NEWS

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.

Truncated domes are a unique design and have proven to be the most detectable surface.

Detectable Warning Products: Final Rule

After 10 years of research on detectable warning products, the Americans with Disabilities Act Accessibility Guidelines (ADAAG) have concluded that only one product on the market has made the cut.  There were several options available before a suspension was placed on the requirement for detectable warning products on hazardous vehicular ways in 1991, such as grooves or exposed aggregate.  The suspension was applied to determine the actual effectiveness of these systems, and whether or not they actually help the visually impaired detect boundary changes in the street.  Now the suspension has been lifted and the results are in:  most detectable warning products are indistinguishable between pavement texture, or cracks and joints in the road – but not all. 

Truncated domes, a unique design consisting of domes, approx. 5mm high, flattened on the top and arranged in a square pattern.  The design was developed by the Japanese who were attempting to make up for the lost information due to the removal of curbs.  (Curbs were non-visual cues of an intersection; however, accessibility laws have eliminated many curbs from street design for the mobility-impaired.) 

Since then, and more importantly since the ADAAG regulation was passed, numerous manufacturers entered the market. The detectable warning products differed slightly in execution of the truncated dome dimensions and spacing as well as materials. Truncated dome products soon included resilient sheet material, dimensional pavers, tiles, polymer composites, bricks, pre-cast concrete, stamped concrete and applied surfaces. 

There is no question that the visually impaired society faces large challenges, and deserves our commitment to a safe community.  And as far as detectable warning products go, truncated domes are the best – and the only – option.

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