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    <title>Transport Research International Documentation (TRID)</title>
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    <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>
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      <title>Transport Research International Documentation (TRID)</title>
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      <title>Multi-Source Comprehensive Program to Assess, Monitor, and Report Retroreflectivity of Pavement Markings</title>
      <link>https://trid.trb.org/View/2736591</link>
      <description><![CDATA[This research investigates the feasibility of estimating retroreflectivity of durable longitudinal pavement markings using multi-source data to reduce UDOT's reliance on costly specialized field inspections. The study uses a combination of existing datasets, mobile LiDAR point clouds, street-level roadway imagery, and historical retroreflectivity measurements to develop robust predictive models for assessing pavement marking condition. The research uses existing field retroreflectivity data across major Utah roadways, including I-15, I-80, I- 84, and I-215. The study corridors are dominated by durable pavement markings, so the model development and validation presented in this report primarily reflect the performance of durable marking materials. LiDAR data provided geometry and intensity of light reflected back to the sensing unit, while roadway images were processed to extract visual features and assess the condition of lane markings. Both data streams (i.e., LiDAR and imagery) were analyzed independently and also in combination using machine learning methods, including Random Forest classifiers and convolutional neural networks (CNNs). A fusion model was developed to integrate LiDAR and image-based features for enhanced performance. Results demonstrated that image- and LiDAR-only models can accurately classify pavement markings as compliant or non-compliant with federal minimum retroreflectivity standards. The fusion model outperformed individual models, achieving over 95% accuracy and strong agreement with ground truth data at both segment and corridor levels. Regression models were also developed to predict continuous retroreflectivity values directly from image features. The methods developed in this research were implemented in a portable, user-friendly computer tool that enables UDOT to estimate and monitor pavement marking retroreflectivity via data fusion, LiDAR-only, or image-only models. This approach enhances operational efficiency, supports monitoring for federal compliance, and provides a scalable framework for statewide deployment. This study builds on a previous UDOT research phase that evaluated LiDAR‐only retroreflectivity estimation and extends that work by incorporating street‐level imagery and multi‐source data fusion.]]></description>
      <pubDate>Wed, 05 Aug 2026 09:14:01 GMT</pubDate>
      <guid>https://trid.trb.org/View/2736591</guid>
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    <item>
      <title>Evaluation of Wind-Driven Retroreflective Taxiway Edge Markers</title>
      <link>https://trid.trb.org/View/2730836</link>
      <description><![CDATA[An innovative taxiway edge retroreflective marker, designed to rotate when there is sufficient wind, was evaluated to determine whether the markers would provide adequate visual guidance at night while rotating and when stationary, and whether the innovative rotating feature adds to or detracts from the guidance value. The evaluation was not intended to determine whether the device will or will not meet Federal Aviation Administration (FAA) Specifications. The markers consist of a plastic can or cylinder, 6 1/4 inches by 8 inches tall, mounted on plastic Polyvinyl Chloride (PVC) pipe. Wind collector vanes on the cylinder are used to rotate the cylinder when winds are above approximately 8 knots. Light is reflected at night from retroreflective bands of yellow and blue material and from glass beads embedded in the painted material. The retroreflective bands of material are staggered vertically producing motion or movement both when rotating horizontally and vertically. The test results concluded that the wind-driven edge markers adequately define the taxiway and provided adequate visual guidance for taxiing while the markers were stationary and when rotating during daylight hours and at night. There was not discernible advantage to the rotation feature. The rotation of the device did not significantly enhance guidance and some pilots felt it was distracting.]]></description>
      <pubDate>Sun, 02 Aug 2026 17:23:36 GMT</pubDate>
      <guid>https://trid.trb.org/View/2730836</guid>
    </item>
    <item>
      <title>Techniques Implemented by Road Signal Analysis at National Level</title>
      <link>https://trid.trb.org/View/2686192</link>
      <description><![CDATA[Road markings and traffic signs are integral components of road infrastructure and represent essential road safety elements. Their presence can either positively or negatively influence road users, thereby increasing or decreasing overall road safety, depending on their condition. Road markings and signs play a particularly important role in conditions of reduced visibility. In order for road markings and traffic signs to be visible in such conditions, they must be retroreflective. Retroreflection is the ability of an object to reflect light back towards a light source along the same axis from which it originates [1]. Therefore, in order to ensure adequate levels of reflectivity, both road markings and traffic signs should be checked periodically with metrologically certified measuring instruments. The aim of this paper is to highlight the methods used to analyse the variation in quality parameters on retroreflective films applied to the front of road signs by measuring the retroreflection coefficient RA. For longitudinal road markings, the parameter used to determine their quality is the retroreflected luminance coefficient RL, which is determined continuously. In this study, we looked at how the results were affected by weather and traffic conditions on road signs.]]></description>
