Visibility Performance Requirements and Testing Procedures for Pedestrian Signal Heads

Details

• Creators:
  Finley, Melisa D. ; Holick, Andrew J.
• Corporate Creators:
  Texas A&M University System. Texas Transportation Institute
• Corporate Contributors:
  Texas Department of Transportation. Research and Technology Implementation Office ; United States. Department of Transportation. Federal Highway Administration
• Subject/TRT Terms:
  Compliance Daylight Glare Light Emitting Diodes Luminance Night Specifications Test Procedures Visibility
• Publication/ Report Number:
  FHWA/TX-04/0-4447-1
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States
• Edition:
  September 2002-August 2003
• Corporate Publisher:
  Texas. Department of Transportation
• Abstract:
  Historically, pedestrian signal heads have been internally illuminated using incandescent lamps. However, with the current widespread use of light emitting diodes (LEDs) in pedestrian signal heads, concerns regarding the visibility of LED devices have emerged. Research was needed to develop measurable visibility performance requirements for pedestrian signal heads, as well as test methods to verify compliance with these requirements. Researchers solicited expert opinions concerning the minimum luminance necessary for the daytime recognition of the walking person and upraised hand indications. The findings indicated that the minimum luminance values proposed by the Institute of Transportation Engineers (ITE) (5300 cd/sq m and 3750 cd/sq m) should provide an adequate level of brightness for daytime recognition of the walking person and upraised hand indications, respectively. Through a nighttime discomfort glare study, researchers determined the median glare threshold for the walking person and upraised hand indications to be approximately 3100 cd/sq m and 2600 cd/sq m, respectively. Since these values are less than the minimum luminance levels proposed by ITE, researchers recommended that pedestrian signals be dimmed at night. In addition, the discomfort glare study findings indicated that the ITE minimum dimmed luminance requirement (i.e., 30% of the minimum luminance values) will provide an adequate level of brightness for nighttime recognition of the walking person and upraised hand indications. Researchers also evaluated two test methods by which to measure the luminance of pedestrian signal indications. The ITE proposed test method measures the luminance of a pedestrian signal indication at nine separate points on the indication's surface, while the full indication method measures the luminance of an entire indication in one measurement. Researchers recommended the use of the full indication test method to verify compliance with the recommended visibility performance requirements.
• Format:
  PDF
• Funding:
  0-4447
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:ea29b7df93c81a220dd7bd1654090bd428e25c28e75394c767a5a1414adec593fca8ced53d573167584314e38af269f4556ff957b922179536bd6e9306c02979
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/87796/dot_87796_DS1.pdf
• File Type:
  [PDF - 716.29 KB ]