using geosynthetics. Traditionally, many woven and non-woven geotextiles have been used to remove excess water; they are effective at draining water under saturated conditions. However, they are ineffective at removing moisture under unsaturated conditions because they cannot provide sufficient capillary suction. A new type of geotextile—the wicking geotextile—has been introduced, with finer, deeper grooves to generate higher capillary suction, aiding the extraction and transport of excess moisture even in unsaturated conditions. In this paper, a research study was designed to evaluate the performance of the wicking geotextile under cyclic F–T conditions. Large-scale laboratory tests with an unreinforced control section (CS) and a reinforced section (RS) were designed using frost-susceptible soils. The test setup was subjected to two F–T cycles under controlled temperature conditions with freezing temperature set at −18°C (−0.4°F). The results showed the wicking geotextile effectively removed and transported moisture, thereby reducing water content in the RS subbase by 51% and in the subgrade by 7% compared with CS. It also helped redistribute moisture uniformly across the pavement layers and maintained steady drainage even after cyclic F–T, indicating consistent performance under harsh environmental conditions.]]></description>
      <pubDate>Sun, 22 Mar 2026 17:18:11 GMT</pubDate>
      <guid>https://trid.trb.org/View/2683122</guid>
    </item>
    <item>
      <title>Tire Derived Aggregate Embankment Design and Construction for Saskatchewan Highway 39</title>
      <link>https://trid.trb.org/View/2665661</link>
      <description><![CDATA[Saskatchewan recycles all tires, including passenger car and light truck tires, agricultural tires, and semi tires. It is environmentally and socially acceptable to recycle tires, and agencies in North America have been doing so for years. Recycling tires is important because scrap tires take up landfill space, pose a risk of fire when stockpiled incorrectly, hold water when not shredded, and can help conserve natural aggregate resources, depending on the application. Tire Derived Aggregate (TDA) is an engineered material made from shredded tires. TDA has been used in civil engineering applications as lightweight fill to build embankments, roadway ramps, weigh scales, backfill for retaining walls, and to repair frost heaves for over 40 years.  In 2022, the Saskatchewan Ministry of Highways (ministry) constructed the ministry’s first highway embankment with TDA as lightweight fill. A greenfield project site on a new section of Highway 39 near Corinne required a large embankment fill for the southbound lanes and had in-situ soils that would benefit from the frost protection properties that TDA offers. TDA was utilized as lightweight fill in a location where the road embankment section was being built over an existing dugout. The TDA embankment section was 34.0 m by 147.6 m and 1.9 m thick and was constructed with a total of 6,332 cubic metres of TDA. Using a conversion of 100 tires per cubic metre of TDA, approximately 632,000 tires were recycled. A 2.95 m thick clay fill embankment with an additional soil surcharge layer of 0.75 m was placed on top of the TDA layer and allowed to settle prior to further construction. The surcharge load was removed to accommodate the pavement structure, and a flexible asphalt concrete pavement structure was constructed on top of the embankment, and the road was opened to traffic in 2024.  This paper presents the design and construction details for this project, the instrumentation used to monitor the TDA layer, and comments on lessons learned. The TDA embankment layer environmental and geotechnical monitoring is also summarized.]]></description>
      <pubDate>Thu, 12 Mar 2026 08:52:52 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665661</guid>
    </item>
    <item>
      <title>LWD &amp; DCP Testing for Pavement Foundation and Subbase</title>
      <link>https://trid.trb.org/View/2672074</link>
      <description><![CDATA[This research effort was undertaken to establish test methods, limits, and protocols to implement lightweight deflectometer (LWD) and dynamic cone penetrometer (DCP) testing and acceptance criteria for Pennsylvania’s subgrade soil and unbound pavement layers. Historically, density-based criteria have been predominantly used to assess the subgrade/base compaction quality. This study sought to assess the viability of LWD and DCP as tools for quality control/assurance in the compaction of highway subbase and base materials in Pennsylvania. Five different types of soils, covering a wide range of gradations, were selected for the laboratory study. The study included small-scale laboratory testing and progressed to large-scale laboratory testing in a test pit and subsequently field testing. The optimum