<?xml version="1.0" encoding="utf-8"?><rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom"><channel><title>TRB Publications Index</title><link>http://pubsindex.trb.org/</link><atom:link href="http://pubsindex.trb.org/common/TRIS Suite/feeds/rss.aspx?tc=NN%3AGu%2A" rel="self" type="application/rss+xml" /><description></description><language>en-us</language><copyright>Copyright © 2015. 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>TRB Publications Index</title><url>http://pubsindex.trb.org/Images/PageHeader-wTitle.png</url><link>http://pubsindex.trb.org/</link></image><item><title>Evaluation of Critical Pavement Responses from Accelerated Pavement Testing on Airfield Flexible Pavements Surfaced with Hot and Warm Mix Asphalt</title><link>http://pubsindex.trb.org/view/2709231</link><description><![CDATA[Highway agencies frequently use warm mix additives as compaction aids. Lower production temperature of the warm mixes simultaneously entails the benefit of widening the paving window. Airport authorities can ensure significant fiscal savings with reduced downtime through the adoption of similar technologies in airfield paving. However, limited scientific information exists concerning the performance of these materials in airside flexible pavements. Aircraft gross weights and tire pressures have also been routinely increasing over the last few decades with the advent of new-generation aircraft. The Federal Aviation Administration (FAA) procured a sixth-generation heavy vehicle simulator, airfields (HVS-A) to investigate the performances of resilient pavement materials under simulated aircraft loading. Accordingly, six full-scale test lanes were constructed during Test Cycle 1 (TC1) at FAA’s National Airport Pavement and Materials Research Center (NAPMRC) using four different asphalt concrete (AC) mixes with two different binder grades. Each test lane was divided into three test sections. Asphalt strain gauges and pressure cells were installed in the test sections to monitor the critical pavement responses over the duration of traffic tests. Corresponding test sections were trafficked under different combinations of high tire pressure and temperature. This paper examines the tensile strains at the bottom of AC and compressive stresses on top of the subgrade in reference to the observed rutting performances in four TC1 outdoor test lanes. The respective hot and warm mixes exhibited comparable rutting performances, and the sensor observations corroborated the related findings.]]></description><pubDate>Mon, 01 Jun 2026 16:52:46 GMT</pubDate><guid>http://pubsindex.trb.org/view/2709231</guid></item><item><title>Vertical Bearing Characteristic of Precast Hybrid Reinforcement Concrete Pipe Pile Considering Different End Forms in Stiff Silty Clays</title><link>http://pubsindex.trb.org/view/2701106</link><description><![CDATA[Precast prestressed reinforced concrete (PRC) pipe piles are increasingly adopted where static pressing is impractical; however, design-oriented evidence for their vertical bearing behavior in stiff silty clays remains limited. This study combines site static cone penetration tests with full-scale static load tests on hammer-driven PRC pipe piles with open-ended and closed-ended tips to clarify the governing load transfer mechanism and to improve capacity prediction for engineering design. The results show that pile tip configuration was a key factor influencing the bearing behavior of PRC pipe piles. Open-ended piles experience stronger driving-induced disturbance in the tested stiff clay layers, leading to lower mobilized shaft resistance than closed-ended piles. The responses of both pile types can be well described by a bilinear strain hardening load transfer relationship. Building on these observations, a three-stage load transfer function based on Rusch elastoplastic theory was developed and calibrated using test data, achieving improved ultimate bearing capacity prediction compared with conventional design parameter selection. For designs in stiff silty clay, median values of shaft resistance are recommended for open-ended piles; however, the upper-bound values of shaft and base resistances can be adopted for closed-ended piles. These recommendations should be applied cautiously beyond the tested pile configurations, soil properties, and installation method.]]