Detectable Warnings are used to warn someone with limited or no eyesight that they are about to enter a dangerous area such as rail tracks, a vehicular pathway or even a water feature. These warnings can literally be a life-savor for the blind.
Section 11B-705 of the California Building Code (CBC) details the specific requirements for Detectable Warnings. Some of the information included in 11B-705 includes horizontal and vertical dimensions for the required domes as well as the horizontal spacing for the domes. It also states that Detectable Warnings should be of a contrasting color and of a different texture from the surrounding surfaces. There is even a mathematical formula within the section to determine if the required visual contrast is acceptable.
In addition to requirements for size, color and texture, CBC Section 11B-705.3 states that Detectable Warnings be approved by the Division of the State Architect (DSA). This is important because several years ago, there were several products on the market that did not meet the requirements and deteriorated over time ultimately providing little or no warning to the blind.
The photograph above shows a Detectable Warning that is made out of stamped concrete. As you can see from the photograph, the domes that warn the blind that they are about to venture into traffic lanes are badly worn and now provide little if any warning for the blind. In addition, the stamped concrete provides no contrasting color to warn those with limited sight. This is one of the reasons that Detectable Warnings are to be approved by the Division of the State Architect. It’s also important to note that because the Detectable Warnings need to be of a type approved by the State Architect, they tend to be a little expensive, but are well worth the added expense as they provide a degree of safety for those individuals with limited or no vision.