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    <title>Transport Research International Documentation (TRID)</title>
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    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
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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>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>Empirical Investigation of the Validity of the Traffic Network Equilibrium Paradigm</title>
      <link>https://trid.trb.org/View/1106018</link>
      <description><![CDATA[This paper will discuss network equilibrium models and that for many decades been the mainstay of transport planning. Developments to these models, to incorporate uncertain or time-dependent factors, have not changed the underlying principles. It is contended that, of the thousands of practical applications of such models, virtually none truly test the validity of the underlying hypotheses. Typically, data collection efforts are focused on origin-destination flows, travel time functions and valuation parameters, but calibration focuses only on reproducing current, observed conditions. No test is made about the plausibility of how the model responds to change, yet its key planning role is in predicting performance of future networks under hypothetical conditions. Only a handful of studies have been published which compare real before-and-after effects of a scheme with the predictions of a network equilibrium model, and in those cases only quite crude comparisons are made, e.g. of link flows. This paper reports the findings of a completed study, which aimed to explore how a real network adapted to change. Primary data consist of a time-series of observations covering the morning peak period over some twelve weekdays, before, during and after a real network change (capacity reduction). Observations were made of time-stamped (partial) registration plates across twelve sites. Matching together these data reveals information on sequences of observation stations passed, providing path-like information, and the distribution of point-to-point journey times both within and between days.]]></description>
      <pubDate>Wed, 20 Jul 2011 07:24:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/1106018</guid>
    </item>
    <item>
      <title>Exploring time variants for short-term passenger flow</title>
      <link>https://trid.trb.org/View/1105235</link>
      <description><![CDATA[Passenger flow is a fundamental element in a transportation system. It is important to explore the time variants of short-term passenger flow for transportation planning and operation. When the data are sufficiently analyzed, transportation planners not only can make better decisions, but also enhance the performance of transportation systems. The data of short-term passenger flow may be difficult to analyze due to its exotic oscillation. Hilbert-Huang transform (HHT) has recently been developed for analyzing non-linear and non-stationary data. In this paper, the proposed time variants exploration method includes two stages: empirical mode decomposition (EMD) and Hilbert spectral analysis. A real passenger flow dataset is collected from Taipei rapid transit corporation to investigate the viability of the proposed time variants exploration approach. The intrinsic mode functions extracted by EMD can represent the local characteristics of passenger flow and imply its meaningful time variants such as peak period pattern, semi-service period pattern, semi-daily pattern and daily pattern. By comparing the results of HHT with that of fast Fourier transform, it indicates that HHT can obtain the narrower frequency band, accurately capture time-frequency-energy distribution, and help to enhance the performance of transportation systems. The results show that HHT is an effective approach for exploring the time variants of short-term passenger flow in a metro system.]]></description>
      <pubDate>Wed, 20 Jul 2011 07:23:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/1105235</guid>
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    <item>
      <title>Laboratory Performance Evaluation of CIR-emulsion and Its Comparison against CIR-foam Test Results from Phase II</title>
      <link>https://trid.trb.org/View/915772</link>