></description><pubDate>Mon, 11 May 2026 14:37:18 GMT</pubDate><guid>http://pubsindex.trb.org/view/2701106</guid></item><item><title>Decision Framework for Concrete Pavement Maintenance Based on Falling Weight Deflectometer and International Roughness Index Data</title><link>http://pubsindex.trb.org/view/2659375</link><description><![CDATA[A reliable decision model in pavement management systems (PMS) is important to maintain the quality and serviceability of pavement systems in the face of increasing traffic volumes and more severe climate conditions. Even though accurate pavement condition assessment is essential for a decision model, there are limited approaches to practically evaluate the structural condition of concrete slabs and the functional condition of concrete pavements. Thus, this study identified practical methods to estimate the remaining service life (RSL) for pavement condition evaluation and developed a decision framework to recommend more appropriate maintenance strategies for concrete pavements. The stress-to-strength ratio (SSR) derived from falling weight deflectometer (FWD) deflection data was selected to estimate RSL based on the structural capacity of concrete slabs. The international roughness index (IRI) was used to estimate RSL based on functional conditions, and a new IRI prediction model was developed for concrete pavements. These structural and functional condition-based RSLs were integrated into the proposed decision framework to provide a more reliable basis for maintenance decisions. Since the proposed framework requires only FWD and IRI data, the most common non-destructive test data sets, it can be practically incorporated into current PMS practices. Furthermore, the RSL calculation equations can be easily calibrated for local conditions, and SSR and IRI threshold values can be adjusted to meet agency needs. This flexibility allows the proposed framework to be implemented by other agencies or in different countries. Therefore, the proposed decision framework can potentially improve current PMS practices, leading to better quality of concrete pavements.]]></description><pubDate>Tue, 27 Jan 2026 17:08:28 GMT</pubDate><guid>http://pubsindex.trb.org/view/2659375</guid></item><item><title>A Real-Time Degeneracy Sensing and Compensation Method for Enhanced LiDAR SLAM</title><link>http://pubsindex.trb.org/view/2553288</link><description><![CDATA[LiDAR is widely used in Simultaneous Localization and Mapping (SLAM) and autonomous driving. The LiDAR odometry is of great importance in multi-sensor fusion. However, in some unstructured environments, the point cloud registration cannot constrain the poses of the LiDAR due to its sparse geometric features, which leads to the degeneracy of multi-sensor fusion accuracy. To address this problem, we propose a novel real-time approach to sense and compensate for the degeneracy of LiDAR. Firstly, this paper introduces the degeneracy factor with clear meaning, which can measure the degeneracy of LiDAR. Then, the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) clustering method adaptively perceives the degeneracy with better environmental generalization. Finally, the degeneracy perception results are utilized to fuse LiDAR and IMU, thus effectively resisting degeneracy effects. Experiments on our dataset show the method’s high accuracy and robustness and validate our algorithm’s adaptability to different environments and LiDAR scanning modalities.]]></description><pubDate>Mon, 26 Jan 2026 14:17:10 GMT</pubDate><guid>http://pubsindex.trb.org/view/2553288</guid></item><item><title>Monitoring Method and System of Pre-Convergence Deformation of Soft Surrounding Rock Tunnel</title><link>http://pubsindex.trb.org/view/2633027</link><description><![CDATA[The prediction and early warning of tunnel collapse in weak surrounding rock is very important for tunnel construction safety, but the current monitoring methods are insufficient. In view of the shortcomings of existing monitoring methods for deformation of advanced core soil, a monitoring method of pre-convergence deformation of advanced core soil in front of the tunnel face was proposed; this involves placing an array displacement meter (ADME) in a leading small conduit and monitoring the deformation of the leading small conduit. The coupling accuracy test data of the ADME and steel pipe were combined to prove the feasibility of the device and test method. Finally, it is proposed to place the ADME in the lead duct, calculate the displacement of the measuring unit through the change of gravity and angle, and obtain the pre-convergence deformation of the lead core soil in front of the palm face. The results show that the floating error of the measuring unit of the ADME is 0.2 mm by calibrating the precision measuring device designed by itself. The absolute error is 0.2 mm @ 1 m. When the ADME is used for deformation measurement with displacement greater than 2 mm @ 1 m, the relative error can be controlled within 10%. Through the above deformation monitoring system, it is expected to realize a real-time monitoring method which can ensure monitoring accuracy and frequency, reduce interference to tunnel construction, and improve the safety and accuracy of tunnel construction in weak surrounding rock.]]