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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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    <item>
      <title>Marginal infrastructure costs and pricing in road and rail transport</title>
      <link>https://trid.trb.org/View/2752028</link>
      <description><![CDATA[This licentiate thesis examines marginal cost estimation and pricing in transport infrastructure, with empirical applications to Swedish roads and railways. The thesis consists of three papers addressing how infrastructure charges can be aligned with short-run marginal social costs. The first paper estimates marginal road renewal costs per heavy vehicle kilometre using panel data on approximately 1.3 million 100 meter road segments (1999-2022.. The second paper estimates short-run marginal road maintenance costs per heavy vehicle kilometre using administrative maintenance data at the Maintenance District Unit (MDU) level (2015-2024.. The third paper analyses optimal rail access charges in a vertically separated railway market, where marginal capacity costs reflect track congestion.]]></description>
      <pubDate>Fri, 07 Aug 2026 08:35:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/2752028</guid>
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    <item>
      <title>A participatory approach to objective and data-driven condition assessment of gravel roads</title>
      <link>https://trid.trb.org/View/2751984</link>
      <description><![CDATA[Gravel roads play a vital role in transportation, particularly in rural and remote regions. They support essential sectors such as agriculture, forestry, tourism, and emergency services and can serve as access routes to remote natural resources or large onshore windmill farms. However, they deteriorate rapidly and rely on subjective, inconsistent and labour-intensive visual and manual condition assessment, often resulting in delayed maintenance interventions and costly maintenance actions. This dissertation addresses the need for improved condition assessment of gravel roads by integrating participatory approaches with objective data-driven methods. Overcoming limitations of traditional assessment practices would enable broader network coverage, enhance the efficiency and effectiveness of defect detection, and support sustainable maintenance planning and informed decision-making. The research is guided by Design Research Methodology, synthesising the six appended interrelated studies. These studies progress from problem identification and conceptual development to a case study and empirical field experiments to answer the three research questions (RQs): (1. How can objective data-driven approaches address the limitations of traditional approaches to enable efficient and effective assessment of gravel road conditions? (2. How can data-driven approaches and multi-source information enable reliable assessment of gravel road conditions and support maintenance planning and decision-making? (3. How can participatory and adaptive gravel road condition data collection enable sustainable condition assessment to support predictive and data-driven maintenance planning and decision-making?]]></description>
      <pubDate>Fri, 07 Aug 2026 08:35:01 GMT</pubDate>
      <guid>https://trid.trb.org/View/2751984</guid>
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    <item>
      <title>Objective assessment of loose gravel condition using machine learning with audio-visual observation</title>
      <link>https://trid.trb.org/View/2491216</link>
      <description><![CDATA[A well-maintained road network is essential for sustainable economic development, providing vital transportation routes for goods and services while connecting communities. Sweden's public road network includes a significant portion of gravel roads, particularly cost-effective for less populated areas with lower traffic volumes. However, gravel roads deteriorate quickly, leading to accidents, environmental pollution, and vehicle tire wear when not adequately maintained. The Swedish Road Administration Authority (Trafikverket) assesses gravel road conditions using subjective methods, analysing images taken during snow-free periods. Due to cost constraints, this labour-intensive process is prone to errors and lacks advanced techniques like road profilometers. This thesis explores the field of assessing gravel road conditions. It commences with a comprehensive review of manual gravel road assessment methods employed globally and existing data-driven smart methods. Subsequently, it harnesses machine hearing and machine vision techniques, primarily focusing on enhancing road condition classification by integrating sound and image data. The research examines sound data collected from gravel roads, exploring machine learning algorithms for loose gravel conditions classification with potential road maintenance and monitoring implications. Another crucial aspect involves applying machine vision to categorise image data from gravel roads. The study introduces an innovative approach using publicly available resources like Google Street View for image data collection, demonstrating machine vision's adaptability in assessing road conditions. The research also compares machine learning methods with manual human classification, specifically regarding sound data. Automated approaches consistently outperform manual methods, providing more reliable results. Furthermore, the thesis investigates combining audio and image data to classify road conditions, particularly loose gravel scenarios. Early feature fusion using pre-trained models significantly improves classifier accuracy.]]></description>