      <description><![CDATA[Currently, no standard mix design procedure is available for cold in-place recycling (CIR)-emulsion in Iowa. The CIR-foam mix design process developed during the previous phase is applied for CIR-emulsion mixtures with varying emulsified asphalt contents. Dynamic modulus test, dynamic creep test, static creep test and raveling test were conducted to evaluate the short- and long-term performance of CIR-emulsion mixtures at various testing temperatures and loading conditions. A potential benefit of this research is a better understanding of CIR-emulsion material properties in comparison with those of CIR-foam material that would allow for the selection of the most appropriate CIR technology and the type and amount of the optimum stabilization material. Dynamic modulus, flow number and flow time of CIR-emulsion mixtures using CSS-1h were generally higher than those of HFMS-2p. Flow number and flow time of CIR-emulsion using recycled asphalt pavement (RAP) materials from Story County was higher than those from Clayton County. Flow number and flow time of CIR-emulsion with 0.5% emulsified asphalt was higher than CIR-emulsion with 1.0% or 1.5%. Raveling loss of CIR-emulsion with 1.5% emulsified was significantly less than those with 0.5% and 1.0%. Test results in terms of dynamic modulus, flow number, flow time and raveling loss of CIR-foam mixtures are generally better than those of CIR-emulsion mixtures. Given the limited RAP sources used for this study, it is recommended that the CIR-emulsion mix design procedure should be validated against several RAP sources and emulsion types.]]></description>
      <pubDate>Thu, 08 Apr 2010 16:29:57 GMT</pubDate>
      <guid>https://trid.trb.org/View/915772</guid>
    </item>
    <item>
      <title>Production Scheduling and Truck Dispatching of Ready Mixed Concrete</title>
      <link>https://trid.trb.org/View/842513</link>
      <description><![CDATA[In this research, the authors develop an integrated model that combines ready mixed concrete (RMC) production scheduling and truck dispatching in the same framework. The model is formulated as a mixed integer network flow problem with side constraints, which is characterized as NP-hard. To solve realistic problems, the authors develop a solution method, which incorporates a mathematical programming solver. To evaluate the model and the solution method, numerical tests using real operating data from an RMC firm in Taiwan are performed. The test results show that the model and the solution algorithm would be useful for actual operations.]]></description>
      <pubDate>Mon, 28 Jan 2008 08:09:38 GMT</pubDate>
      <guid>https://trid.trb.org/View/842513</guid>
    </item>
    <item>
      <title>Specification Criteria for Simple Performance Tests for Rutting: Volume I: Dynamic Modulus (E*) and Volume II: Flow Number and Flow Time</title>
      <link>https://trid.trb.org/View/844079</link>
      <description><![CDATA[This report summarizes in two volumes key information on three recommended simple performance tests for permanent deformation (rutting) of hot mix asphalt (HMA).  In the final phase of the work described here, the candidate tests for permanent deformation were validated with field performance data and specifications for their use were developed.  The report will be of particular interest to materials engineers in state highway agencies, as well as to materials suppliers and paving contractor personnel responsible for designing and producing HMA mixes.]]></description>
      <pubDate>Fri, 11 Jan 2008 14:56:59 GMT</pubDate>
      <guid>https://trid.trb.org/View/844079</guid>
    </item>
    <item>
      <title>Efficient Evaluation of the Measure of Effectiveness of the Lighthill-Whitham-Richards Traffic Flow Model on a Homogeneous Highway</title>
      <link>https://trid.trb.org/View/801016</link>
      <description><![CDATA[In this paper, we discuss the efficient evaluation of the measure of effectiveness of the analytical shock-fitting algorithm that was developed to solve the well-known Lighthill-Whitham-Richards traffic flow model when it is embedded with a linear speed-density relationship or parabolic fundamental diagram. We develop explicit expressions to calculate the measure of effectiveness – which is the travel time that is incurred by travelers, within the space-time region that is encompassed by the shocks and/or characteristic lines. A numerical example is used to illustrate the effectiveness and efficiency of the proposed method compared to the numerical solutions that are obtained by a fifth-order weighted essentially non-oscillatory scheme.]]></description>
      <pubDate>Wed, 09 May 2007 07:47:01 GMT</pubDate>
      <guid>https://trid.trb.org/View/801016</guid>
    </item>
    <item>
      <title>Characterization of Louisiana Asphalt Mixtures Using Simple Performance Tests</title>
      <link>https://trid.trb.org/View/802298</link>
