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    <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" />
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    <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>
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      <title>Transport Research International Documentation (TRID)</title>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
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    <item>
      <title>A rational approach to select the number of field tests required to determine subgrade properties</title>
      <link>https://trid.trb.org/View/1639939</link>
      <description><![CDATA[This paper presents a rational approach to answer the questions of how many field tests need to be performed at a test site to determine its subgrade strength properties, and what inferences can be drawn from limited number of field tests. MATLAB simulations were performed to generate various data sets that corresponded to site variability, with the coefficient of variation (CoV) ranging from 10 to 80%. Studies were performed based on coefficient of variation (CoV) and regression analysis. This study provides two important charts for evaluating subgrade properties at test sites: (1) to determine the number of field tests to be performed, after which there would not be any significant change in the inferences drawn from the test results; (2) inferences pertaining to subgrade soil property of a field test site, based on a limited number of tests. In order to demonstrate the applicability of the charts developed through this research, light weight deflectometer (LWD) spot tests, that were performed at a test site, were considered. The results were used to draw inferences about the modulus of the subgrade material and the possible variability of the test site, in addition to the maximum number of tests that might be performed.]]></description>
      <pubDate>Tue, 30 Jul 2019 15:56:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/1639939</guid>
    </item>
    <item>
      <title>Precision of modal analysis to characterise the complex modulus of asphalt concrete</title>
      <link>https://trid.trb.org/View/1607370</link>
      <description><![CDATA[Modal analysis is an economic and efficient test method to characterise the complex modulus of asphalt concrete. In this paper, the precision of modal analysis was evaluated by performing testing at several laboratories on two cylindrical asphalt concrete specimens. In addition, the complex moduli characterised by modal analysis were compared to cyclic tension-compression testing. The results showed that the coefficient of variation was less than 3% at loading frequencies above 10 Hz for the complex modulus determined through modal analysis. The comparison of the complex modulus determined from modal analysis and tension-compression testing resulted in a coefficient of variation values not more than 9% for loading frequencies ranging from 0.1 to 109 Hz.]]></description>
      <pubDate>Wed, 29 May 2019 17:04:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/1607370</guid>
    </item>
    <item>
      <title>Development of a rate-dependent cumulative work and instantaneous power-based asphalt cracking performance index</title>
      <link>https://trid.trb.org/View/1607344</link>
      <description><![CDATA[Use of the semi-circular bending (SCB) test has gained popularity for evaluating cracking performance of asphalt mixtures. An Illinois Flexibility Index Test (I-FIT) variant of SCB has shown the ability to distinguish mixtures through use of the flexibility index (FI) parameter. While this index has been able to rank the mixtures with respect to performance, a high coefficient of variation (COV) among the replicates has often been observed. Furthermore, parameters such as total fracture energy and FI do not incorporate rate dependency of fracture processes which are very important for viscoelastic materials such as asphalt mixtures at low and intermediate temperatures. In light of these observations, a rate-dependent cracking index (RDCI) is proposed that utilises cumulative fracture work potential and instantaneous power calculated from the I-FIT test to assess impulse of the mixture. Thus, in spirit, this parameter captures the fracture energy and crack velocity of the material; however, these are calculated in a rate-dependent manner. A total of 18 surface course mixtures were analysed using the RDCI and resulted in an average overall reduction of 10.6% in COV as compared to FI while maintaining similar ranking of mixtures. In general, RDCI was able to better discriminate the 18 mixtures as compared to FI. The evaluation of five mixtures at three aging levels showed the robustness of RDCI in capturing effects of aging on fracture behaviour of asphalt mixtures.]]></description>
      <pubDate>Tue, 28 May 2019 09:43:51 GMT</pubDate>
      <guid>https://trid.trb.org/View/1607344</guid>
    </item>
    <item>
      <title>Sensitivity of Life-Cycle Assessment Outcomes to Parameter Uncertainty: Implications for Material Procurement Decision-Making</title>
