Detectable Warnings (aka Truncated Domes)

vocabularyOften jargon can become a barrier in communication.  We’d like to devote some real estate at this blog to not only define but shed light on industry terms as well as news and project profiles.

In October 2009, I took a photo of yellow tiles separating the platform from the rails at the Santa Ana Train Depot and sent it to twitter with the question, “The yellow bumpy things are called…”  The answer is: truncated domes.

Detectable warnings are required when constructing and altering curb ramps. According to Detectile, truncated domes are the only tactile warnings allowed by ADAAG. Below you will find two quotes from



In the absence of a definitive cue—the curbed sidewalk—at the sidewalk/street boundary, it has become much more difficult for pedestrians who are blind to detect streets. When blind pedestrians do not detect a curb at the end of a block, they must rely on multiple clues which, taken together, indicate the high probability that they have come to a street. They may detect a change in slope, which could be a curb ramp, a change in terrain, or a broken sidewalk.

Detectable Warning Synthesis

Detectable warnings, a distinctive surface pattern of domes detectable by cane or underfoot, are used to alert people with vision impairments of their approach to streets and hazardous drop-offs. 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.

ADAAG Requirements for Detectable Warnings

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