      <description><![CDATA[The main objective of this study was to characterize the performance of HMA mixes based on four laboratory tests, including three simple performance tests (SPTs) dynamic modulus |E*|, flow time (Ft), flow number (FN), and a loaded wheel tracking test (LWT). In addition, two dynamic modulus prediction models, namely Witczak and Hirsch, were evaluated.  Thirteen plant-produced HMA mixtures were selected in this study. Laboratory characterization tests included the dynamic modulus |E*|, flow number (FN), and Hamburg-type wheel tracking tests. Test results indicated that the |E*| test was sensitive to the nominal maximum aggregate size (NMAS) in HMA mixture.  Larger aggregates combined with recycled asphalt (RAP) tended to have high |E*| values at high temperatures. Both the Witczak and Hirsch models could predict the dynamic modulus |E*| values with a reasonable reliability. However the Witczak model reliability increases for higher NMAS. On the other hand the Hirsch model reliability increases for lower NMAS. The general ranking of the SPTs and LWT test was similar.  In addition, this ranking was consistent with the field use of those mixtures in terms of their design traffic volume.]]></description>
      <pubDate>Wed, 21 Mar 2007 12:46:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/802298</guid>
    </item>
    <item>
      <title>Simple Performance Test for Moisture Damage Prediction in Asphalt Concrete (With Discussion)</title>
      <link>https://trid.trb.org/View/798213</link>
      <description><![CDATA[Developing a highly reliable laboratory test to predict the susceptibility of hot mix asphalt (HMA) concrete to moisture damage remains a challenge to asphalt industry. Pennsylvania State University in cooperation with Advanced Asphalt Technologies, LLC, University of Texas at El Paso, and PaveTex Engineering and Testing, Inc. conducted an extensive research study to develop an improved testing procedure for prediction of moisture damage in HMA. The research, sponsored by National Cooperative Highway Research Program (NCHRP) was conducted in two phases and included eleven different mixes from various states with known field performance. The simple performance tests, developed by NCHRP projects 9-19 and 9-29, were utilized with the Environmental Conditioning System (ECS) and the combined system was used to test moisture damage sensitivity of these mixes. Phase I included the design and execution of an experiment where unconditioned and ECS conditioned specimens were tested using the three Project 9-19 simple performance tests: flow time, flow number, and dynamic modulus. Tests were conducted on three mixtures made from aggregates with good, marginal, and poor resistance to moisture damage based on past research. In addition to the combined ECS/simple performance tests, ASTM D4867 and the Hamburg Wheel Tracking Device were included in the Phase I experiment. The primary conclusion from the Phase I experiment was that the dynamic modulus test was the most suited of the three simple performance tests for possible use with the ECS in an improved moisture sensitivity test. Phase II included eight mixtures with known field performance in regard to moisture damage. Three were good performing mixes and five were poor performing. These mixes were tested with the combined ECS/dynamic modulus system. The mixes were also tested according to ASTM D4867 and the Hamburg Wheel Tracking Device. The results indicated that the dynamic modulus test utilized with the ECS has the potential to discriminate between good and poor performing mixes in regard to stripping and moisture damage.]]></description>
      <pubDate>Tue, 30 Jan 2007 13:29:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/798213</guid>
    </item>
    <item>
      <title>Selection of Optimum Gravel Aggregate Size to Resist Permanent Deformation in Hot-Mix Asphalt</title>
      <link>https://trid.trb.org/View/777354</link>
      <description><![CDATA[Siliceous river gravels form a significant fraction of the different types of aggregates used in the construction of hot-mix asphalt (HMA) pavements. Even after gravel particles are crushed into smaller-size fractions, a significant proportion of the larger-size fractions retain their original shape and surface texture. As a result, HMA with a larger nominal maximum aggregate size (NMAS) has a higher percentage of rounded and low-angularity particles, which might make it more susceptible to rutting. Using a smaller NMAS may decrease the percentage of rounded and angular aggregates in the mix, but potentially at the expense of loss in shear strength of the mix. This study evaluated the effect of increasing aggregate angularity by decreasing NMAS on the rutting potential of HMA mixes containing siliceous gravels. Nine mix designs composed of three different NMASs and siliceous aggregates from three different sources were included in this study. The percentage of rounded and angular aggregates in each mix was quantified using image analysis and crushed-face count. The rutting potential of HMA mixes was assessed on the basis of Hamburg, dynamic modulus, flow time, and flow number tests. Results verify that a decrease in NMAS results in a decrease in the percentage of rounded and angular aggregates. However, rutting performance improves initially with a decrease in NMAS but then decreases; this indicates an optimum size that maximizes the rut resistance of HMA with siliceous aggregates. Results from this study are especially useful in selecting an optimum aggregate size for HMA mixes in locations where river gravels are the main source of locally available aggregates.]]></description>