      <link>https://trid.trb.org/View/1582006</link>
      <description><![CDATA[This paper aims to apply an analytical approach to propagate parameter uncertainty through Life-Cycle Assessment (LCA) outcomes, and identify equivalence intervals that are applicable during material procurement decision-making. LCA outputs are usually presented as point estimates without accompanying confidence intervals, or associated margins of error, due to methodological ambiguity in accounting for uncertainties, be they epistemic (due to inherent randomness) or aleatory (due to lack of knowledge). This reduces the reliability of using LCA for design selection, and of decision-making during material procurement. This paper aims to fill this gap using a methodology based on Taylor’s first-order approximation to examine LCA outcomes for asphalt mixtures. The method is applied to assess the impact of variation in input flows on the estimated output emissions by propagating the parameter uncertainties through the LCA. It allows for the reporting of LCA outputs using intervals rather than point estimates. For competing designs, the overlap in intervals is used to construct equivalence intervals within which the effective impact of the designs can be considered equivalent due to expected variability in input parameters. The method is applied to construct equivalence intervals for the Global Warming Potential (GWP) of three asphalt mixtures, each having different levels of Reclaimed Asphalt Pavement (RAP). Their role in communicating LCA outcomes for decision-making is illustrated. Foreground data collected from 40 North American asphalt plants were used to estimate uncertainty in the input parameters of electricity and energy use in asphalt production. The paper adds to existing literature on uncertainties in pavement LCAs by establishing the need to incorporate uncertainty when using LCA to support decision-making during material procurement.]]></description>
      <pubDate>Tue, 26 Feb 2019 10:32:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/1582006</guid>
    </item>
    <item>
      <title>Impact of health differences and longitudinal changes on deceleration driving patterns in older adult drivers</title>
      <link>https://trid.trb.org/View/1581877</link>
      <description><![CDATA[Naturalistic in-car driving informatics provides opportunities to identify links between driving behaviours and cognitive and physical health status. The coefficient of variation (CoV) was used to evaluate deceleration event variability (1) for differences between 171 older adult drivers grouped based on physical and cognitive scores and (2) for changes that aligned with longitudinal health changes in 62 older adult drivers. Differences in older adult physical and cognitive health status were related to deceleration event variability. Greater deceleration event variability was identified in individuals with better cognitive health, with two exceptions. There were also deceleration events subsets where individuals with poorer physical health status exhibited greater variability in deceleration patterns than those with better health status. CoV-measured deceleration event variability did significantly decrease for individuals with longitudinal cognitive health decline and for individuals with longitudinal physical health declines (velocity signal only) for decelerations subsets and CoV increased for individuals with longitudinal physical health decline for acceleration and jerk signals for event deceleration subsets. These findings suggest that worse cognitive health may limit older adult driver’s ability to adapt deceleration patterns when needed, resulting in lower CoV-measured variability. However, particularly in situations that require less adaptation to deceleration patterns, worse physical health may induce unnecessary variability during deceleration events. Further investigation is warranted to determine whether differences in variability relate to successful braking collision avoidance behaviours.]]></description>
      <pubDate>Tue, 12 Feb 2019 16:25:05 GMT</pubDate>
      <guid>https://trid.trb.org/View/1581877</guid>
    </item>
    <item>
      <title>Probabilistic Slope Stability Analyses: Effects of the Coefficient of Variation and the Cross-Correlation of Shear Strength Parameters</title>
      <link>https://trid.trb.org/View/1557122</link>