      <pubDate>Fri, 31 Jul 2026 09:23:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/2686192</guid>
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    <item>
      <title>Development and Validation of a Methodology to Estimate Retroreflectivity of Pavement Markings Using LiDAR</title>
      <link>https://trid.trb.org/View/2732496</link>
      <description><![CDATA[Longitudinal pavement markings significantly affect traffic safety, particularly in adverse weather and nighttime conditions when crashes and fatalities are often overrepresented. Given the wide range of factors affecting the performance of pavement markings, periodic monitoring is needed to ensure their integrity and adequate retroreflectivity levels. Typical monitoring methods include individual readings from manual retroreflectometers and mobile setups where much larger segments can be covered in shorter periods. However, mobile setups require specialized equipment, calibration, and significant economic resources. This research uses LiDAR data collected as part of asset management efforts to help assess durable pavement markings, primarily longitudinal freeway lines. This project developed a framework to identify and isolate pavement markings from  LiDAR point clouds, to filter and refine data, and to produce models and evaluate the associations between field- measured retroreflectivity and a combination of intensity from LiDAR readings, RGB data, and marking material.  Freeway data was used to analyze the potential of LiDAR in assessing the retroreflectivity of pavement markings. Results show that LiDAR data can produce reliable associations to retroreflectivity levels both in terms of classification and value prediction to make maintenance decisions. A key component in the proposed methodology for prediction and classification is the clustering of individual assessments spatially correlated to produce robust segment-level outcomes. This study is complemented by a computer tool that implements the analysis methods and allows for processing of new datasets. In addition, a related project extends the work presented here to incorporate imagery into the analysis for more comprehensive assessments.]]></description>
      <pubDate>Thu, 30 Jul 2026 10:08:49 GMT</pubDate>
      <guid>https://trid.trb.org/View/2732496</guid>
    </item>
    <item>
      <title>Evaluation of Retroreflective Pavement Markers for Precision and Nonprecision Runways</title>
      <link>https://trid.trb.org/View/2724664</link>
      <description><![CDATA[The purpose of this program was to evaluate the use of retroreflective pavement markers, installed in a configuration duplicating runway centerline and touchdown zone lighting system of a Category II runway on Category I or Nonprecision Approach runways with edge lighting to determine if these retroreflective markers will enhance nighttime visual guidance to provide increased safety of operations and possible reduction in minimums, particularly under wet runway conditions. Visual contact height with the retroreflective pavement marker systems was not enhanced prior to reaching Minimum Descent Altitude (MDA) or Decision Height (DH) for nonprecision or Category I approaches respectively; therefore, this system will not permit the reduction in approach minimums for Category I precision or nonprecision approaches. However, the test program demonstrated that the system is effective in improving the safety of operation for final approach, flare and touchdown, landing rollout, and for takeoffs. Particularly under rainy, wet nighttime conditions, the pavement retroreflector significantly enhanced the visual guidance, supplementing that provided by the standard runway edge lights and paint markings which are difficult to see under wet conditions.]]></description>
      <pubDate>Mon, 20 Jul 2026 17:04:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/2724664</guid>
    </item>
    <item>
      <title>Follow-On Friction Testing of Retro-Reflective Glass Beads</title>
      <link>https://trid.trb.org/View/2694510</link>
      <description><![CDATA[In 1993 and 1994 the Federal Aviation Administration (FAA) Technical Center conducted an evaluation of retro-reflective beads in airport pavement markings. That study proved that the addition of glass beads greatly enhanced the conspicuity of the surface markings. In the study the beaded stripes had a silica (sand) friction enhancement added to the paint. A concern arose as to the friction characteristics of beaded paint without silica. The current study was conducted to test the friction levels of painted surface markings with and without beads and/or silica. Results of this study indicate that the friction levels of surface painted markings can be increased by adding retro-reflective glass beads to the paint. Silica also increased the friction of the surface markings; however, when glass beads were also added, the benefit of silica was reduced due to its smaller size in relation to the size of the beads.]]></description>