      <pubDate>Thu, 29 Jun 2006 07:39:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/777354</guid>
    </item>
    <item>
      <title>Appendixes to NCHRP Report 547: Simple Performance Tests and Advanced Materials Characterization Models</title>
      <link>https://trid.trb.org/View/783228</link>
      <description><![CDATA[These appendixes to NCHRP Report 547, "Simple Performance Tests:  Summary of Recommended Methods and Database," contain the following:  (1) All test data, mixture data, master curves, and master curve parameters obtained from the dynamic modulus (E*) testing and analysis; (2) All test and mixture data obtained from the flow number and flow time tests, including the permanent strain at flow, recoverable strain at flow, permanent strain at flow/recoverable strain at flow, and compliance; and (3) A collection of technical reports, theses and dissertations, and other relevant documents prepared during the course of NCHRP Project 9-19 and its predecessor FHWA project to support the development of the simple performance tests.]]></description>
      <pubDate>Thu, 22 Jun 2006 15:46:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/783228</guid>
    </item>
    <item>
      <title>A Practical Look at the Simple Performance Tests: Louisiana's Experience (With Discussion)</title>
      <link>https://trid.trb.org/View/776094</link>
      <description><![CDATA[The Superpave volumetric mix design procedure developed during the Asphalt Research Program of the Strategic Highway Research Program did not include a mechanical “proof” test similar to the ones commonly used in the Marshall mix design or Hveem mix design such as the Marshall stability and flow tests or the Hveem stabilometer method, respectively. The Superpave mix design method, however, did use strict requirement to material specifications and volumetric mix criteria to ensure satisfactory performance of mix designs that were intended for low volume traffic. In addition, the original Superpave mix design protocol required mix verification for intermediate and high volume traffic through advanced materials characterizations tests utilizing the Superpave Shear Tester test protocols. It was quickly recognized the complexity of those test protocols for routine mix design application and that a simple performance test is needed to complement the Superpave volumetric mix design procedure. In response to this need, National Cooperative Highway Research Program (NCHRP) Project 9-19, Superpave Support and Performance Models Management, recently recommended three candidate Simple Performance Tests (SPTs) to complement the Superpave volumetric mixture design method. These are flow time (FT), flow number (FN), and dynamic modulus |E*| tests. In addition, the dynamic modulus test was selected for the hot mix asphalt (HMA) materials characterization input utilized in the 2002 Empirical and Mechanistic Guide for Design of New and Rehabilitated Pavement Structures, developed under NCHRP Project 1-37A. This paper presents a practical look at the results of a cooperative evaluation of similar Superpave mixtures utilizing two tests of the SPTs: the Dynamic Modulus and Flow Number. Two different dynamic modulus predictive models, Witczak and Hirsch, were also evaluated.]]></description>
      <pubDate>Mon, 27 Mar 2006 11:07:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/776094</guid>
    </item>
    <item>
      <title>RESULTS OF INTEGRATING SIMPLE PERFORMANCE TESTS AND ENVIRONMENTAL CONDITIONING SYSTEM</title>
      <link>https://trid.trb.org/View/747464</link>
      <description><![CDATA[Under the guidance of the Strategic Highway Research Program, an environmental conditioning system (ECS) was developed to simulate field conditions to identify the moisture sensitivity of asphalt concrete mixes.  However, the system was not included in Superpave because of poor repeatability.  Studies conducted at the University of Texas at El Paso improved the prediction capabilities of the conditioning system.  The modified system uses resilient modulus as a moisture sensitivity indicator. Resilient modulus has been commonly used by highway practitioners as an indicator of hot-mix asphalt concrete performance.  However, as an extension to the Superpave system, under NCHRP Project 9-19, researchers have proposed simple tests to evaluate the performance of asphalt concrete.  These tests are referred to as dynamic modulus, flow number, and flow time.  The objective of this study was to evaluate the potential of these tests, when integrated with an ECS, to predict moisture damage in lieu of the resilient modulus.  Three mixes of known performance were selected and conditioned by using a conditioning procedure of the modified system.  The simple performance tests were done on unconditioned as well as ECS-conditioned specimens.  The integration results indicate that the flow number and flow time tests, as conducted during this study, do not have the potential to replace resilient modulus in ECS for identification of moisture-susceptible asphalt concrete in the present form.  However, the dynamic modulus test demonstrated their potential as a performance indicator replacing the resilient modulus test.  The results of the integration efforts are presented here.]]></description>