></description><pubDate>Wed, 03 Dec 2025 10:27:28 GMT</pubDate><guid>http://pubsindex.trb.org/view/2633027</guid></item><item><title>Evaluating the Use of Traffic-Speed-Deflectometer-Based Pavement Structural Data in Virginia Department of Transportation’s Pavement Management Processes for Flexible Pavements</title><link>http://pubsindex.trb.org/view/2630588</link><description><![CDATA[Incorporating the structural condition of pavements into the maintenance and rehabilitation treatment selection process is essential for improving performance and prolonging service life. However, because of challenges in network-level structural condition testing, agencies often rely solely on surface-based condition data. This paper proposes and evaluates an approach to incorporate structural condition information from a traffic speed deflectometer into the pavement management decisions of the Virginia Department of Transportation in the U.S. The approach follows the AASHTO design procedure to calculate the effective structural number (SNeff) and uses SNeff to determine the remaining structural life (RSTL). Analysis of 4,250?lane-miles of interstate and primary roads revealed that, while 90%, 80%, and 30% of primary roads had an RSTL of at least 5, 10, and 20?years, respectively, interstate roads were in better condition, with 91%, 88%, and 82% having an RSTL of at least 5, 10, and 20?years, respectively. A structural condition indicator based on RSTL thresholds for selecting treatment categories was proposed. Final treatment recommendations were derived by combining the current surface-distress-based categories with the proposed structural-condition-based categories. Unconstrained needs analysis, including detailed case studies, showed differences in needs when structural condition was considered, compared with using only surface-based condition information. These differences in needs varied with the existing pavement condition. While the proposed RSTL approach can enhance treatment selection, a systematic investigation is recommended to determine appropriate intervals between structural testing cycles at the network level.]]></description><pubDate>Tue, 25 Nov 2025 16:56:37 GMT</pubDate><guid>http://pubsindex.trb.org/view/2630588</guid></item><item><title>Application of Falling Weight Deflectometer in Railway Track to Assess Ballast and Subgrade Conditions</title><link>http://pubsindex.trb.org/view/2616839</link><description><![CDATA[This paper describes an investigation into the applicability of falling weight deflectometer (FWD) for evaluating structural conditions of railroad track substructures. The research study involved six full-scale test sections constructed at the U.S. Army Engineering Research and Development Center facility, each with different combinations of fouled and clean ballast, as well as poor, moderate, and good subgrade conditions. The experimental program focused on investigating the impact of different FWD load plate materials—aluminum, plastic, and rubber, in addition to the original steel—on the measurement repeatability and condition assessment of ballast and subgrade using both centerline and offset geophone sensors. The FWD test results collected from the different substructure conditions were analyzed using statistical methods, including F-tests, T-tests, and analysis of variance, to determine significance of results and any differences in deflections. Results show that the type of loading plate affects primarily the centerline deflection and measurement repeatability. Furthermore, the measured centerline deflections could be used to distinguish between fouled and clean ballast conditions with good subgrades, while the 40?in. (101.6?cm) offset sensor deflection could determine poor, moderate, and good subgrades, regardless of ballast conditions. This research demonstrates the potential of using the FWD as an effective and reliable tool for track substructure assessment in ballasted track and provides insights into the effects of ballast fouling and subgrade quality on track performance.]]></description><pubDate>Sat, 01 Nov 2025 18:26:25 GMT</pubDate><guid>http://pubsindex.trb.org/view/2616839</guid></item><item><title>Inversion of Asphalt Pavement Properties From Slopes Reported by the Traffic Speed Deflectometer</title><link>http://pubsindex.trb.org/view/2607912</link><description><![CDATA[The traffic speed deflectometer (TSD) is a semi-trailer truck equipped with Doppler lasers. The device attempts to measure ride-surface slopes at several distinct locations caused by its own loading while moving at highway speeds. This study investigated the potential of the TSD to deliver a project-level evaluation of asphalt pavement infrastructure. A twofold objective was defined: (i) outlining a procedure for inverting TSD-reported slopes and obtaining the mechanical properties of