      <pubDate>Sat, 16 May 2026 17:03:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2694510</guid>
    </item>
    <item>
      <title>Predicting Retroreflectivity Degradation of Pavement Marking Using a Bayesian Ordered Logit Model</title>
      <link>https://trid.trb.org/View/2701298</link>
      <description><![CDATA[Adequate pavement marking retroreflectivity RL is crucial in enhancing road safety, and cost-effective marking restriping planning requires RL deterioration models and service life estimation. This paper presents the Bayesian ordered logit model that incorporates Markov Chain Monte Carlo simulation to predict the degradation trend in RL using data collected from representative highways in Wyoming. The results indicate that the marking age and characteristics, geometric locations, pavement surface, traffic volume, and snowplow operations are the significant factors affecting pavement marking degradation. The results indicate that the lane line and center line are more prone to degradation compared with the edge line. In addition, the degradation rate is higher for white markings than for yellow markings and in the curve section compared with the straight section. Cumulative traffic, truck traffic passage, and snowplow operation also significantly affect RL degradation. The outcomes derived from the distinct models reveal substantial differences among the three functional classification models and justify investigating separate models. By integrating the random intercept into the modeling process, the analysis found a notable presence (from 22% to 31%) of unobserved heterogeneity within the same route, a crucial aspect that ensures the attainment of accurate and unbiased results. This paper also proposed a prediction equation to determine pavement marking service lives and reveals that the service life of different materials varies based on road classification, marking material, and line position. The proposed model is readily implementable and can assist pavement marking management by effectively scheduling restriping and maintenance periods for different materials.]]></description>
      <pubDate>Fri, 15 May 2026 09:18:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/2701298</guid>
    </item>
    <item>
      <title>Development of a Device to Evaluate the Retro-Reflective Performance of Pavement Marking Materials</title>
      <link>https://trid.trb.org/View/2683251</link>
      <description><![CDATA[The objective of this research study was to investigate possible techniques for measuring the brightness of the retro-reflective pavement markings on a highway surface. The measurements were to be made during daylight hours and from a moving vehicle. A practical field device, or instrument, was then to be designed and developed. During the course of the project, one major change was made in the objective. This was to measure the contrast of the stripe to its background rather than stripe luminance only. A bench prototype of the optical system and the servo controlled tracking system has been constructed and tested in the laboratory. This report discusses the system requirements, the design approaches considered, the prototype tracking system and the proposed design of the complete device.]]></description>
      <pubDate>Mon, 20 Apr 2026 18:10:32 GMT</pubDate>
      <guid>https://trid.trb.org/View/2683251</guid>
    </item>
    <item>
      <title>A Novel Low-Cost Double U-Net Model for Predicting Traffic Sign Retro-Intensity from Camera Data</title>
      <link>https://trid.trb.org/View/2691791</link>
      <description><![CDATA[Retroreflectivity is essential for the visibility of transportation infrastructure, ensuring road safety, especially under low-light conditions. Traditional methods for measuring retroreflectivity, such as nighttime visual inspections and retroreflectometer measurements, are labor-intensive, subjective, and pose safety risks. With the introduction of lidar technology, traffic sign retroreflectivity can be assessed more efficiently, as lidar-derived reflectivity values demonstrate a strong linear correlation with retroreflectivity. This study leverages a lidar device to propose a Double U-Net framework for predicting pixel-level reflectivity from daytime red, green, blue (RGB) images, providing a localized and accurate prediction. To train the Double U-Net model, a structured data set of over 7,600 images of transportation infrastructure was created, incorporating lidar-derived depth and reflectivity data. Given the sparsity of low-resolution lidar point clouds, linear interpolation was applied to generate pixel-level depth and reflectivity images. The proposed Double U-Net framework employs a two-stage architecture, where depth is predicted from cropped images in the first stage, and then combined with the original image and class embeddings in the second stage to generate pixel-level reflectivity predictions. A weighted loss function balances depth and reflectivity errors, enhancing prediction accuracy and robustness. The model achieved a median mean square error (MSE) of 0.0162 with interpolated data, 0.02233 with raw data, a median structural similarity index measure (SSIM) of 0.5413, and a Mann-Whitney U Test alignment of 58.2% with raw reflectivity data at a 0.001 significance level. The model effectively captures localized defects on traffic signs, providing a more detailed analysis compared with traditional methods.]]></description>
      <pubDate>Wed, 15 Apr 2026 11:31:04 GMT</pubDate>
      <guid>https://trid.trb.org/View/2691791</guid>
    </item>
    <item>
      <title>Modernizing NDOT's Pavement Marking Program for Retroreflectivity Compliance and Cost-Effective Restriping </title>