      <description><![CDATA[The assessment of the safety level of natural slopes, road cuts, embankments and levees require consideration of uncertainties and variability in material properties. In this study, for a number of slope geometries, including a real-life landslide case, probability of failure (PF) and the most critical failure surface are investigated with and without cross-correlation of shear strength properties. Slopes having different traditionally-defined factor of safety (FS) levels are studied. The uncertainty of soil properties are considered by different levels of coefficient of variation (COV). Limit equilibrium method is used for slope stability analyses and geotechnical material properties are considered to have normal statistical distribution. The results of this analyses show that the PF and the critical failure surface is significantly influenced by the COV level, the consideration of cross correlation of shear strength parameters, and by the traditional FS level of the slopes. The inverse relation between FS and PF is demonstrated to be nonlinear and the COV level has significant effect on this relationship. Results indicate that the deterministic slope stability analyses resulting in a single FS value is no longer sufficient to evaluate the safety of a slope in geotechnical engineering, and that the deterministic critical failure surface with minimum FS value is not always the most critical slip surface. The results presented in this study could be useful for further understanding of probabilistic slope stability and the effects of soil variability/uncertainty, with the aim of better geotechnical risk evaluation and communication.]]></description>
      <pubDate>Fri, 30 Nov 2018 09:40:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/1557122</guid>
    </item>
    <item>
      <title>Number of Replicate Beams Required for a Valid Test of Asphalt Mixtures Using the Bending Beam Rheometer Based on AASHTO TP125</title>
      <link>https://trid.trb.org/View/1494995</link>
      <description><![CDATA[Developing any test, standard, or specification requires technical validity while keeping the costs as optimum as possible. AASHTO TP125 recommends Bending Beam Rheometer (BBR) as a simple, fast, relatively inexpensive, and repeatable method of testing low-temperature properties of asphalt concrete mixtures. However, a question on the number of replicate beams required to be a valid representation of population for asphalt mixture beam specimens remains unaddressed. This study used statistical methods to determine this number by analyzing the data of two variables - creep moduli and stress relaxation capacity (m-value) - obtained from testing two different asphalt concrete mixtures. It was found that BBR data follow a normal distribution with minor skewness. Moreover, by randomizing the population and taking a different number of replicate beams to analyze coefficient of variation (CV) and sample means, it was found that eight beams represent the tests results of the BBR with a CV ranging between 0.05 and 0.11, and the maximum difference between sample and population mean is below 7%. Even though testing five beams as suggested in AASHTO TP125 showed more variability in the results, still the CV was well below 0.2, and the sample mean showed more than 10% difference from the population mean. In practice, core samples of Hot Mix Asphalt (HMA) provide a limited number of replicates; therefore, testing eight beams in both field and laboratory is feasible. Results obtained from this study suggests BBR as a dependable testing equipment to characterize the low-temperature performance of asphalt concrete mixtures.]]></description>
      <pubDate>Mon, 05 Feb 2018 15:28:43 GMT</pubDate>
      <guid>https://trid.trb.org/View/1494995</guid>
    </item>
    <item>
      <title>Analysis of the Coefficient of Variation for Injection Pressure in a Compression Ignition Engine</title>
      <link>https://trid.trb.org/View/1459444</link>
      <description><![CDATA[Pressure variability in injection pipes (Pw) supplying fuel to a diesel engine cylinder was analyzed. Pressure levels were recorded at the injector nozzle. To define the variability of pressure, coefficients of variation for the injection pressure (COV sub Pw) recorded during the operation of the engine were evaluated. The results demonstrated that coefficients of variation COV sub Pw can be used to find the start of injection. Uncertainties of the results were analyzed. The test results included the data for the mineral or bio-fuel powered engine operating at full load condition within the speed range from 1000 to 2000 rpm.]]></description>
      <pubDate>Sat, 15 Apr 2017 18:45:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/1459444</guid>
    </item>
    <item>
      <title>Assessment of Uncertainty in Urban Traffic Noise Measurements</title>
      <link>https://trid.trb.org/View/1459443</link>
      <description><![CDATA[This paper presents measurement results recorded by noise and traffic volume monitoring station located in Krakowska Street, Kielce. Poland. The measurements were performed in the period from January to December 2013, twenty-four hours a day and with a sampling time of 1 minute. The results were subjected to statistical analysis. A type A uncertainty was evaluated. A new parameter COV sub LAeq was proposed for variability assessment of the equivalent sound pressure level.]]></description>
      <pubDate>Sat, 15 Apr 2017 18:45:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/1459443</guid>
    </item>
    <item>
      <title>Bayesian estimation of hazard models of airline passengers’ cancellation behavior</title>
      <link>https://trid.trb.org/View/1446620</link>
