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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>
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    <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>Modified Herfindahl–Hirschman Index for Measuring the Concentration Degree of Container Port Systems</title>
      <link>https://trid.trb.org/View/910890</link>
      <description><![CDATA[In the evolution of the container port system, “concentration” has been highlighted in both shipping practices and the literature. However, existing concentration measures such as the Herfindahl–Hirschman Index (HHI) cannot appropriately be used to measure the degree of concentration of port markets. This paper aims to develop a standardized index for measuring the concentration degree of container port systems on a country level. The geo-economic concentration index, a modified HHI that considers competitive interactions between ports by incorporating geographical and economic characteristics of countries, is presented. The developed index was applied to 10 selected port systems to examine how their concentration degree changed from 1975 to 2007. The results show that the modified HHI can better reflect the concentration degree of port systems than the conventional HHI.]]></description>
      <pubDate>Wed, 14 Apr 2010 07:14:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/910890</guid>
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      <title>SOME CONSIDERATIONS OF VEHICULAR DENSITY ON URBAN FREEWAYS</title>
      <link>https://trid.trb.org/View/116542</link>
      <description><![CDATA[VEHICULAR DENSITY STUDIES WERE MADE ON THE GULF FREEWAY IN HOUSTON, TEXAS. CONGESTION IS A QUALITATIVE TERM USED IN TRAFFIC ENGINEERING TO INDICATE A CONDITION OF TRAFFIC AND TRAFFIC MOVEMENT. DENSITY IS THE QUANTITATIVE MEASURE OF CONGESTION AND IS, THEREFORE, THE MOST DESIRABLE ELEMENT TO USE IN FREEWAY OPERATION CONTROL. THE PRINCIPAL FEATURES OF EXISTING METHODS USED TO MEASURE OR ESTIMATE DENSITY ARE REVIEWED. A PROCESS IN WHICH DENSITY IS ESTIMATED ON THE BASIS OF SPEEDS AND VOLUMES SENSED AT A POINT IS COMPARED TO A METHOD INVOLVING THE ACTUAL MEASUREMENT OF THE DENSITY, OR CONCENTRATION OF VEHICLES IN A SPACE. AERIAL PHOTOGRAPHY STUDIES ARE PRESENTED TO SHOW HOW DENSITY MAY BE RELATED TO VOLUME AS WELL AS TO CERTAIN GEOMETRIC FEATURES OF THE FREEWAY FACILITY. A FIELD STUDY METHOD IS DESCRIBED WHICH YIELDS CONTINUOUS VALUES OF VEHICULAR CONCENTRATION ON CERTAIN SECTIONS OF A FREEWAY. THE ANALYSIS OF THE DATA DEMONSTRATES A MEANS OF ESTABLISHING OPTIMUM, OR CRITICAL, FREEWAY CONCENTRATION VALUES AND PROVIDES A MEANS OF IDENTIFYING CRITICAL, OR BOTTLENECK, SECTIONS AT A FREEWAY WHICH EXHIBIT RECURRING HIGH DENSITIES.]]></description>
      <pubDate>Mon, 12 Dec 1994 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/116542</guid>
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      <title>RAPID ESTIMATION OF CHLORIDE DIFFUSION COEFFICIENT IN CONCRETE</title>
      <link>https://trid.trb.org/View/366550</link>
      <description><![CDATA[A simple potential difference (PD) test is developed that can rapidly (within about 10 days) provide a chloride diffusion index.  The test utilizes a small applied potential difference (10 V dc) to accelerate the transport of chloride ions through concrete.  Conventional non-perturbative, concentration difference (CD) tests have been carried out in parallel, with typical test periods of up to 12 months.  Fick's First Law of Diffusion is applied to calculate a diffusion index from the PD test, and the coefficient of chloride diffusion D from the CD test.  A close relationship between these two parameters is shown, allowing D to be estimated from rapid PD test. (Author/TRRL) (Author/TRRL)]]></description>
      <pubDate>Fri, 31 Jul 1992 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/366550</guid>
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    <item>
      <title>CALINE-2 COMPUTER PROGRAM MODEL SIMULATION</title>
      <link>https://trid.trb.org/View/58634</link>
      <description><![CDATA[CALINE-2 is a Gaussian line source air pollution dispersion model for estimating concentrations of carbon monoxide downwind from roadways. The computational algorithms in the CALINE-2 model are extracted and assembled in a series of subroutines contained in a controlling subroutine called CAL 2. CAL 2 does not contain any provision for input/output other than as subroutine arguments. The following items are contained on a single file on this tape: (1) CALINE-2 Fortran source program; (2) sample input data (42 test problems); (3) subroutine CAL 2 Fortran source program. Details of the theory and development of CALINE-2 are contained in the report FHWA-RD-77-74, 'CALINE-2: An Improved Microscale Model for the Dispersion of Air Pollutants from a Line Source'. This report should be available from NTIS in September/October 1977...Software Description: This model is written in the Fortran programming language for implementation on an IBM 360/65 computer using the OS/REL operating system. 40K bytes of core storage are required to operate this model.]]></description>
      <pubDate>Sun, 29 Oct 1978 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/58634</guid>
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    <item>
      <title>USE OF CONCENTRATION INDEX FOR PAVEMENT DESIGN</title>
      <link>https://trid.trb.org/View/140623</link>
      <description><![CDATA[The application of the concentration index to pavements is illustrated.  The problem with the design of flexible airfield pavements under newly developed jumbo-jet aircraft, as represented by the Lockheed C-5A Galaxy and the Boeing 747, is examined.  These aircraft are equipped with extremely large multiple-wheel landing gears.  It is found that the CBR design equation can be used to evaluate the pavement performance under multiple-wheel gear assemblies when the equivalent single-wheel load (ESWL) is computed by the concentration index method.  The concentration index is approximately independent of the load, gear configuration, and soil strength but varies with the depth.]]></description>
      <pubDate>Tue, 11 Feb 1975 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/140623</guid>
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    <item>
      <title>SENSORY MEASUREMENT OF AMBIENT TRAFFIC ODORS</title>
      <link>https://trid.trb.org/View/132582</link>
      <description><![CDATA[LABORATORY DETERMINATIONS OF AMBIENT TRAFFIC ODORS WERE CONDUCTED IN THE STREETS OF STOCKHOLM.  THE MEASUREMENTS WERE MADE WITH A SENSORY METHOD BASED ON SIGNAL DETECTION THEORY.  THE OCCURRENCE OF ODORS WAS EXPRESSED BY AN INDEX OF DETECTABILITY WHICH WAS COMPARED TO THE AMBIENT CARBON MONOXIDE CONCENTRATION AND THE RHYTHM OF THE TRAFFIC.  THE RESULTS SHOWED THAT THE DETECTION TECHNIQUE EMPLOYED COULD WELL BE ADJUSTED TO FIELD CONDITIONS BY USE OF A MOBILE ODOR LABORATORY.  ALSO, THE ODOR INDEX WAS CORRELATED WITH OTHER PARAMETERS IN THE TRAFFICKED ENVIRONMENT IN THE EXPECTED WAY.  /DOT/]]></description>
      <pubDate>Wed, 24 Oct 1973 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/132582</guid>
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