      <link>https://trid.trb.org/View/2689409</link>
      <description><![CDATA[The evaluation of pavement marking materials primarily relies on their retroreflectivity, which is the measure of how effectively markings reflect vehicle headlight illumination back toward the driver. Deciding when pavement markings need to be restriped is not straightforward because their visibility depends on retroreflectivity. Nebraska Department of Transportation (NDOT) currently follows a pavement marking policy that is last updated over twenty years ago. The practice is based on fixed restriping frequencies (e.g., annually) determined by corridor type and traffic volume. The Federal Highway Administration (FHWA) requires all agencies to implement a pavement marking retroreflectivity maintenance method by September 6, 2026, and specifies minimum maintained retroreflectivity values of 50 mcd/m²/lx for roadways with posted speeds ≥ 35 mph and 100 mcd/m²/lx for speeds ≥ 70 mph. NDOT does not yet maintain a comprehensive or statewide pavement marking retroreflectivity dataset. Without historical measurements or geographically representative data, it cannot characterize how different marking materials deteriorate across Nebraska’s diverse traffic and climate conditions. This lack of data limits NDOT’s ability to transition from a frequency-based to a performance-based maintenance strategy that meets FHWA requirements, manages costs, and improves operational efficiency. The overall goal of this research project is to provide NDOT with a documented, MUTCD-compliant, and data-driven method for maintaining pavement marking retroreflectivity that ensures safety, regulatory compliance, and cost-effective use of maintenance resources. To achieve this goal, the project will pursue the following specific objectives: develop a Nebraska-specific hybrid maintenance method, develop a statistically sound statewide data-collection plan, develop and calibrate degradation models, and quantify expected life-cycle benefits.]]></description>
      <pubDate>Tue, 02 Jun 2026 12:26:55 GMT</pubDate>
      <guid>https://trid.trb.org/View/2689409</guid>
    </item>
    <item>
      <title>Barrier Striping for the Reduction of Accidents</title>
      <link>https://trid.trb.org/View/2676924</link>
      <description><![CDATA[Barrier striping is a roadway safety countermeasure designed to enhance driver awareness of concrete barriers, particularly under adverse weather and low-visibility conditions. This study evaluated the short- and long-term safety effectiveness of retroreflective barrier striping across multiple sites in Texas. The research involved a comprehensive literature review of barrier delineation practices, a detailed examination of existing installations, and the implementation and evaluation of new treatments at selected high-crash locations. Data collection included crash records, roadway geometry, traffic volume, meteorological conditions, and probe vehicle speed data. Analytical methods encompassed descriptive statistics, crash rate comparisons, logistic and linear regressions, Negative Binomial, and survival analysis to assess the impact of striping on crash frequency, severity, and operating speeds. The findings revealed notable reductions in barrier-related crashes at treated sites, with relatively stronger improvements observed at nighttime, underscoring the benefits of increased retro-reflectivity. Speed analysis suggested limited but measurable effects on vehicle operating behavior. Based on these results, the project team refined the Texas Department of Transportation’s draft special specification for barrier striping, offering updated guidance on materials, spacing, and installation procedures. Overall, barrier striping demonstrates promising potential as an effective countermeasure to improve roadway safety, though continued evaluation and site-specific considerations are recommended. Future research should further explore surrogate safety measures, maintenance requirements, and the effectiveness of alternative striping materials.]]></description>
      <pubDate>Fri, 13 Mar 2026 08:45:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/2676924</guid>
    </item>
    <item>
      <title>Microplastics from road markings: the loss of drop-on glass beads as a signal of emissions</title>
      <link>https://trid.trb.org/View/2647827</link>
      <description><![CDATA[Abrasion of road markings was reported as a meaningful sources of microplastic pollution. Whereas field research indicated that it was a rare event because of the protective role of glass beads always strewn on the surface of road markings, laboratory research under controlled conditions was due. To fulfil this knowledge gap, two exemplary road marking paints were tested with a wear simulator and the collected abraded material was analysed for the presence of microplastic particles. The outcome indicated major dissimilarities between the paints in terms of resistance to abrasion and a clear correlation between the extraction of the glass beads from the film and the emissions of microplastics. Hence, the protective role of glass beads was confirmed: if renewed promptly, road markings should be considered as negligible contributors to microplastic pollution.]]></description>
      <pubDate>Fri, 20 Feb 2026 15:28:26 GMT</pubDate>
      <guid>https://trid.trb.org/View/2647827</guid>
    </item>
    <item>
      <title>Literature overview of road marking performance with emphasis on application technique and used materials</title>
      <link>https://trid.trb.org/View/2627539</link>