individual pavement layers, and (ii) demonstrating the procedure by application to a real, field-measured dataset. In general, the inversion procedure was based on matching model-calculated slopes to TSD-reported slopes while accounting for the movement of the entire TSD truck and without assuming that the slope is zero at a certain offset distance from the rear axle. The procedure utilized a layered viscoelastic half-space model capable of dealing with moving loads. Accordingly, the sought properties for inversion were the viscoelastic creep compliance master curve of the asphalt layer and the elastic moduli of all other layers. Application of the procedure to a field dataset revealed that the coefficient of variation of the inverted moduli had an increasing trend with depth (in absolute terms), indicating that the property inference of deeper layers from TSD-reported slopes has lower reliability compared with the property inference of shallow pavement layers.]]></description><pubDate>Thu, 09 Oct 2025 11:01:48 GMT</pubDate><guid>http://pubsindex.trb.org/view/2607912</guid></item><item><title>Evaluating Driver Response to a Speed Feedback Trailer at Median Crossovers Within Freeway Construction Work Zones</title><link>http://pubsindex.trb.org/view/2606611</link><description><![CDATA[A series of field evaluations were performed to assess the speed reduction effects of a speed feedback trailer (SFT) positioned at various locations before and after a median crossover section within a freeway construction work zone. The SFT was evaluated at three positions at the lane closure taper approaching the median crossover: 1) taper start, 2) taper end, and 3) 800 ft beyond the taper end near the initial R2-1a “Where Workers Present 45” speed limit sign. The SFT was also evaluated within the barrier-divided two-way traffic section after the traffic had crossed over the median. Vehicle speeds approaching the SFT were measured at several locations using LiDAR guns. Positioning the SFT slightly beyond the end of a lane closure taper, adjacent to the nearest R2-1a sign resulted in speed reductions that were both greater in magnitude and sustained further into the work zone compared with when the SFT was located at the taper start or taper end. With the SFT in this position, speeds near the start of the median crossover, which was more than half a mile beyond the SFT and nearly a mile beyond the start of the taper, were 1.4 mph lower compared with when no SFT was present. The SFT was similarly effective for reducing speeds of passenger cars when positioned within the crossover section, although heavy truck speeds were unaffected.]]></description><pubDate>Mon, 06 Oct 2025 14:29:17 GMT</pubDate><guid>http://pubsindex.trb.org/view/2606611</guid></item><item><title>Introducing a New Solution for Network Level Pavement Structural Evaluation Using Traffic Speed Deflectometer Device (TSDD): A Case Study of Mississippi Department of Transportation</title><link>http://pubsindex.trb.org/view/2601560</link><description><![CDATA[This paper introduces a new approach to evaluate the structural performance of road networks using data collected by a traffic speed deflectometer device (TSDD). The advantage of this platform over traditional backcalculation methods is that thickness information for the pavement structure is not required. This is important for network-level evaluations as the information about layer thicknesses is rarely available for agencies. The platform proposed in this study determines the effective structural number (SNeff) with inputs readily available from testing. In this study, a database containing 20,000 randomly generated deflection basins was simulated, and the SNeff for each simulation was calculated. The simulated data were then used as input to train a deep learning model. The trained model on the synthetic database showed an R2 of 0.97 on both the test and training sets showing its robustness. The model was then validated with 12.7?mi on a major highway in Mississippi. The determined SNeff values were then compared with those of the American Association of State Highway and Transportation Officials (AASHTO) 1993 model as well as those obtained from backcalculation. The results indicate that the proposed model can accurately measure SNeff, with the notable advantage of not requiring thickness as an input. This finding is a big step forward in processing TSDD results at large scale. Following the initial analysis, the model was used to process additional TSDD data collected by MDOT. The time to process 1.5?million MDOT records was less than 5.2?s, which shows the tremendous promise of the proposed platform as a useful tool for real time structural evaluation of the roads.]]