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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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      <link>https://trid.trb.org/</link>
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    <item>
      <title>LESSONS LEARNED IN 25 YEARS OF ENGINEERING MARTA'S AERIAL STRUCTURES</title>
      <link>https://trid.trb.org/View/485771</link>
      <description><![CDATA[In 1972, the Metropolitan Atlanta Rapid Transit Authority (MARTA) started design of a rail transit system for the Atlanta Area.  25 years later, the system consists of 45 miles (72 km) of rail lines and 36 stations.  The rail line contains approximately 8 miles (12.8 km) of tunnels.  The system is still expanding, with the extension of the North line another 2 miles (3.2 km) and the addition of 2 more stations at Sandy Springs and North Springs scheduled for revenue service in late 2000.  Many improvements over the years have been made to MARTA's steel and concrete aerial structures in an effort to improve performance and minimize maintenance. Some specific examples of the improvements: Improved deck drainage details; improved superstructure anchor bolt and tie-down details; improved elastometric bearing design and provision for easy bearing replacement; elimination of expansion joints through use of continuous structures; better access to the interior of box girders; and, development of a standard AASHTO Girder arterial design.]]></description>
      <pubDate>Sat, 23 May 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/485771</guid>
    </item>
    <item>
      <title>RAIL ISOLATION ON THE BALTIMORE CENTRAL LIGHT RAIL LINE</title>
      <link>https://trid.trb.org/View/382745</link>
      <description><![CDATA[Construction designs for modern DC transit systems include the concept of "source control" to eliminate or minimize the generation of stray currents. This article presents rail insulation methods designed for embedded track, aerial sections, concrete ties, and wood ties used at special track-work sections. Some of the construction problems encountered and their solutions are discussed.]]></description>
      <pubDate>Fri, 08 Oct 1993 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/382745</guid>
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    <item>
      <title>AERIAL STRUCTURE NOISE REDUCTION EFFECTIVENESS OF RESILIENT RAIL FASTENERS</title>
      <link>https://trid.trb.org/View/309039</link>
      <description><![CDATA[Resilient rail fasteners have received significant attention at the New York City Transit Authority (NYCTA) and the Washington Metropolitan Area Transit Authority (WMATA) as a means for reducing wayside noise from steel stringer and steel box elevated structures and groundborne noise from subways.  Noise and vibration data collected at NYCTA and WMATA indicate that noise and vibration reductions are generally small unless very soft resilient fasteners are used.  Very soft fasteners providing good low-frequency performance may exhibit poor isolation or amplify structure vibration at frequencies above 200 to 400 Hz because of resonances in the elastomer pad or top plate.  Laboratory tests of the forward transfer impedance of resilient rail fasteners indicate that these secondary resonance frequencies are about 600 to 800 Hz for the softest fasteners tested for the NYCTA and WMATA systems.  A laboratory test procedure has been developed into an acceptance test procedure for resilient fasteners supplied to the WMATA system as noise-reducing fasteners for either subway or elevated structure use.  This procedure represents a substantial change in acceptance test procedures that have heretofore focused on physical properties related to stability and safety of the fasteners.  Data are presented illustrating measured noise reductions and laboratory test results.]]></description>
      <pubDate>Tue, 31 Jul 1990 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/309039</guid>
    </item>
    <item>
      <title>CONTINUOUS-WELDED RAIL ON BART AERIAL STRUCTURES</title>
      <link>https://trid.trb.org/View/288430</link>
      <description><![CDATA[A review and description are presented of the design approach and development of materials needed to directly attach continuous-welded rail (CWR) to prestressed concrete aerial structures on the San Francisco Bay Area Rapid Transit (BART) Project. The methods used to calculate the interaction forces and movements between the CWR and aerial structure are defined and the results are illustrated. Special designs for track crossovers and anchor abutments are described. BART's construction of 24 route miles of aerial track was the first large-scale installation of CWR directly affixed to concrete girders in North America. The design concepts and hardware developed for BART established a basis for the design of all subsequent new transit projects.]]></description>