moisture content was determined in the laboratory for each soil. Laboratory LWD testing was conducted on all soils at different moisture contents and compaction levels. The LWD/DCP research in the test pit and in the field was limited to two of the soils. The general conclusion from this study was that LWD and DCP are useful tools and PennDOT can benefit from including them in its subgrade/base compaction quality control specifications. The lab LWD deflections were significantly lower than those obtained in the field and in the test pit due to the effect of the strong floor, an important finding to consider when developing threshold values. The results of the study were used to develop a set of recommendations for PennDOT toward the use of LWD/DCP for field quality control of compacting subgrade, subbase, and base layers. The recommended threshold values are based on this study and subject to validation and/or adjustment as further information and data become available from LWD/DCP testing in actual field conditions.]]></description>
      <pubDate>Wed, 25 Feb 2026 16:28:05 GMT</pubDate>
      <guid>https://trid.trb.org/View/2672074</guid>
    </item>
    <item>
      <title>Seasonal Weight Restriction Decision Making Based on Understanding and Monitoring of Frost Susceptibility of Pavement Structures</title>
      <link>https://trid.trb.org/View/2671988</link>
      <description><![CDATA[This study aims to critically assess the variation of stiffness, temperature and moisture throughout the base and subbase structure to better determine the capacity of roads as the seasons transition from winter to spring. The objectives of this project are to critically assess the variation of temperature, moisture, stiffness and strength throughout the base and subbase structures during different driving seasons to better determine the capacity of roads from winter to spring to summer driving seasons. And propose an interpretation and analysis protocol of continuously collected data to create a decision-making process for the frozen road declaration, midseason thaw, ending the frozen road declaration, and imposing and ending spring weight restriction in the State of Wisconsin.]]></description>
      <pubDate>Wed, 18 Feb 2026 11:28:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/2671988</guid>
    </item>
    <item>
      <title>Investigating the Effectiveness of Enzymatic Stabilizers for Reclaimed Stabilized Base Projects</title>
      <link>https://trid.trb.org/View/2666678</link>
      <description><![CDATA[Reclaimed stabilized base (RSB) with an appropriate stabilizing agent is an appealing option for many rehabilitation projects. Depending on the type of base layer, various traditional stabilizing agents (e.g. cement, lime, calcium chloride, asphalt emulsion) are used in RSB projects to rehabilitate roadways by reclaiming the base material. Despite their advantages, traditional stabilizers entail some disadvantages (e.g. chemical reactions that might lead to disintegration of bonds). An alternative to the traditional stabilizers is using enzymatic stabilizers or a combination of an enzyme with traditional stabilizers in RSB leading to an improved stabilization outcome. This study investigated the effects of Xanthan Gum (XG) biopolymer on the strength and stiffness of roadway subbase materials as a full or partial replacement of cement. The subbase material was created in the lab and designed to represent the general gradation specified by regional departments of transportation. Scanning electron microscope imagery indicated that the XG coats soil particles and creates connections between them. For specimens treated with only XG, the results indicated an optimal treatment level of 1.0% of the dry mass of the subbase material, resulting in an unconfined compressive strength of about 4,000 kPa for specimens cured for 28 days compared to the untreated specimen with a strength of about 200 kPa. For specimens treated with both XG and cement, the results indicated an optimal level of treatment of 1.0% XG and 1.0% cement by dry mass of the subbase material. This combination demonstrated increased compressive strength of about 1,400 kPa. Combinations of XG and cement also resulted in a desirable ductile post-peak behavior in the treated subbase specimens compared to specimens treated with cement alone, which often produces undesirable brittle behavior]]></description>
      <pubDate>Tue, 10 Feb 2026 09:11:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/2666678</guid>
    </item>
    <item>
      <title>Statistical analysis of test data on unbound aggregate layers at experimental site</title>
      <link>https://trid.trb.org/View/2643545</link>