></description><pubDate>Mon, 22 Sep 2025 16:10:35 GMT</pubDate><guid>http://pubsindex.trb.org/view/2601560</guid></item><item><title>Evaluation of a Low-Activity Nuclear Density Gauge for Acceptance Testing of Asphalt Pavements for Percent-Within-Limit and Averaging Specifications</title><link>http://pubsindex.trb.org/view/2582347</link><description><![CDATA[Compaction of asphalt concrete (AC) to a specific density is required to achieve the designed engineering properties and performance characteristics of a pavement layer. The finished AC layers do not exhibit uniform density because of variability in production and construction processes. Nuclear density gauges (NDG) are used for density acceptance testing because of their favorable measurement properties, that is, sensitivity, precision, depth of measurement or investigation, and accuracy. This study evaluated a recently developed direct transmission-mode-based method for low-activity nuclear density gauges (LNDG-TM), which notably, are exempt from US nuclear regulatory restrictions. The measurement precision of the LNDG-TM method was determined from a six gauge–operator pair inter-laboratory study. The repeatability and reproducibility standard deviations were 0.7 lb/ft3 (11 kg/m3) and 1.0 lb/ft3 (16 kg/m3), respectively. The materials and construction density variability (dMC) for an interstate surface course were determined by analyzing control-strip density data. The dMC at the 95% confidence level, as determined with the core extraction (CE) method, was 2.3 lb/ft3 (37 kg/m3), whereas those determined with two NDGs were 3.0 lb/ft3 (48 kg/m3) and 2.2 lb/ft3 (35 kg/m3), respectively. The LNDG-TM method was evaluated for acceptance testing, wherein the provided density specifications were the percent-within-limit (PWL) and averaging. Two surface courses were tested: one with the PWL specification wherein the CE method was the agency-approved method, and the other with the averaging specification, wherein the agency-approved method was the thin-lift NDG method. For both projects, results from using the LNDG-TM method agreed well with those obtained using the agency-approved methods. Thus, the LNDG-TM method is suitable for density acceptance testing of asphalt pavements.]]></description><pubDate>Tue, 29 Jul 2025 13:55:14 GMT</pubDate><guid>http://pubsindex.trb.org/view/2582347</guid></item><item><title>Long-Term Performance Evaluation of Recycled Concrete Aggregate as a Base Material in Flexible Pavements</title><link>http://pubsindex.trb.org/view/2582345</link><description><![CDATA[This study, conducted by the Florida Department of Transportation (DOT), evaluated the long-term performance of recycled concrete aggregate (RCA) as a base material in flexible pavements compared with standard lime rock (LRK). Field monitoring was carried out at a test site on SR 43/US-301, where both RCA and LRK were used as base materials. Key performance indicators such as falling weight deflectometer (FWD) deflection, cracking, rutting, smoothness, and ride quality were evaluated over time. The findings revealed that RCA outperformed LRK in structural integrity, deflection, rutting resistance, smoothness, and ride quality. These results have significant practical implications, highlighting the importance of comprehensive field evaluations and supporting the viability of RCA as a sustainable alternative in pavement base layer applications. Additionally, the study incorporates local calibration of the Mechanistic-Empirical Pavement Design Guide (MEPDG) to enhance the accuracy of performance predictions specific to RCA behavior in Florida’s environmental conditions. The study demonstrates RCA’s long-term durability and structural benefits in a real-world context.]]></description><pubDate>Tue, 29 Jul 2025 13:55:14 GMT</pubDate><guid>http://pubsindex.trb.org/view/2582345</guid></item><item><title>Stiffness-Based Field-Testing Framework for Design and Evaluation of Pavement Subsurface Layers</title><link>http://pubsindex.trb.org/view/2577190</link><description><![CDATA[Pavement subsurface layers are designed based on the modulus of the subgrade reaction, resilient modulus, or through the California bearing ratio test; yet, the standard method for assessing the condition of as-built soil layers during construction is the nuclear density gauge (NDG) method. The NDG method, however, does not indicate the performance of the pavement sublayers (i.e., strength, stiffness, or modulus) like the parameters used during the design process. This paper discusses the use of the lightweight deflectometer (LWD) and dynamic cone penetrometer (DCP) tests under a proposed stiffness-based field test framework for the construction and evaluation of pavement subsurface layers. Large-scale test sections were built with locally available geomaterials and evaluated with the NDG, LWD, and DCP tests during and after construction. While the results from the NDG tests showed some variability, the LWD test results were more consistent among layers composed of the same material. A correlation was observed between the DCP penetration index and the LWD test parameters (i.e., deflection, dynamic modulus, and impulse stiffness modulus), both unbiased measures of soil stiffness. From this study, the implementation of both devices can provide near-surface layer measurements with the LWD test and post-construction evaluation results with the DCP test that can interchangeably provide the user with a more mechanistic-related condition of the pavement subsurface geolayers.]]