Detectible Warning Depth

Question:  What is the depth requirement for detectable warnings at curb ramps?

The Americans with Disabilities Act Accessibility Guidelines (ADAAG) written by the U.S. Architectural and Transportation Barriers Compliance Board (Access Board) and published July 26, 1991, includes the following section:

4.29 Detectable Warnings.

4.29.5 Detectable Warnings at Hazardous Vehicular Areas.

“If a walk crosses or adjoins a vehicular way, and the walking surfaces are not separated by curbs, railings, or other elements between the pedestrian areas and vehicular areas, the boundary between the areas shall be defined by a continuous detectable warning which is 36 inches wide, complying with 4.29.2.”

The Americans with Disabilities Act (ADA) recognizes and protects the civil rights of people with disabilities and is modeled after earlier landmark laws prohibiting discrimination on the basis of race and gender.  To ensure that buildings and facilities are accessible to and usable by people with disabilities, the ADA establishes accessibility requirements for sate and local government facilities, places of public accommodation, and commercial facilities.  Under the ADA, the Access Board has developed and continues to maintain design guidelines for accessible buildings and facilities; these guidelines are known as the ADAAG.  ADAAG covers a wide variety of facilities and establishes minimum requirements for new construction and alterations.

The Revised Draft Guidelines for Accessible Public Rights-of-Way, written by the Access Board and published November 23, 2005, includes:

Chapter R3 Technical Provisions.

R304 Detectable Warning Surface.

R304.1.4 Size.

“Detectable warning surfaces shall extend 24 inches minimum in the direction of travel and the full width of the curb ramp (exclusive of flares), the landing, or the blended transition.”

Now we have a 36 inch requirement in a 1991 Access Board guideline and a 24 inch requirement in an 2005 Access Board guideline.  The Access Board is the U.S. Government agency responsible for writing the design guidelines for buildings and facilities to be in compliance with the ADA.  

In the opinion of ACCESS, the 24 inch detectable warning depth is in compliance with the ADA Compliance.

The above are opinions of Hank Falstad, AIA, Managing Senior Associate of Access Technologies Services, Inc. (ACCESS).  See our web site for additional information:  http://www.accessts.net/.