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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>SERVICE LIFE OF BUTTON SIGN COPY</title>
      <link>https://trid.trb.org/View/50559</link>
      <description><![CDATA[Both prismatic-button and reflective-sheeting legend materials are used for copy on New York's signs. Enclused-lens sheeting ("engineer" grade), used in the past, is shorter-lived and less bright than buttons; recently introduced encapsulated-lens sheeting ("high-intensity" grade) is a serious contender to buttons in this application.  This study was undertaken to determine button copy service life on New York's highways.  The findings showed 1) that button copy provides acceptable brightness for about 12 years, 2) by 12 years nearly all buttons have cracked to some degree, resulting in reduced brightness, 3) clearcoating, found on 10 percent of the buttons, causes an unacceptable loss of brightness, 4) deterioration of copy frames was usually slight and did not impair daytime legibility (those damaged to the extent that buttons were lost did lose nighttime legibility), 5) sign directional orientation did not appear to affect service life, 6) dirt accumulation and its effects on brightness were negligibile, and 7) at high angularity )large divergence and incidence angles) button reflectivity was less sensitive to age.]]></description>
      <pubDate>Mon, 13 Oct 2003 00:00:00 GMT</pubDate>
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      <title>OPTIMIZATION OF POST DELINEATOR HEIGHT AND SPACING. FINAL REPORT</title>
      <link>https://trid.trb.org/View/274532</link>
      <description><![CDATA[This project involved an analytical optimization of the height, spacing and lateral offset of flexible post delineators for tangent sections and horizontal curves.  It also involved a small scale field demonstration and evaluation by ODOT and FHWA personnel.  The analytical optimization was conducted on a microcomputer and was based solely upon visibility considerations.  For tangent sections an optimal spacing of 275 feet is recommended for encapsulated sheeting materials, while a spacing of 350 to 400 feet is recommended for prismatic sheeting materials. For curved sections of four-lane divided highways flexible post delineators should be spaced according to 9.8 times the cubic root of (R-40) for encapsulated lens sheeting materials (specific intensity 309 cd/fc/sqft), 11.5 times the cubic root of (R-45) for prismatic sheeting (specific intensity 825 cd/fc/sqft), and 13.5 times the cubic root of (R-47) for prismatic sheeting (specific intensity 1485 cd/fc/sqft) where R is the curve radius in feet.  For curved sections of two-lane highways, bidirectional delineators should be spaced according to 10 times the cubic root of (R-43) for encapsulated lens sheeting material (specific intensity 309 cd/fc/sqft), 11.5 times the cubic root of (R-44) for prismatic sheeting material (specific intensity 825 cd/fc/sqft) and 13 times the cubic root of (R-46) for prismatic sheeting materials (specific intensity 1485 cd/fc/sqft).  The effects of height and lateral offset upon visual detection are minimal and negligible.  The field evaluation indicated that the spacings for the prismatic sheeting material provided the best delineation performance and that a vertical prismatic reflector strip of 18 x 1 inches provided the best reflective and delineation performance.  Further, a red 18 x 1 inch prismatic sheeting strip on the backside of flexible post delineators on four-lane divided highways near intersections would help a lot to indicate wrong lane and wrong direction.  Two black 30 degree slanted 6 inch strips in the top section of the flexible post delineator would help during the daytime in snow.]]></description>
      <pubDate>Tue, 31 Mar 1987 00:00:00 GMT</pubDate>
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      <title>LIMIT DESIGN OF PRESTRESSED CONCRETE BRIDGES</title>
      <link>https://trid.trb.org/View/99776</link>
      <description><![CDATA[THIS ARTICLE PRESENTS A LIMIT DESIGN THEORY FOR THE DESIGN OF PRISMATIC AND NONPRISMATIC CONTINUOUS PRESTRESSED CONCRETE GIRDER BRIDGES SUBJECTED TO MOVING LOADS. AN EXAMPLE HAS BEEN WORKED OUT TO ILLUSTRATE THE APPLICATIONS OF THE THEORY. IN COMPARISON WITH OTHER METHODS THE PROPOSED SYSTEM REALIZES CONSIDERABLE SAVINGS. THE DESIGN ENGINEER COULD CARRY OUT THE LIMIT ANALYSIS SO THAT IT GIVES A MORE ACCURATE REFLECTION OF ACTUAL CONDITIONS IN THE STRUCTURE AND, THEREFORE, A REALISTIC FACTOR OF SAFETY. WHILE NOT FULLY ADOPTED, THE CONCEPT OF LIMIT DESIGN FOR REINFORCED CONCRETE HAS ALREADY BEEN INCORPORATED IN VARIOUS FORMS IN THE ACI BUILDING CODE AND IN THE CODES OF PRACTICE OF THE U.K., U.S.S.R., DENMARK, AND NORWAY. /DOT/]]></description>
      <pubDate>Wed, 13 Dec 1972 00:00:00 GMT</pubDate>
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