      <pubDate>Sat, 31 Oct 1987 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/288430</guid>
    </item>
    <item>
      <title>SEGMENTAL AERIAL STRUCTURES FOR ATLANTA'S RAIL TRANSIT SYSTEM</title>
      <link>https://trid.trb.org/View/288429</link>
      <description><![CDATA[The typical superstructure of the aerial structure of the Metropolitan Atlanta Rapid Transit Authority (MARTA) rail transit system is a rectangular box girder supporting a concrete deck for the two parallel tracks. Alternative designs permit a steel box girder with either a precast or cast-in-place deck or a monolithic girder and deck of cast-in-place concrete. Segmental construction of the monolithic superstructure is permitted. Precast monolithic superstructure is not practical, however, because of highway load limits. On two separate projects constructed from 1982 to 1984, the contractor elected to build the monolithic superstructure by the segmental method and gained approval for a value engineering proposal to change the girder cross section from rectangular to trapezoidal and to increase its width and depth. One of the projects (on MARTA's South Line) included 65 spans with a total superstructure length of 5,231 ft and the other project (on MARTA's North Line) included 20 spans with a total length of 1,880 ft. Some property that had been acquired for the proposed parking lot for MARTA's Oakland City Station afforded the contractor a convenient site for a casting yard (within 1 mi of the centroid of the South Line aerial structure). Although the same yard was used for casting segments for the North Line aerial structure, those segments had to be hauled more than 10 mi to the erection site. The completed structures have been in service since late 1984 and represent what is believed to be the first employment of segmental construction methods for rail transit aerial structures in the United States.]]></description>
      <pubDate>Sat, 31 Oct 1987 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/288429</guid>
    </item>
    <item>
      <title>ASSESSMENT OF VISUAL IMPACTS OF AGT GUIDEWAYS</title>
      <link>https://trid.trb.org/View/210722</link>
      <description><![CDATA[Public reaction to alternative transit guideway design characteristics and impact on the existing environment can be assessed by formal surveys employing a series of photomontages depicting random views of design options. Simulations showing possible alinements, column spacings, guideway heights, and architectural styles as well as other design variables can be evaluated by means of a simple preference scale, and preferences compared among population groups having potentially different interests in the guideway.  Scaling techniques and analysis of variance are used to determine relative preferences for alternative designs and differences in preference among interest groups.  A study in Morgantown, West Virgina, for a hypothetical extension of the Morgantown Downtown People Mover, indicated that people preferred a sidewalk location with slim columns, and found that a guideway reduced the overall visual quality of the environment.  However, the environment without the guideway was perceived as neutral or slightly unattractive to begin with.  The general public and economic interest groups were less critical of the impact of the guideway than persons with esthetic training.]]></description>
      <pubDate>Fri, 29 Mar 1985 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/210722</guid>
    </item>
    <item>
      <title>BALLASTLESS TRACK: A RAPID TRANSIT WAVE OF THE FUTURE?</title>
      <link>https://trid.trb.org/View/203785</link>
      <description><![CDATA[Successful application of ballastless track carried directly on concrete substructures is relatively new but gaining in popularity because it will retain its geometry longer than ballasted track.  In tunnels it will also minimize bore size and on bridges will reduce dead weight.  Three general types of ballastless track are used; Group I, the block system, in which rail is supported on prefabricated blocks set in a trackbed of longitudinal troughs; Group II, direct fixation on supporting structure, where the rail is mounted on bearing plates and elastomeric pads set directly on the bridge deck or tunnel invert; Group III, paved or slab track, where the supporting slab is poured in one pass to final alignment. All three designs have advantages but Group I appears to be the most versatile and easiest to construct.  For bridges, rail expansion joints have traditionally been placed at each pier, and span lengths limited.  For Miami Metro, it was decided to utilize long aerial structures of increased span length, then utilize rail fasteners where creep resistance could be limited.  This would control effects of differential expansion of structure and rail. Although ballastless track is widely accepted for rapid transit, much development remains.  Design criteria are still empirical; noise and vibration damping require development; and turnouts and at-grade construction need to be researched.]]></description>