      <description><![CDATA[This study explores the use of Bayesian methods to estimate hazard models of airline passengers’ cancellation behavior. The authors show how the discrete time proportional odds (DTPO) cancellation model can be rewritten as an equivalent fixed parameter discrete choice model that can be easily estimated using Bayesian methods and extended to random parameters that account for unobserved heterogeneity. The use of Bayesian methods allows the authors to address several limitations of existing airline cancellation models. First, because of the random parameter reformulation, it is possible to calculate individual-specific cancellation probabilities. Second, unlike existing DTPO models that forecast average cancellation probabilities only, the authors' model can be used to forecast both means and a measure of variance (credible intervals) associated with an individual’s cancellation probability. The authors apply the Bayesian estimation method to a dataset of tickets purchased over a two-year period by employees of a university in Atlanta, Georgia. During this time period, the major carrier in Atlanta terminated an agreement in which it allowed employees to purchase discounted fares that could be refunded or exchanged without a fee. The data allow the authors to investigate how passenger cancellation behavior changed when these fares were discontinued. Cancellations are reduced on average 3.3% when customers must pay to exchange their tickets. For a simulated hypothetical flight the coefficient of variation of cancellation is 43% when the state rate was offered, and 83% without state rates.]]></description>
      <pubDate>Mon, 30 Jan 2017 17:15:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/1446620</guid>
    </item>
    <item>
      <title>Influence of stock shortage in integrated logistic systems: an under-estimated importance</title>
      <link>https://trid.trb.org/View/1421471</link>
      <description><![CDATA[Performance evaluation of flow systems with such indicators as 'throughput' or 'response time' shows that random delays with high dispersions degrade significantly the performances. Here the authors focus on the case of stock shortages in integrated logistic systems. These stock shortages create random delays on the component delivery and are the sources of disorders in the behaviour of the systems. The authors study the squared coefficient of variation of the random variable, a pertinent metric for evaluating the risk on the performances of the involved flows. A way to exhibit the squared coefficient of variation of the duration of the stock shortages is presented. Then, the authors consider the random variable corresponding to the potential waiting times of all the orders. This latter variable admits a squared coefficient of variation much higher than the former one. Numerical examples raise the reader awareness of the risk of under-estimating the importance of the stock shortages.]]></description>
      <pubDate>Fri, 23 Sep 2016 11:17:27 GMT</pubDate>
      <guid>https://trid.trb.org/View/1421471</guid>
    </item>
    <item>
      <title>Effect of Property Variations of Raw Materials on the Variability of Dynamic Moduli of Asphalt Mixtures</title>
      <link>https://trid.trb.org/View/1406822</link>
      <description><![CDATA[This paper presents a research on the variability of dynamic modulus of asphalt mixtures because of the variations of raw materials by error propagation theory. The coefficient of variation of dynamic module, COVE, was derived from the ?-based predictive model and the variance propagation model. Then, the raw materials' properties related to the dynamic modulus of asphalt mixture were measured and collected, and the coefficients of variation (COV) were finalized and substituted into the COVE expression. The effects of variations of raw materials' properties on the variability of dynamic module were investigated, and the efficiencies and relative efficiencies of reducing materials variability on decreasing COVE were also calculated. It is found that Va makes the greatest contributions, followed by ?4.75 and Vbeff. At high temperature the contribution of viscosity is similar to that of Vbeff, but is negligible at low temperature. However, the contributions of others are very small in all conditions. Reducing COV of ?4.75 is with the most efficiency to decrease COVE and reducing COV of Va is with the most relative efficiency. Efficiency of reducing COV of binder viscosity varies greatly with the temperature and frequency, whereas reducing COV of other parameters are much less efficient.]]></description>
      <pubDate>Thu, 26 May 2016 14:49:30 GMT</pubDate>
      <guid>https://trid.trb.org/View/1406822</guid>
    </item>
    <item>
      <title>Investigation of Testing Variables of Semicircular Bending Test for Asphalt Concrete Mixtures: Experimental-Statistical Approach</title>
      <link>https://trid.trb.org/View/1393706</link>