      <pubDate>Fri, 17 Jan 2025 15:16:35 GMT</pubDate>
      <guid>https://trid.trb.org/View/2491216</guid>
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    <item>
      <title>On the establishment of a data-driven approach to gravel road maintenance</title>
      <link>https://trid.trb.org/View/2388997</link>
      <description><![CDATA[Gravel roads are essential for economic development as they facilitate the movement of people, transportation of goods and services, and promote cultural and social development. They typically connect sparsely populated rural areas to urban centres, providing essential access for residents and entrepreneurs. Maintaining these roads to an acceptable level of service is crucial for the efficient and safe transportation of goods and services. However, substantial maintenance investment is required, yet resources are limited. Gravel roads are prone to dust, potholes, corrugations, rutting and loose gravel. They deteriorate faster than paved roads, and their failure development is affected by traffic action and physical, geometric and climatic factors. Thus, more condition monitoring and proper road condition assessment are necessary for dynamic maintenance planning to reach efficiency and effectiveness using objective, data-driven condition assessment methods to ensure all-year-round access. However, objective data-driven methods (DDMs) are not frequently used for gravel road condition assessment, and where they have been applied, the practical implementation is limited. Instead, visual windshield assessment and manual methods are predominant. Visual assessments are unreliable and susceptible to human judgement errors, while manual methods are time-consuming and labour-intensive. Maintenance activities are predetermined despite dynamic maintenance needs, and the planning is based on historical failure data rather than the actual road condition. This thesis establishes a data-driven approach to gravel road maintenance describing the systematic assessment of the gravel road condition and collection of the condition data to ensure efficient and effective maintenance planning. This thesis uses a design research methodology based on a literature review, concept development, interview study and field experiments.]]></description>
      <pubDate>Mon, 10 Jun 2024 14:05:08 GMT</pubDate>
      <guid>https://trid.trb.org/View/2388997</guid>
    </item>
    <item>
      <title>BVFF Grusslitlager och stödremsa med inblandning av filler från asfaltstillverkning</title>
      <link>https://trid.trb.org/View/2269688</link>
      <description><![CDATA[The project aims to improve the construction of road construction materials of crushed rock. This applies in particular to materials for gravel road surface layers and support strips that are dependent on (relatively) high fine grain levels. Usually, a mixture of fine material is required for crushed rock to meet TrV's requirements for fine grain content. The fine material provides gravel wear layers: tightness, the bondage, moisture-retaining properties (against dusting). In the production of asphalt, excess filler occurs. This surplus is difficult to find a provision for. For a more sustainable construction of civil engineering infrastructure, a more resource-efficient use of this surplus is needed. The project will solve the problem by: Developing a number of recipes for mixtures; Evaluating them after laboratory tests; Selecting appropriate suggestions; Producing materials at full scale; Building test routes; Evaluating the test routes. The result will lead to knowledge of how the function of materials for gravel wear bearings and support strips changes with different levels of involvement of excess fillers from asphalt plants. The knowledge can be used to revise existing requirements in case the result shows that sufficient or improved function is obtained through interference. Suppliers of aggregate can use the knowledge to make better use of the surplus of fine materials. The project will lead to knowledge of a cost-effective production method for the involvement of filler.]]></description>
      <pubDate>Mon, 16 Oct 2023 09:26:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/2269688</guid>
    </item>
    <item>
      <title>Staged Road Construction in Very Weak Subgrade Using Polymeric Geocell</title>
      <link>https://trid.trb.org/View/2260249</link>
      <description><![CDATA[The ongoing development of the energy industry in Canada, especially for pipeline-related structures, demands innovative ways of access construction. Most of these are at remote locations and under difficult geotechnical conditions making access a challenge. A 4.1km long unpaved access road leading to a proposed compressor station in Blainville, Quebec was planned for the construction of the station pad and future access. The road was expected to serve as a material haul road for the 200m x 250m gravel pad, regular compressor station construction loads, and future traffic. Construction of the pad was scheduled to start before the winter of 2020. The proposed road alignment had very soft to soft subgrade conditions with saturated peat. There were problems with limited right of way, a landslide-prone zone, a creek crossing, and overhead power lines. The road geometry was to be designed such that there was enough clearance from the overhead power lines and the slide-prone area and maintain the minimum turning radius required for the long and heavy trucks carrying compressor units. Additionally, there were constraints imposed in permits and other aspects of the project that left a short 6-week window for the construction of the road.]]></description>
