Guidelines for Nighttime Visibility of Overhead Signs (2016) / Chapter Skim
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62 Guidelines for Nighttime Overhead Sign Visibility A P P E N D I X D This appendix contains recommendations for revised material specifically for the AASHTO Roadway Lighting Design Guide. The latest edition (2005)
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63 Signs in areas where atmospheric conditions create condensation or frost on the sign face and reduce the effectiveness of the retroreflective sheeting. Key Visibility Considerations for Overhead Sign Lighting The following considerations should be addressed to assess nighttime sign visibility.
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64 Table D-1. Luminance Levels for Overhead Signs.
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65 Level 1 Visual Complexity: Minimal objects and light sources. Low traffic.
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66 Level 1 Visual Complexity: Minimal objects and light sources. Low traffic.
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67 Visual Complexity Levels for Overhead Street Name Signs The images in Figures D-3 and D-4 were developed and tested to show five levels of visual complexity for overhead street name signs (at signalized intersections)
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68 Level 1 Visual Complexity: Minimal light sources, signs, and objects. Low traffic.
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69 Level 1 Visual Complexity: Minimal light sources, signs, and objects. Low traffic.
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70 10.3 ILLUMINATED SIGN TYPES Signs can be illuminated in a variety of different ways in order to make the sign message visible and legible to the passing motorist during the hours of darkness. The two main ways of providing illumination to a static sign are as follows: Externally Illuminated -- Externally illuminated signs are static traffic signs that are uniformly illuminated by a source of light that is mounted external to the sign.
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71 together will provide poor contrast between the letters that make up the legend and the background of the sign, making it more difficult to read. A maximum-to-minimum uniformity ratio of 6 to 1 is recommended as an acceptable ratio of lighting levels on the face of the sign.
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72 the bottom of the sign, or an adjacent support. The lighting engineer should evaluate the following considerations before selecting the mounting arrangement that is to be utilized.
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Abbreviations and acronyms used without definitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACI–NA Airports Council International–North America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FAST Fixing America's Surface Transportation Act (2015) FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012)
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TRA N SPO RTATIO N RESEA RCH BO A RD 500 Fifth Street, N W W ashington, D C 20001 A D D RESS SERV ICE REQ U ESTED N O N -PR O FIT O R G .
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