18.6 Conspicuity of Diamond Warning Signs Under Nighttime Conditions

  • Visual conspicuity refers to how easily road users can locate a visual target. When motorists can identify signs easily, they have more time to process information found on the signs and react accordingly. As the conspicuity of a sign increases, the likelihood of motorist missing or being unable to read the sign decreases.
  • Sign characteristics and/or the surrounding environment can be modified to improve sign conspicuity (Table 18.3).
Table 18.3 Guidance for Improving Sign Conspicuity
Sign Characteristics Environment Characteristics
  • Increase sign brightness relevant to the ambient environment
  • Increase brightness contrast between different part or elements of the sign
  • Increase the sign’s size so it stands out relative to other objects in the motorist’s visual field
  • Select a sign hue that contrasts with other noise/background items
  • Reduce the number and density of background noise items. Focus particularly on items near the sign
  • Increase the distance between the sign and noise items.
  • The visual complexity of the environment in which a sign is embedded strongly influences its visibility and luminance requirement. Because older motorists have more difficulty detecting and recalling information from signs and are more slow to respond than younger motorists, their needs should be a foremost concern and guide decisions about sign placement and sizing.

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Chris VanDyke

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chrisvandyke@uky.edu