      <pubDate>Tue, 18 Jan 2005 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/747464</guid>
    </item>
    <item>
      <title>EVALUATION OF SIMPLE PERFORMANCE TESTS ON HOT-MIX ASPHALT MIXTURES FROM SOUTH CENTRAL UNITED STATES</title>
      <link>https://trid.trb.org/View/747467</link>
      <description><![CDATA[Since development of the Superpave mix design procedure under the Strategic Highway Research Program about a decade ago, there has been a need to develop some type of a simple physical test to complement the Level 1 volumetric mixture design procedure. NCHRP Project 9-19 recognized the dynamic modulus test along with the flow time and flow number tests as the top three candidates for a simple performance test that could identify mixtures susceptible to permanent deformation.  A critical evaluation of these three tests is presented along with the Superpave shear test-frequency sweep at constant height with the asphalt pavement analyzer (APA) as the torture test to identify mixes susceptible to permanent deformation.  The Hamburg wheel-tracking device (HWTD) also was used on selected mixtures. Special laboratory hot-mix asphalt mixes designed to exhibit low dynamic modulus but high recovery of strains were included in this evaluation.  Results indicated that flow number value and flow time slope correlated better with laboratory rutting (APA and HWTD) than dynamic modulus.  Flow number value, flow time slope, E*/sin phi at 1 Hz, flow number slope, and flow time value were among the best five correlations with both the APA and the HWTD rut depths.]]></description>
      <pubDate>Tue, 18 Jan 2005 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/747467</guid>
    </item>
    <item>
      <title>CAPILLARY FLOW IN THE GEOTECHNICAL CENTRIFUGE</title>
      <link>https://trid.trb.org/View/512905</link>
      <description><![CDATA[A "bundle of capillaries" approach is used to model unsaturated soils. Movement of fluid is approximated by employing a simple Poiseuille's capillary flow mathematical model. It is found that the centrifuge model flow time is 1/n-squared. times that for the pertinent prototype flow time. Here model acceleration = n X acceleration of gravity (i.e., a = ng). This result applies for: 1) capillary rise at an arbitrary angle to the horizontal, 2) horizontal capillary flow, 3) downward capillary flow (infiltration) at an arbitrary angle, and 4) vertical drainage at an arbitrary angle. This is the same centrifuge model scale factor as for advection, diffusion, and dispersion.]]></description>
      <pubDate>Mon, 13 Dec 1999 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/512905</guid>
    </item>
    <item>
      <title>PROPERTIES OF HIGH-STRENGTH AND HIGH-FLUIDITY LIGHTWEIGHT CONCRETE</title>
      <link>https://trid.trb.org/View/539149</link>
      <description><![CDATA[High-strength and high-fluidity lightweight concretes have been developed using silica fume blended cement and belite-rich cement with a designed compressive strength from 40 to 60 MPa. Test conditions and parameters were water-cement ratio of 0.22, 0.33 and 0.40, curing temperature of 5, 20 and 35 deg C, curing method of standard and sealed curing and 3 types of high-range AE water-reducing agent.  Influences of above factors upon flow, flow time, compressive strength, permeability, pore size distribution and total pore volume were studied.  The major findings of this study are as follows:  (1) Compressive strength of silica fume blended cement concrete was higher than that of belite-rich cement concrete and the effect of water-cement ratio was small.  Compressive strength at 7 days was 80 to 90% of the 28-day strength at any curing temperature.  (2) Compressive strength of belite-rich cement concrete significantly increased at water-cement ratio of 0.3 to 0.4, and its evolution from 28 to 91 days became larger at lower curing temperatures.  (3) Total pore volume of silica fume blended cement concrete at the age of 28 days was smaller than that of belite-rich cement concrete at all curing temperatures of 5, 20 and 35 deg C, and compressive strength became larger with a decrease of total pore volume.]]></description>
      <pubDate>Fri, 11 Sep 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/539149</guid>
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