      <pubDate>Mon, 09 Oct 2023 09:12:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/2260249</guid>
    </item>
    <item>
      <title>Laboratory assessment of gravel wearing course stabilization under various climate conditions</title>
      <link>https://trid.trb.org/View/2145655</link>
      <description><![CDATA[The purpose of this research is to investigate the efficacy of stabilizing local gravel wearing course (GWC) and assessing the possibilities and weaknesses of five non-traditional stabilizing agents to improve the properties of the selected GWC. The main research is based on carrying out laboratory light weight deflectometer (LWD) tests to evaluate the deformation characteristics of unstabilized and stabilized GWC mixtures compacted in CBR molds.  A laboratory experimental test program was conducted to evaluate the effect of freeze-thaw cycles and soaking-drying cycles on the properties of stabilized and unstabilized GWC samples. The treatments were manifested in adding 1) recommended dosage of clay only, 2) DUST/BLOKR (DBSB), 3) Listab, 4) esoliTSS, 5) clay with Road stabilizer (RS) and 6) clay with TerraZyme (TZ), to the chosen GWC. The series of unstabilized GWC was used as a control group.  The results of this research showed that for GWC samples unexposed to climate simulation, the maximum decrease in average deformations was 13% for GWC stabilized with esoliTSS followed by 11% for samples stabilized with DBSB.  After exposing the samples to ten freeze-thaw cycles “FTCs”, the GWC samples stabilized with DBSB was the only group suffered from noticeable damage. The total increase in the average deformation was about 18.4% as compared to untreated GWC samples exposed to the same number of FTCs. On the other hand, the GWC samples with esoliTSS showed best performance after exposing to FTCs.  With respect to samples exposed to five soaking-drying cycles (SDCs), the GWC samples treated with DBSB showed about 23% increase in deformations compared to the reference exposed to five SDC, (and hence a reduction in stability). Also, the GWC samples treated with DBSB recorded 17% higher deformations due to SDCs as compared to untreated GWC samples exposed to same number of SDC. The GWC samples stabilized with esoliTSS and Listab performed best after exposing to SDCs.]]></description>
      <pubDate>Mon, 03 Apr 2023 16:45:35 GMT</pubDate>
      <guid>https://trid.trb.org/View/2145655</guid>
    </item>
    <item>
      <title>Development and Field Experience with Performance-Based Asphalt Mixture Used in Thin Asphalt Pavement</title>
      <link>https://trid.trb.org/View/1930564</link>
      <description><![CDATA[This paper presents an asphalt mixture solution that can be placed as a thin layer (less than 40 mm) over granular base to provide a hard-top driving surface. This paper further provides steps in understanding the response of the mix and steps required to translate such responses into developing a performance-based requirement for the asphalt mix. The performance-based design steps are explained in this paper to provide an insight into how low-temperature flexibility and long-term fatigue behaviour of a mix is assessed and related to repetitive stresses expected from low to medium level of traffic coupled with environmental conditions expected in Southern Ontario. Production and paving experience with this asphalt mix solution are also included in this paper, as well as more than two-year field performance of a trial section in Southern Ontario.]]></description>
      <pubDate>Tue, 22 Mar 2022 14:50:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/1930564</guid>
    </item>
    <item>
      <title>Automated gravel road condition assessment : a case study of assessing loose gravel using audio data</title>
      <link>https://trid.trb.org/View/1894917</link>
      <description><![CDATA[Gravel roads connect sparse populations and provide highways for agriculture and the transport of forest goods. Gravel roads are an economical choice where traffic volume is low. In Sweden, 21% of all public roads are state-owned gravel roads, covering over 20,200 km. In addition, there are some 74,000 km of gravel roads and 210,000 km of forest roads that are owned by the private sector. The Swedish Transport Administration (Trafikverket) rates the condition of gravel roads according to the severity of irregularities (e.g. corrugations and potholes), dust, loose gravel, and gravel cross-sections. One of the essential parameters for gravel road assessment is loose gravel. Loose gravel can cause a tire to slip, leading to a loss of driver control. Assessment of gravel roads is carried out subjectively by taking images of road sections and adding some textual notes. A cost-effective, intelligent, and objective method for road assessment is lacking. Expensive methods, such as laser profiler trucks, are available and can offer road profiling with high accuracy. These methods are not applied to gravel roads, however, because of the need to maintain cost-efficiency. In this thesis, we explored the idea that, in addition to machine vision, we could also use machine hearing to classify the condition of gravel roads in relation to loose gravel. Several suitable classical supervised learning and convolutional neural networks (CNN) were tested. When people drive on gravel roads, they can make sense of the road condition by listening to the gravel hitting the bottom of the car. The more we hear gravel hitting the bottom of the car, the more we can sense that there is a lot of loose gravel and, therefore, the road might be in a bad condition. Based on this idea, we hypothesized that machines could also undertake such a classification when trained with labeled sound data. Machines can identify gravel and non-gravel sounds.]]></description>