      <description><![CDATA[Given the fact that fracture is a primary distress resulting from pavement failure, it is important to identify and characterize the fracture/cracking properties of asphalt concrete mixtures and to include them in pavement design processes. This paper examines the testing variables of a reliable and practical semicircular bending (SCB) test for evaluating the fracture characteristics of asphalt concrete mixtures at intermediate service temperature conditions. Four testing variables (i.e., specimen thickness, notch length, loading rate, and testing temperature) of the SCB test were selected due to their significant effects on mixture fracture characteristics. Coefficient of variation (COV) of the mixture fracture energy was used to evaluate the repeatability of test results due to the variations of each testing variable. Statistical analyses were then conducted to investigate the minimum number of SCB specimens to be tested for a representative test result with the four test variables determined. A range of 0.1 mm/min. to 5 mm/min. for the loading rate, a notch length from 5 mm to 25 mm, and a SCB specimen thickness of 40 mm to 60 mm were found to result in a relatively low COV (≤10%) of the mixture fracture energy. In the range of testing temperatures attempted in this study, fracture energy at around 15° C showed the lowest testing variation. The statistical analysis of a total of 18 SCB specimens indicated that five to six SCB specimens would be a reasonable sample size that can properly represent the asphalt concrete fracture behavior of the entire population (18 specimens, in this case) with a 95% level of confidence.]]></description>
      <pubDate>Wed, 02 Mar 2016 17:12:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/1393706</guid>
    </item>
    <item>
      <title>Temporal and spatial variation in allocating annual traffic activity across an urban region and implications for air quality assessments</title>
      <link>https://trid.trb.org/View/1375630</link>
      <description><![CDATA[Patterns of traffic activity, including changes in the volume and speed of vehicles, vary over time and across urban areas and can substantially affect vehicle emissions of air pollutants. Time-resolved activity at the street scale typically is derived using temporal allocation factors (TAFs) that allow the development of emissions inventories needed to predict concentrations of traffic-related air pollutants. This study examines the spatial and temporal variation of TAFs, and characterizes prediction errors resulting from their use. Methods are presented to estimate TAFs and their spatial and temporal variability and used to analyze total, commercial and non-commercial traffic in the Detroit, Michigan, U.S. metropolitan area. The variability of total volume estimates, quantified by the coefficient of variation (COV) representing the percentage departure from expected hourly volume, was 21%, 33%, 24% and 33% for weekdays, Saturdays, Sundays and holidays, respectively. Prediction errors mostly resulted from hour-to-hour variability on weekdays and Saturdays, and from day-to-day variability on Sundays and holidays. Spatial variability was limited across the study roads, most of which were large freeways. Commercial traffic had different temporal patterns and greater variability than non-commercial vehicle traffic, e.g., the weekday variability of hourly commercial volume was 28%. The results indicate that TAFs for a metropolitan region can provide reasonably accurate estimates of hourly vehicle volume on major roads. While vehicle volume is only one of many factors that govern on-road emission rates, air quality analyses would be strengthened by incorporating information regarding the uncertainty and variability of traffic activity.]]></description>
      <pubDate>Wed, 23 Dec 2015 08:12:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/1375630</guid>
    </item>
    <item>
      <title>Quantitative X-Ray Diffraction Measurements by Fast Scanning</title>
      <link>https://trid.trb.org/View/1368030</link>
      <description><![CDATA[Two goals were pursued in this research: first, to evaluate statistically some effects of sample preparation and instrument geometry on reproducibility of X-ray diffraction intensity data; and second, to develop a procedure for finding minimum peak and background counting times for a desired level of accuracy. The ratio of calcite to dolomite in limestones was determined in trials. Ultra-fine wet grinding of the limestone in porcelain impact-type ball mill gave most consistent X-ray results, but caused considerable line broadening, and peaks were best measured on an area count basis. Sample spinning reduced variance about one-third, and a coarse beam-medium detector slit arrangement was found to be best. An equation is developed relating coefficient of variation of a count ratio to peak and background counts. By use of the equation or graphs the minimum coefficient of variation is predicted from one fast scan, and the number and optimum arrangement of additional counting periods to reduce variation to a desired limit may be obtained. The calculated coefficient is the maximum which may be attributed to the counting statistic but does not include experimental deviations.]]></description>
      <pubDate>Thu, 10 Sep 2015 15:52:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/1368030</guid>
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