      <description><![CDATA[The field performance of unbound aggregate layers was investigated using an extensive program of light weight deflectometer (LWD), air permeameter (APT) and nuclear density tests on two testing strips, one on untreated subgrade and the other on cement-treated subgrade, constructed at an experimental site. The main objective was to examine the use of LWD and APT for control of the state of compaction and hydraulic conductivity of aggregate layers commonly used as roadway subbase draining or filter/separation layers. The test strips construction and the testing program are described, and test results are discussed. Statistics and correlation studies of the collected data, as well as Bootstrap resampling simulations are presented and serve as a basis for assessing the testing methods and the influence of statistical sample size on the reliability of QA/QC outputs. The main outcomes address the spatial variability in the measured properties, the evaluation of materials and methods used to construct the strips, and the methods used for characterising the layers. These highlight some limitations in current quality assurance guidelines and suggest a risk-informed approach.]]></description>
      <pubDate>Sun, 01 Feb 2026 16:32:19 GMT</pubDate>
      <guid>https://trid.trb.org/View/2643545</guid>
    </item>
    <item>
      <title>Incorporating Knowledge from Sensor Data and In-Situ Testing into the Design Framework of Geogrid-Stabilized Pavement Aggregate Layers</title>
      <link>https://trid.trb.org/View/2661771</link>
      <description><![CDATA[A stiff mechanically stabilized layer (MSL) is achieved by installing a geogrid in a constructed pavement aggregate base/subbase. The inclusion of geogrid is known to improve pavement performance, yet a direct quantification and integration of geogrid benefits into pavement design has remained underutilized in many state transportation agency practices. This study attempts to address this gap by examining the integration of state-of-the-art sensor data and in-situ testing into the analysis and design of geogrid-stabilized pavement aggregate layers. Using automated plate load testing (APLT) on instrumented pavements with pressure cells and innovative Bender Element (BE) field sensors, a comprehensive paired testing effort was conducted on three pavement test sections constructed as part of the US-20 highway reconstruction project in Elkhart, Indiana. The field experiment included a control section with no geogrid and two geogrid-stabilized sections where a biaxial geogrid was installed in two different depths within the constructed unbound aggregate layers. The in-situ tests aimed to measure the composite resilient modulus and capture the deformation characteristics of the aggregate layers under repeated loading. Results demonstrated that sections stabilized with geogrids exhibited improved structural performance, evidenced by higher resilient moduli and reduced permanent deformation accumulations compared with the control section. Moreover, layer modulus enhancement ratios derived from shear wave velocity measurements with BE sensors indicated that geogrid sections exhibited increased local stiffness characteristics near geogrids. Based on the field study findings, a mechanistic approach was introduced to analyze geogrid-stabilized aggregate base/subbase and adequately incorporate their structural contributions into pavement design procedures.]]></description>
      <pubDate>Thu, 29 Jan 2026 10:06:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/2661771</guid>
    </item>
    <item>
      <title>Thermal behavior of permeable pavements under freeze–thaw conditions</title>
      <link>https://trid.trb.org/View/2635382</link>
      <description><![CDATA[This study develops and validates a one-dimensional (1D) physics-based model for simulating freeze–thaw dynamics in permeable pavements, using field data from a test site in Aalborg, Denmark (2022-2024) that includes continuous temperature measurements at 3, 6, and 30 cm depths and water table observations. The model, adapted from the NOAA framework, incorporates laboratory-measured thermal properties for the engineered pavement layers and uses a custom soil moisture profile to integrate the observed water table data. The calibrated model demonstrated excellent performance, particularly in the permeable subbase layer (30 cm depth), which serves as a rigorous test of the model’s physical realism. At this depth, the model achieved high Nash–Sutcliffe Efficiency (NSE) values of 0.995 for the entire period and 0.990 for the second winter period. Results highlight the critical importance of calibrating global thermal conductivity factors to accurately simulate pavement temperatures, particularly during winter freeze–thaw cycles. Sensitivity analyses confirmed that adjustments to these thermal properties led to substantial improvements in model accuracy in the overlying permeable subbase. While variations in subgrade porosity had minimal impact at shallow depths, they significantly influenced thermal behavior in the subbase. Accurate thermal dynamics predictions are critical for assessing freeze–thaw induced damage mechanisms such as frost heave and thaw settlement, which impact pavement durability. Future research should build upon this thermal foundation by integrating more complex moisture and ice content models to enable physical damage prediction. The developed approach represents an important step towards supporting the long-term resilience of permeable pavement systems in cold climates.]]></description>