      <pubDate>Wed, 01 Dec 2021 14:46:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/1894917</guid>
    </item>
    <item>
      <title>Effekt av dammbindningsmedel : en laboratoriestudie</title>
      <link>https://trid.trb.org/View/1875953</link>
      <description><![CDATA[In this study, calcium chloride and magnesium chloride have been evaluated in combination with four different fine materials (granite, amphibolite, meta greywacke and naturally occurring silt), which are used for gravel road maintenance. Aqueous solutions of the two salts have been added to the fine material where after rain and drying has been simulated under laboratory conditions. Evaluation has been performed in terms of residual amount of salt after rain simulation, and SEM and optical microscopy on the fine material after drying, respectively It has been difficult to draw any conclusions that would yield new information from the tests. The methodology developed was not able to show agglomeration in the fine fraction of the gravel road material and it was not possible to provide recommendations regarding the dosage of dust binding agents. The tests show that calcium chloride is more efficient in retaining moisture than magnesium chloride when the comparison is based on the amount of flakes used. Agglomeration could not be proven despite several repeated tests. The chemical properties did not differ significantly, the salts behaved similarly and according to earlier known data. Differences in the origin of rock material was negligible compared with the effects of the salts. The added salt was for the most part (with a minimum of 80%) leached out during the rain simulation. No differences between calcium chloride and magnesium chloride or between the different fine materials were observed in terms of leaching. A small difference between leaching of cations and anions was recorded where the cations were retained in the fine material. This might be an ion-exchange effect. Analysis with SEM and optical microscopy did not yield any significant differences between the different combinations of salt and fine materials, respectively. During drying of the fine material it was observed that calcium chloride, calculated as commercial product, could absorb more water than magnesium chloride. This effect persisted also after the rain simulation. The experimental method that was developed during the study did not give any, previously not known, differences between the different salts and fine materials. Probably the system has been simplified to such an extent that relevant parameters were removed or do not reflect real field conditions.]]></description>
      <pubDate>Wed, 01 Sep 2021 14:25:32 GMT</pubDate>
      <guid>https://trid.trb.org/View/1875953</guid>
    </item>
    <item>
      <title>Cohesive Clays for Construction and Stabilization of Unpaved Roads</title>
      <link>https://trid.trb.org/View/1754880</link>
      <description><![CDATA[Cohesive clays and organic catalysts are tested and used for the construction and stabilization of the wearing surface of unpaved haulage and high-maintenance municipal roads in Manitoba. The process requires a typical A-base aggregate with good particle size distribution and a very high (>25%) fines and clay content. For this application, the inherent electronic bonding potential of natural reactive clay is harnessed to maximize clay to clay mineral bonding while limiting clay to water bonding and water ingress. Catalysts are used to promote densification, clay bonding with cationic polymers (present in natural soils and in the catalyst), and water egress. The result is a strong, semi-permanent clay cemented matrix that effectively bonds the aggregate mix. This produces a dense road surface with high bearing strength, superior durability, excellent road functionality, and low maintenance requirements. Only natural materials are used with no deletrious environmental impacts, and dust is reduced to a minimal level. An added benefit is the significant reduction in the use of high-quality aggregates, extending the life of known resources. Both high-traffic heavy haul roads and municipal roads have been construction and monitored in the Brandon region over the past five years, with no indication yet when the road surfaces will require a significant upgrading or reconstruction. This paper discusses the electronic bonding properties of clays, how and why the process works, the types of materials that can be used, road performance to date, and some of the applications where these types of roads can be very beneficial in terms of performance, cost and environmental impact.]]></description>
      <pubDate>Tue, 01 Dec 2020 13:58:05 GMT</pubDate>
      <guid>https://trid.trb.org/View/1754880</guid>
    </item>
    <item>
      <title>Defining Needs for Optimized Management of Gravel Road Networks</title>
      <link>https://trid.trb.org/View/1563623</link>