></description><pubDate>Tue, 22 Jul 2025 10:31:00 GMT</pubDate><guid>http://pubsindex.trb.org/view/2577190</guid></item><item><title>Decision Framework to Determine the Maintenance Strategy Based on Both Structural and Functional Conditions of Asphalt Pavements</title><link>http://pubsindex.trb.org/view/2572989</link><description><![CDATA[A decision model is one of the most important components in pavement management systems (PMS) to determine appropriate maintenance strategies, ensuring desirable conditions of in-service pavements within the given time and budget. However, most decision models focus solely on either functional or structural conditions, despite the importance of considering both concurrently. This study developed a decision framework for determining a more appropriate maintenance strategy for asphalt pavements based on both structural and functional conditions. Three types of structural indicators, calculated from the falling weight deflectometer (FWD) deflections, were used for evaluating pavement structural capacity, while the international roughness index (IRI) measurement was used to assess functional conditions. The selected structural indicators, the structural number ratio, deflection basin parameters, and critical strains, allowed for the assessment of specific pavement layer structural conditions. This leads to the application of a stepwise approach to the decision framework, providing a more accurate maintenance strategy. In addition, user-friendly software was developed to analyze raw FWD and IRI data for a more practical implementation of the proposed decision framework. Since the developed decision framework employs common nondestructive test data, FWD deflection and IRI data, routinely collected by most agencies, it can be easily incorporated into current PMS practices. Furthermore, the use of common nondestructive test data is beneficial for local calibration of thresholds using historical PMS data, allowing the proposed decision framework to be easily implemented in various states or countries.]]></description><pubDate>Fri, 11 Jul 2025 08:39:01 GMT</pubDate><guid>http://pubsindex.trb.org/view/2572989</guid></item><item><title>Characterizing Mechanical Responses of Composite Pavements in Falling Weight Deflectometer Testing for Structural Condition Evaluation</title><link>http://pubsindex.trb.org/view/2572386</link><description><![CDATA[Evaluating the structural condition of composite pavements (i.e., flexible over rigid) is crucial for pavement management systems, which are significantly affected by mechanical responses in the joints of Portland cement concrete (PCC) slabs. However, limited research is concentrated on the effects of PCC joints on the composite pavement mechanical responses in falling weight deflectometer (FWD) testing. In this study, the aim is to develop a practical method for evaluating the structural condition of composite pavements using FWD testing. The proposed method utilizes deflection basin parameters (DBPs) to identify the position of a PCC slab joint and estimate the depth of reflective cracking. The mechanical responses in FWD testing were characterized using finite-element models, and correlations between the DBPs and critical mechanical responses were analyzed. The results were verified using field data sets collected from routine surveys in Indiana. The research indicates that the mechanical responses at the bottom of the asphalt layer present the second fluctuation (SF) caused by the PCC joint in FWD testing. The extreme values of normal and shear strain in the SF can be used as critical mechanical responses to identify the PCC joint and evaluate reflective cracking. When the reflective cracking depth reaches 75% of the asphalt layer thickness, the shear strain increases sharply. The adjusted base damage index and surface curvature index are correlated with the extreme values of normal and shear strains, respectively. This correlation enables recognition of PCC joints and estimation of reflective cracking in composite pavement based on FWD testing.]]></description><pubDate>Fri, 11 Jul 2025 08:39:01 GMT</pubDate><guid>http://pubsindex.trb.org/view/2572386</guid></item></channel></rss>