      <pubDate>Thu, 29 Jan 2026 08:52:38 GMT</pubDate>
      <guid>https://trid.trb.org/View/2635382</guid>
    </item>
    <item>
      <title>Evaluation of the performance of a geogrid placed in a cement-treated subbase using accelerated pavement testing</title>
      <link>https://trid.trb.org/View/2643732</link>
      <description><![CDATA[Road construction costs are high partly due to the scarcity and cost of good quality building materials. The inclusion of geosynthetics in flexible pavement structures has been shown to improve pavement performance. The study indicated the potential benefit of increasing the life of the pavement by adding a multi-shape geogrid layer to a cement-treated subbase. APT testing was conducted using the Heavy Vehicle Simulator (HVS) of the Council for Scientific and Industrial Research (CSIR) in South Africa. When the rutting data, deflection data and the stiffnesses back-calculated from FWD data are considered, it is evident that the inclusion of the geogrid into the cement-treated layer was beneficial and could increase the life of the pavement significantly. The addition of the geogrid to the structure led to an approximate 5% increase in the construction cost. This is negligible in comparison to the significant increase in pavement life. However, the results are valid for a relatively strong (10–30 million ESAL) design. Further work should include the use of the geogrid in a cement-treated base in a weaker pavement where the benefit could potentially be higher.]]></description>
      <pubDate>Mon, 26 Jan 2026 08:41:43 GMT</pubDate>
      <guid>https://trid.trb.org/View/2643732</guid>
    </item>
    <item>
      <title>An Integrated Design Approach for Stabilized Soil Subbase to Prevent Macroscopic Fatigue Cracking</title>
      <link>https://trid.trb.org/View/2630949</link>
      <description><![CDATA[Stabilized soil is widely utilized in pavement engineering to address the disposal of engineering muck, but its fatigue resistance remains a significant challenge. In this study, an integrated design approach for stabilized soil subbases was proposed to prevent macroscopic fatigue cracking and achieve long-lasting, high-toughness pavements. First, a dual-parameter failure criterion was established based on damage density and J-integral thresholds derived from fatigue failure points, informed by indirect tensile fatigue tests on multiple stabilized soil materials. Finite element analysis was subsequently applied, utilizing damage evolution modeling, to quantify and predict the progression of damage within the pavement subbase structure. To overcome computational limitations in high-cycle loading analyses, a hybrid approach was implemented, integrating model simplification and damage density master curves. Finally, simulated damage indicators were compared against the predefined failure criteria. Through iterative adjustments to material damage model parameters and structural layer thickness, damage predictions were constrained within the threshold for preventing macroscopic fatigue cracks. According to the COMSOL simulation results, as the thickness of the stabilized soil subbase decreased, both the tensile stress at the critical location at the bottom of the base and subbase layers increased, and damage followed a similar trend. This systematic methodology integrates the fatigue properties of stabilized soil materials and the fatigue behavior of the structure with stabilized subbase, providing a theoretical foundation and technical guidance for their engineering applications in pavement infrastructure.]]></description>
      <pubDate>Tue, 20 Jan 2026 09:09:10 GMT</pubDate>
      <guid>https://trid.trb.org/View/2630949</guid>
    </item>
    <item>
      <title>Real-time monitoring of the degree of compaction of subgrade soil using LWD testing</title>
      <link>https://trid.trb.org/View/2643634</link>