      <description><![CDATA[Unpaved roads account for approximately 60% of Canada’s public road network. Maintaining gravel roads is a major activity for many municipalities and requires regular interventions to provide smooth and safe riding surfaces for road users. Municipalities spend millions of dollars every year on gravel road maintenance and rehabilitation activities. A comprehensive road management system that includes their gravel road network could significantly improve a municipality’s ability to manage their operating and capital budgets. In 2017, the authors undertook a survey of Canadian municipalities related to gravel road maintenance practices. A total of 97 municipalities responded to the survey, representing around 40,000 km of gravel roads. The survey’s main goal was to capture the state-of-practice in gravel road management used by Canadian municipalities and to investigate to what extent municipalities collect data about their gravel roads. This paper discusses the results of that survey and investigates the need for better decision support tools to manage gravel roads. The paper also discusses the required components of a gravel road management system (GRMS), key operational and maintenance consideration, and the implementation of a GRMS through a case study.]]></description>
      <pubDate>Tue, 16 Oct 2018 14:04:37 GMT</pubDate>
      <guid>https://trid.trb.org/View/1563623</guid>
    </item>
    <item>
      <title>Estimated lifetimes of road pavements in Sweden using time-to-event analysis</title>
      <link>https://trid.trb.org/View/1506381</link>
      <description><![CDATA[Maintenance planning of road pavement requires reliable estimates of roads' lifetimes. In determining the lifetime of a road, this study combines maintenance activities and road condition measurements. The scope of the paper is to estimate lifetimes of road pavements in Sweden with time to event analysis. The model used includes effects of pavement type, road type, bearing capacity, road width, speed limit, stone size and climate zone, where the model is stratified according to traffic load. Among the nine analyzed pavement types, stone mastic had the longest expected lifetime, 32 percent longer than asphalt concrete. Among road types, ordinary roads with cable barriers had 30 percent shorter lifetime than ordinary roads. Increased speed lowered the lifetime, while increased stone size (up to 20 mm) and increased road width lengthened the lifetime. The results are of importance for life cycle cost analysis and road management.]]></description>
      <pubDate>Wed, 28 Mar 2018 10:22:43 GMT</pubDate>
      <guid>https://trid.trb.org/View/1506381</guid>
    </item>
    <item>
      <title>Marginal cost of road maintenance and operation: Swedish estimates based on data from 2004 to 2014</title>
      <link>https://trid.trb.org/View/1492559</link>
      <description><![CDATA[In this study, we estimated the marginal costs of road operation and maintenance by using the cost function approach with Swedish road network data from 2004 to 2014. The results of this study suggest a marginal cost of 0.07 SEK per vehicle kilometre for maintenance and operation of gravel roads, but none for paved roads. The data consist of traffic volume, costs, and road attributes for the Swedish national road network. The observational unit is the road maintenance delivery unit (MDU), and there were 109 such MDUs in Sweden in 2014. We estimated models separately for paved road operation and maintenance, gravel road operation and maintenance, and winter road operations. In paved road maintenance, reinvestment is excluded. The data are given in panel format and the models are estimated with random effects. A logarithmic functional form has been used, and this means that the estimated parameter can be interpreted as an elasticity. This elasticity together with the average cost yields the marginal cost. The results of this study suggest a marginal cost of 0.07 SEK per vehicle kilometre for maintenance and operation of gravel roads. The estimated marginal cost for winter road operation is less than 0.01 SEK per vehicle kilometre, and this marginal cost estimate is statistically significant. We do not find a statistically significant marginal cost for maintenance and operation of paved roads. Our estimates of marginal costs for road maintenance and operation are generally lower compared to previous Swedish estimates. An important reason for this is that the definition of an MDU has changed over time, but we used the current classification for each year of data in this report. The lack of a significant marginal cost for paved roads is most likely explained by the fact that reinvestment costs were not included in our analysis. We have tested other model specifications to check the robustness of our results. The estimates are robust with respect to different time periods, the choice of measure of traffic volume, and new explanatory variables, except in the case of the gravel roads.]]></description>
      <pubDate>Tue, 19 Dec 2017 11:29:29 GMT</pubDate>
      <guid>https://trid.trb.org/View/1492559</guid>
    </item>
    <item>
      <title>The evidence for rural road technology in low-income countries</title>
      <link>https://trid.trb.org/View/1440319</link>
      <description><![CDATA[]]></description>
      <pubDate>Mon, 19 Dec 2016 11:23:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/1440319</guid>
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