      <pubDate>Thu, 28 Jun 1984 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/203785</guid>
    </item>
    <item>
      <title>AERIAL STRUCTURE AND RAIL SUPPORT METHODS REPORT NO 11</title>
      <link>https://trid.trb.org/View/11040</link>
      <description><![CDATA[A series of tests was run for BART to evaluate the ability of rail fasteners to maintain electrical isolation, reduce noise levels, and provide safety and economy; and to determine their suitability for use on advanced design concrete aerial structures.  The evaluation of several types of concrete ties and the results of tests on a new concept in the installation of rail fasteners and associated hardware on concrete aerial structures are included. Investigation showed that a new concept of track support was required for aerial structures and subways; further, it was realized that the fastener chosen for use on the aerial structures can also be used on the underground portions of the rapid transit system, a fact which will limit the types of rail fasteners needed for the system. Subsequent studies, therefore, are geared to the choice of a fastener suitable for use on aerial structures.  On aerial structures rail fasteners must be simple enough for one man to assemble with hand-carried tools.  The fastener must remain stable under the application of a 15,000-pound wheel load and must be capable of holding a longitudinal force of approximately 2,000 pounds of 3,000,000 cycles of loading in a test machine.  Other criteria for fasteners of rail and aerial structures are listed.  The "second pour" technique, which still requires further development, is to be used in installing track fasteners on concrete surfaces in order to guarantee that the anchor bolts will not come in direct contact with reinforcing steel.  Indications from test results indicate that concrete ties are safe and economical and perform well under the type of transit loadings expected in the BARTD system.]]></description>
      <pubDate>Tue, 24 Aug 1982 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/11040</guid>
    </item>
    <item>
      <title>SUBSURFACE INVESTIGATION, SECTION A013, ROCKVILLE ROUTE</title>
      <link>https://trid.trb.org/View/23909</link>
      <description><![CDATA[Results are summarized of 65 test borings made at the locations of aerial structure piers and cut-and-cover construction in Section A013 of Rockville Route, generally following Rockville Pike north of the Capital Beltway in Montgomery County, Maryland, of the Washington Metropolitan Area Metro system. The report includes a continuous geological section along the centerline of the METRO structures through the test borings, logs of these borings, results of laboratory tests on soil samples and comments on potential design and construction problems.]]></description>
      <pubDate>Fri, 26 Jun 1981 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/23909</guid>
    </item>
    <item>
      <title>ELEVATED STRUCTURE FOR ATLANTA TRANSIT SYSTEM:</title>
      <link>https://trid.trb.org/View/52062</link>
      <description><![CDATA[A standardized elevated structure for above-ground segments of the Metropolitan Atlanta Rapid Transit system was designed primarily for installation with adequate clearance on railroad rights-of-way and also as a low-profile aerial guideway which would be aesthetically suitable in residential neighborhoods.  The concept involves a prestressed concrete deck slab acting compositely with single box girders supported on rectangular concrete columns.  Various sound-deadening arrangements have been part of the structural design.]]></description>
      <pubDate>Sun, 31 May 1981 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/52062</guid>
    </item>
    <item>
      <title>STATIC THREE DIMENSIONAL ANALYSIS OF ELEVATED STEEL TRANSPORTATION STRUCTURES</title>
      <link>https://trid.trb.org/View/23698</link>
      <description><![CDATA[A three-dimensional finite element modeling technique that may be used to statistically analyze many classes of steel elevated transportation structures for design, analysis, and maintenance studies was developed and tested. Parameter studies on a typical class of steel elevated transit structure found in many cities showed that: (1) a 50 foot long built-up plate girder representation modeled as 50 beam elements and 100 plate elements gave calculated shear and moment values that compared well with analytical values. The errors resulting from the use of fewer elements were found to be large. (2) Locations on the structure subjected to stress reversals or stress concentration are clearly indicated by the technique and show where damage due to fatique and deterioration is likely to occur. (3) Forces in cross-bracing and sway frames, which are not readily obtained in a conventional analysis, may be easily obtained. (4) Calculated deflection taking into account the three-dimensional effects of bracing and sway frames may be determined and compared with allowable values.]]></description>