      <description><![CDATA[Road markings represent an essential element of effective traffic management, serving as visual guidance for drivers and playing a key role in road traffic safety. The primary objective of this article is to provide a comprehensive overview of the most relevant previous research related to the performance of road markings, with a particular focus on their durability and skid resistance, depending on the application techniques and materials used. Utilizing the PRISMA methodology and the "Snowballing" method, the literature review encompassed scientific articles published in journals and conference proceedings. The articles were divided into two main groups according to their research focus: (1) articles dealing with the durability of road markings depending on the material and method of application (24 articles), and (2) articles addressing the skid resistance coefficient of road markings depending on the materials used (5 articles). The results of the analysed studies significantly contribute to the optimization of road marking maintenance; however, further research is required to verify and expand the proposed models. Future studies should consider model validation on a larger sample of roads from different climatic regions, as well as the inclusion of additional variables such as the quality of glass beads, type and condition of the road surface, salt application, incorporation of anti-skid particles, and similar factors. This would ensure greater applicability and accuracy of the models under varying conditions, ultimately contributing to the optimization of road marking maintenance and the enhancement of road traffic safety.]]></description>
      <pubDate>Tue, 27 Jan 2026 16:16:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2627539</guid>
    </item>
    <item>
      <title>Detectability of pedestrian crossing road markings: comparison of optical and thermal cameras</title>
      <link>https://trid.trb.org/View/2627515</link>
      <description><![CDATA[This study investigated the detectability of road markings across various pedestrian crossings, applying both standard (optical) and thermal cameras. Four different crossings were evaluated: milled pedestrian crossing on asphalt, pedestrian crossing with white thin-layer road marking on asphalt, raised pedestrian crossing with white thin-layer road marking on cobblestone, and pedestrian crossing with white and red thick-layer structured road marking on asphalt. The research was conducted under dry and wet conditions both during daytime and nighttime. Contrast ratio values calculated from both camera recordings were compared with values of road marking parameters measured by a retroreflectometer. The results demonstrated how various road markings on different surface influenced the detectability of pedestrian crossings, particularly under varying the times of day and weather conditions. The use of a thermal camera proved valuable to assess road markings under unfavourable conditions, such as nighttime or wet surfaces, where data from a standard camera may have been inadequate. The study outcomes provided insights, which could impact the development of improved guidelines for road marking maintenance and design, ensuring better detectability and, as a consequence, safer pedestrian crossings.]]></description>
      <pubDate>Tue, 27 Jan 2026 16:16:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2627515</guid>
    </item>
    <item>
      <title>Comparative analysis of nighttime pavement marking perception among drivers of different ages: A real-world driving study</title>
      <link>https://trid.trb.org/View/2652412</link>
      <description><![CDATA[Pavement markings are essential for conveying lane boundaries, alignment, and other traffic information to drivers. Their visibility is closely tied to drivers' visual capabilities, which often decline with age. These age-related impairments can hinder drivers’ ability to perceive road markings at night, posing potential safety risks. To investigate age-related differences in nighttime perception of pavement markings, this study designed a real-world driving experiment using white pavement markings with nine levels of coefficient of retroreflected luminance (R[subscript L]). A total of 360 preview distance observations were collected from 40 participants, including 14 young, 14 middle-aged, and 12 older adults. A generalized linear mixed model (GLMM) was employed to examine how R[subscript L], age, and gender influence nighttime preview distance. In addition, an age-stratified asymptotic regression model was developed to capture the nonlinear relationship between R[subscript L] and preview distance. The results showed that: (1) R[subscript L] was positively associated with preview distance, while age had a significant negative effect. Gender differences were not statistically significant. (2) There was no significant difference between young and middle-aged drivers, but old drivers had preview distances 14.7%–31.0% shorter under the same R[subscript L] conditions. (3) At driving speeds between 60 and 100 km/h, the R[subscript L] threshold required to ensure safe visibility for elderly drivers was 1.58–1.70 times higher than that for young to middle-aged drivers. These findings provide practical insights for transportation planners and policymakers in aging societies, highlighting the need for age-sensitive standards in pavement marking design to enhance nighttime driving safety for elderly road users.]]></description>
      <pubDate>Mon, 26 Jan 2026 14:44:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/2652412</guid>
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