Knowing the law
Federal
The Americans with Disabilities Act (ADA) recognizes and protects the civil rights of people with disabilities. To ensure that buildings and facilities are accessible to and usable by people with disabilities, the ADA establishes accessibility requirements. One of those requirements is for the installation of detectable warning surfaces as indicated by the following sections of the ADA Accessibility Guidelines (ADAAG):
R304.1 General. Detectable warnings shall consist of a surface of truncated domes aligned in a square or radial grid pattern and shall comply with R304.
R304.1.1 Dome Size. Truncated domes in a detectable warning surface shall have a base diameter of 23 mm (0.9 in) minimum to 36 mm (1.4 in) maximum, a top diameter of 50 percent of the base diameter minimum to 65 percent of the base diameter maximum, and a height of 5 mm (0.2 in).
R304.1.2 Dome Spacing. Truncated domes in a detectable warning surface shall have a center-to-center spacing
of 41 mm (1.6 in) minimum and 61 mm (2.4 in) maximum, and a base-to-base spacing of 17 mm (0.65 in) minimum, measured between the most adjacent domes.
R304.1.3 Contrast. Detectable warning surfaces shall contrast visually with adjacent gutter, street or highway, or walkway surface, either light-on-dark or dark-on-light.
R304.1.4 Size. Detectable warning surfaces shall extend 610 mm (24 in) minimum in the direction of travel and the full width of the curb ramp (exclusive of flares), the landing, or the blended transition.
R304.2 Location and Alignment
- R304.2.1 Perpendicular Curb Ramps. Where both ends of the bottom grade break complying with R303.3.4 are 1.5 m (5.0 ft) or less from the back of curb, the detectable warning shall be located on the ramp surface at the bottom grade break. Where either end of the bottom grade break is more than 1.5 m (5.0 ft) from the back of curb, the detectable warning shall be located on the lower landing.
- R304.2.2 Landings and Blended Transitions. The detectable warning shall be located on the landing or blended transition at the back of curb.
- R304.2.3 Alignment. The rows of truncated domes in a detectable warning surface shall be aligned to be perpendicular or radial to the grade break between the ramp, landing, or blended transition and the street.
California (CALTRANS)
Excerpts from the 2001 California Building Code, California Code of Regulations, Title 24, Part 2, Volume 1, California Building Standards Commission
<1102A.3-C Detectable warning. Only approved DSA/AC detectable warning products and directional surfaces shall be installed as provided in the California Code of Regulations (CCR), Title 24, Part 1, Articles 2,3, and 4.
1117A.4.7 Detectable warnings. A curb ramp shall have a
detectable warning that extends the full width and depth of the curb ramp when the ramp slope is less than 1 unit vertical in 15 units horizontal (6.7% slope).
1133B.8.3 Detectable warnings at transit boarding platforms. Transit boarding platforms shall have a detectable warning texture extending the full length of the loading area.
113B.8.4 Detectable directional texture at boarding platforms. At transit boarding platforms, the pedestrian access shall be identified with a detectable directional texture.
