ADA/ABA Guidelines - Detectable Warnings

705.1 General. Detectable warnings shall consist of a surface of truncated domes and shall comply with 705.

705.1.1 Dome Size. Truncated domes in a detectable warning surface shall have a base diameter of 0.9 inch (23mm) minimum and 1.4 inches (36mm) maximum, a top diameter of 50 percent of the base diameter to 65 percent of the base diameter maximum, and a height of 0.2 inch (5.1mm).
705.1.2 Dome Spacing. Truncated domes in a detectable warning surface shall have a center-to-center spacing of 1.6 inches (41mm) minimum and 2.4 inches (61 mm) maximum, and a base-to-base spacing of 0.65 inch (17mm) minimum, measured between the most adjacent domes on a square grid.
705.1.3 Contrast. Detectable warning surfaces shall contrast visually with adjacent walking surfaces: either light-on-dark, or dark-on-light.
705.2 Platform Edges. Detectable warning surfaces at platform boarding edges shall be 24 inches (610mm) wide and shall extend the full length of the public use areas of the platform.

Walking Surfaces
4.29.2* Detectable Warnings on Walking Surfaces. Detectable warnings shall consist of raised truncated domes with a diameter of nominal 0.9 in (23 mm), a height of nominal 0.2 in (5 mm) and a center-to-center spacing of nominal 2.35 in (60 mm) and shall contrast visually with adjoining surfaces, either light-on-dark, or dark-on-light. 
*Appendix Note: The material used to provide contrast shall be an integral part of the walking surface. Detectable warnings used on interior surfaces shall differ from adjoining walking surfaces in resiliency or sound-on-cane contact.
4.29.3 Detectable Warnings on Doors To Hazardous Areas. (Reserved).
4.29.4 Detectable Warnings at Stairs. (Reserved).
4.29.5 Detectable Warnings at Hazardous Vehicular Areas. If a walk crosses or adjoins a vehicular way, and the walking surfaces are not separated by curbs, railings, or other elements between the pedestrian areas and vehicular areas, the boundary between the areas shall be defined by a continuous detectable warning which is 36 in (915 mm) wide, complying with 4.29.2.
4.29.6 Detectable Warnings at Reflecting Pools. The edges of reflecting pools shall be protected by railings, walls, curbs or detectable warnings complying with 4.29.2.

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