11B-705.1.1.3 Color and Contrast
Detectable warning surfaces at transit boarding platform edges, bus stops, hazardous vehicular areas, reflecting pools, and track crossings shall comply with Section 11B-705.1.1.3.1. Detectable warnings at other locations shall comply with either Section 11B-705.1.1.3.1 or Section 11B-705.1.1.3.2. The material used to provide visual contrast shall be an integral part of the surface.
Detectable warning surfaces shall be yellow and approximate FS 33538 of Federal Standard 595C.
Detectable warning surfaces shall provide a 70 percent minimum visual contrast with adjacent walking surfaces. Contrast in percent shall be determined by:
Contrast percent = [(B1-B2)/B1] × 100 where
B1 = light reflectance value (LRV) of the lighter area and
B2 = light reflectance value (LRV) of the darker area.
Exception: Where the detectable warning surface does not provide a 70 percent minimum contrast with adjacent walking surfaces, a 1-inch (25 mm) wide minimum visually contrasting surface shall separate the detectable warning from adjacent walking surfaces. The visually contrasting surface shall contrast with both the detectable warning and adjacent walking surfaces either light-on-dark, or dark-on-light.