      <pubDate>Fri, 29 May 1981 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/23698</guid>
    </item>
    <item>
      <title>DESIGN AND CONSTRUCTION OF AERIAL STRUCTURES OF THE WASHINGTON METROPOLITAN AREA TRANSIT SYSTEM</title>
      <link>https://trid.trb.org/View/159697</link>
      <description><![CDATA[The automated Washington, D.C. area Metro system currently under construction features precast, prestressed; cast-in-place box design; and steel with concrete deck aerial guideways.  Both single and double track structures are being constructed with various length spans.  The general features, basic and special design considerations, and rail-structure interaction of this 101-mile (163 km) system are discussed.  (Author)]]></description>
      <pubDate>Mon, 19 Jan 1981 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/159697</guid>
    </item>
    <item>
      <title>BART'S HARDWARE--FROM BOLTS TO COMPUTERS</title>
      <link>https://trid.trb.org/View/11953</link>
      <description><![CDATA[In 1965 BART began the Mt. Diablo Test Track.  Three laboratory cars were built and used to test new technology. The testing program included reduction of sound and vibration, propulsion equipment and power supply, transit vehicle trucks, automatic train operation, rails and rail support, and aerial structures, tubes, and tunnels.  Five propulsion system were tested, and dc chopper control was selected.  The Rohr built transit cars, 250 of them, feature cantilever seat construction, noise suppression, air conditioning, and glare free lighting.  The car trucks are equipped with derail detectors connected into the automatic train operation system.  On aerial structures and in tunnels, rail is fastened directly to the concrete slab or tunnel invert.  For the Berkeley Hills tunnel, which crosses the Hayward Fault, rails were mounted on timber ties to permit speedy realignment.  The Trans Bay Tube contains both horizontal and vertical curvature.  Fifty-seven prefabricated sections were floated into position, then sunk.  The Trans Bay Tube terminates in a ventilation building at each end.  Cathodic protection is used.  Welded rail was used, and the second pour technique for concrete. BART purchases power at 34.5 kvac.  This power system has seven sections.  An I section steel third rail provides strength and the top running surface for overrunning pickup shoes.  Aluminum inserts carry the current.  A J shaped cover protects against accidental contact.  Automatic train operation handles speed regulation, programmed station stops, and train door operation.  Line supervision provides best possible service schedules.  Train protection maintains the safety of the operation.]]></description>
      <pubDate>Tue, 15 Jun 1976 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/11953</guid>
    </item>
    <item>
      <title>URBAN DEVELOPMENT OF AN AERIAL GUIDEWAY PEOPLE MOVER IN THE DETROIT CBD</title>
      <link>https://trid.trb.org/View/28053</link>
      <description><![CDATA[This paper presents findings of the functional and engineering feasibility studies for an aerial guideway people mover system (PMS) within the Detroit Central Business District (CBD).  Emphasis is placed upon the process of developing alternative alignments and their evaluation.  A detailed discussion is included regarding the problems of constructing an aerial guideway within an existing urban center and how the environmental requirements are met in achieving a plan commanding broad-based community support.]]></description>
      <pubDate>Wed, 05 Nov 1975 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/28053</guid>
    </item>
    <item>
      <title>SUBSURFACE INVESTIGATION, SECTION J001, SPRINGFIELD ROUTE</title>
      <link>https://trid.trb.org/View/23943</link>
      <description><![CDATA[Results are presented of 32 borings and a number of probings made along the line of Section J001, Springfield Route, in the Valley of Cameron Run, City of Alexandria, Virginia of the Washington Metropolitan Area Metro system. The work was done for investigation of embankments and structures on the running line of METRO trackage, an aerial structure crossing over loop tracks of the Huntington-Springfield yards and certain ancillary structures.  The report contains a continuous geological section along the centerline of track through the test borings, logs of these borings, results of laboratory tests on soil samples and conclusions regarding anticipated design and construction problems.]]></description>
      <pubDate>Thu, 26 Jun 1975 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/23943</guid>
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