2019 California Standards for Accessible Design Guide (effective January 1, 2020 with July 1, 2021 amendments)

11B-705.1.1 General.

Detectable warnings shall consist of a surface of truncated domes and shall comply with Section 11B-705.

11B-705.1.1.1 Dome size.

Truncated domes in a detectable warning surface shall have a base diameter of 0.9 inch (22.9 mm) minimum and 0.92 inch (23.4 mm) maximum, a top diameter of 0.45 inch (11.4 mm) minimum and 0.47 inch (11.9 mm) maximum, and a height of 0.2 inch (5.1 mm).

[2010 ADA Standards] 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 inches (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).

11B-705.1.1.2 Dome spacing.

Truncated domes in a detectable warning surface shall have a center-to-center spacing of 2.3 inches (58 mm) minimum and 2.4 inches (61 mm) maximum, and a base-to-base spacing of 0.65 inch (16.5 mm) minimum, measured between the most adjacent domes on a square grid.

[2010 ADA Standards] 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 (17 mm) minimum, measured between the most adjacent domes on a square grid. 

Exception: Where installed in a radial pattern, truncated domes shall have a center-to-center spacing of 1.6 inches (41 mm) minimum to 2.4 inches (61 mm) maximum.

(a) elevation (enlarged)

(b) plan

FIGURE 11B-705.1 SIZE AND SPACING OF TRUNCATED DOMES ‡‡

11B-705.1.1.3 Color and contrast. Detectable warning surfaces shall comply with Section 11B-705.1.1.3.1. The material used to comply with this section shall be an integral part of the detectable warning surface.

Exceptions:

1. Replacement of less than 20 percent of existing detectable warnings at a single contiguous location shall be permitted to be in-kind at existing curb ramps, islands, or cut-through medians with detectable warnings in compliance with the code requirements in effect at the time of installation.

2. Existing installed detectable warnings at curb ramps, islands, or cut-through medians may comply with Section 11B-705.1.1.3.2 in lieu of Section 11B-705.1.1.3.1.

11B-705.1.1.3.1.

Detectable warning surfaces shall be yellow and approximate 33538 of SAE AMS-STD-595A.

11B-705.1.1.3.2.

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] x 100 percent where

B1 = light reflectance value (LRV) of the lighter area and

B2 = light reflectance value (LRV) of the darker area.

[2010 ADA Standards] 705.1.3 Contrast. Detectable warning surfaces shall contrast visually with adjacent walking surfaces either light-on-dark, or dark-on-light. 

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.

11B-705.1.1.4 Resiliency.

Detectable warning surfaces shall differ from adjoining surfaces in resiliency or sound-on-cane contact.

Exception: Detectable warning surfaces at curb ramps, islands or cut-through medians shall not be required to comply with Section 11B-705.1.1.4.