      <description><![CDATA[Developing nations continue to rely on density-based quality control (QC) method for unbound road layers despite the availability of reliable elastic modulus–based approaches. This study evaluates the performance of light weight deflectometers (LWD) as a QC tool for subgrade assessment. Field experiments were conducted on a 1-km under-construction stretch in Bihar, India, to establish target elastic modulus value and compare them with its laboratory results. The mean target elastic modulus obtained in the field and in the laboratory was 43 MPa. Degrees of compaction (DoC) based on elastic modulus were also determined using a novel LWD-based approach. Correlation analysis showed a strong relationship (R² = 0.96) between dry-density DoC and LWD DoC. The requisite elastic modulus corresponding to 97% dry-density DoC was 41 MPa, while the DoC based on elastic modulus for the same modulus value was 95%. The percentage difference between the mean target and assessed elastic modulus values on the subgrade was 2.6%. The influence of in-situ density and moisture content on elastic modulus was further examined, yielding a high R² value of 0.94. Overall, the findings demonstrate that LWD-based elastic modulus evaluation provides an effective non-destructive testing method for subgrade QC in road construction.]]></description>
      <pubDate>Thu, 15 Jan 2026 14:31:04 GMT</pubDate>
      <guid>https://trid.trb.org/View/2643634</guid>
    </item>
    <item>
      <title>3D concrete-printed geocell for reinforcing unbound granular pavement layers</title>
      <link>https://trid.trb.org/View/2643627</link>
      <description><![CDATA[Extensive research is being conducted in 3D concrete printing (3DcP) for automating building construction. However, only a limited number of studies have investigated the possibility of using it to automate pavement construction. This study proposes an innovative method to create geocells with varying shapes along the vertical direction using 3D printing, which is not possible with the currently available geocell technology. This study evaluates the feasibility of using aggregate-bed 3DcP for selectively binding aggregates in unbound granular pavement layers to provide geocell-type confinement. The performance of the 3DcP geocell confined section was compared with the commonly used plastic geocell confined and unconfined pavement sections using laboratory-scale plate load test results. Further, the mechanical properties of the aggregate-bed 3DcP specimens were determined to assess its structural capacity. The interlayer bond strength showed that a 3DcP concrete geocell cannot achieve the same strength properties as a mold-cast concrete geocell. However, the 3DcP geocell provided the strongest confinement effect at relatively low strain levels, while the plastic geocell performed better at higher strain/pressure levels. Overall, 3DcP geocell confinement improved the ultimate bearing capacity of the subbase layer by 50% compared to the unconfined pavement section.]]></description>
      <pubDate>Thu, 15 Jan 2026 14:31:04 GMT</pubDate>
      <guid>https://trid.trb.org/View/2643627</guid>
    </item>
    <item>
      <title>Permanent deformation of unbound granular materials: A review</title>
      <link>https://trid.trb.org/View/2609337</link>
      <description><![CDATA[Several studies have been conducted in the pavement area to try to understand the elastoplastic behavior of unbound granular materials (UGMs) under cyclic loading. This paper presents a literature review on the permanent deformation phenomenon of UGMs when they form granular layers in flexible pavement structures. The factors affecting the resistance to permanent deformation are presented and described, and the evolution of the mathematical equations most used to predict the deformation in these materials under cyclic loading is shown. Conclusions and recommendations for future studies are presented at the end of the manuscript. Despite the substantial number of researches carried out on the subject, the elastoplastic behavior of UGMs has not yet been fully understood. These heterogeneous and anisotropic materials change their behavior mainly with stress magnitude and water content, but they are also strongly dependent on the way factors such as gradation, density, porosity, morphology, chemical and mineralogical composition, temperature, among others, interact. Generally, most of the mathematical equations that try to predict the accumulation of permanent deformation in UGMs are empirical, based on Repeated Load Triaxial (RLT) tests, they cannot simulate the three components of cyclic stress to which a UGM is subjected in a pavement, their parameters are difficult to determine experimentally and do not show physical meaning (they are obtained by regression). In recent years, studies to evaluate the use of recycled aggregates and the effect of temperature (mainly at low temperatures) have increased. Likewise, the use of various technological tools such as artificial neural network (ANN) modeling, and so forth, has increased.]]></description>
      <pubDate>Fri, 05 Dec 2025 14:08:32 GMT</pubDate>
      <guid>https://trid.trb.org/View/2609337</guid>
    </item>
  </channel>
</rss>