Truncated Domes Regulations

In the U.S. tactile warnings systems are required by the ADA. The federal government, through studies and guidance provided by advocates and the Access Board^[2] now mandates detectable warnings in prescribed locations, such as on the surface of pedestrian curb cuts and at the edge of rail platforms. Detectable warnings have been required for the edge of rail platforms in the United States since 1991. Detectable warnings for pedestrian curb cuts were suspended for study in 1994, and became officially required in 2001.

The ADA Accessibility Guidelines (ADAAG) require these warnings on the surface of curb ramps, which remove a tactile cue otherwise provided by curb faces, and at other areas where pedestrian ways blend with vehicular ways. They are also required along the edges of boarding platforms in transit facilities and the perimeter of reflecting pools. The raised pattern of domes also known as truncated domes are the preferred design for detectable warning tiles and pavers.
The usage of tactile paving in many circumstances will be required in the United States as part of the Americans with Disabilities Act.^[3] Adoption of truncated dome-mats has been controversial in some areas including Sacramento, CA.^[4]
Specifications for current enforceable ADA detectable warnings truncated domes regulation for the general public, is the United States Department of Justice 28 CFR part 36 Revised as of July 1, 1994.
Excerpt from ADA 4.3 Accessible Routes, 4.3.6 Surface Textures, 4.5 Ground Floor Surfaces, 4.5.3 - Carpet, 4.5.4 - Gratings - Textures. To date it appears none-of the detectable warnings manufactured, comply with 4.3.6 of the ADAAG. In addition, testing for being a non-hazardous surface placed in public walkways has not been conducted. In the appendix - some common sense reasons are illustrated about textures and their effects on the mobility impaired - A.4.5 Ground and Floor Surfaces. A4.5.1 General. People who have difficulty walking or maintaining balance or who use crutches, canes, or walkers, and those with restricted gaits are particularly sensitive to slipping and tripping hazards. For such people, a stable and regular surface is necessary for safe walking, particularly on stairs. Wheelchairs can be propelled most easily on surfaces that are hard, stable, and regular. Soft loose sand or gravel, wet clay, and irregular surfaces such as cobblestones can significantly impede wheelchair movement. 705 below has not been adopted by the DOJ for the general public and is therefore not enforced by the DOJ.
Specifications for ADA Detectable Warning Truncated Domes United States Access Board – ADAAG Specifies:
705 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 (23 mm) minimum and 1.4 inch (36 mm) maximum, a top diameter of 50 percent of the base diameter minimum to 65 percent of the base diameter maximum, and a height of 0.2 inch (5.1 mm).
705.1.2 Dome Spacing. Truncated domes in a detectable warning surface shall have a center-to-center spacing of 1.6 inches (41 mm) 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.