March 2003

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.

Suspension of Requirements (1994 - 2001)
The Board temporarily suspended the requirements for detectable warnings in 1994 due to concerns raised about the specifications, the availability of complying products, maintenance issues such as snow and ice removal, usefulness, and safety. This suspension applied to all requirements for detectable warnings except those at boarding platforms in transit stations. The departments of Justice (DOJ) and Transportation (DOT), which maintain enforceable standards based on ADAAG, joined the Board in this action. As a result, the requirements for detectable warnings were temporarily removed from the ADA standards. The suspension expired on July 26, 2001. Consequently, the requirements for detectable warnings at curb ramps and other areas are again part of ADAAG and the enforceable standards. Questions regarding the enforceability of these requirements should be directed to DOJ or DOT.

Update of the ADA Accessibility Guidelines
During the suspension, the Board sponsored further research on detectable warnings. The Board also conducted a comprehensive review of ADAAG in an effort to update its requirements. In addition, it resumed work on developing a supplement to ADAAG specific to public rights-of-ways. Because issues concerning the use of detectable warnings are most relevant to public streets and sidewalks, the Board determined that provisions for detectable warnings on curb ramps should be addressed in rulemaking on public rights-of-ways rather than facilities on sites. As a result, the Board did not include requirements for detectable warnings at curb ramps (or hazardous vehicular areas and reflecting pools) in its proposal to update ADAAG.

Rulemaking on Public Rights-of-Ways
Currently, the Board is in the process of developing guidelines on public rights-of-ways that, once finalized, will supplement the new ADAAG. While ADAAG covers various features common to public streets and sidewalks, such as curb ramps and crosswalks, further guidance is necessary to address conditions unique to public rights-of-way. Constraints posed by space limitations at sidewalks, roadway design practices, slope, and terrain raise valid questions on how and to what extent access can be achieved. Guidance on providing access for blind pedestrians at street crossings is also considered essential.

In June 2002, the Board released guidelines on public rights-of-way in draft form and made them available for public comment. Through this release, the Board sought information and feedback, including usability and cost data, for its use in developing a proposed rule, which will provide an additional opportunity for comment in the future. The Board released a revised draft in November 2005 based on the comments received. The guidelines are based on recommendations the Board received from an advisory body it had chartered, the Public Rights-of-Way Access Advisory Committee. This committee included representation from disability organizations, public works departments, transportation and traffic engineering groups, design professionals and civil engineers, government agencies, and standards-setting bodies. The committee’s recommendations, which are contained in a report, "Building a True Community," include new specifications for detectable warnings.

The draft guidelines, consistent with the advisory committee’s recommendations, would revise the technical criteria. The revised specifications are responsive to concerns that had been raised about the impact of the truncated dome surface on wheelchair maneuvering. The Board believes that the draft revised specifications, which permit wider dome spacing, an in-line grid pattern, and smaller surface coverage at curb ramps (24 inches instead of the full ramp length, set back from the curbline) will improve usability of surfaces without affecting detectability.

Additional rulemaking steps, including another public comment period, must be completed before the Board can finalize the rights-of-way guidelines. At this time, the original detectable warning specifications in the current ADAAG remain in effect. However, ADAAG does include an “equivalent facilitation” clause (section 2.2) which permits departures from the guidelines that provide equal or greater access. The Board believes that the specifications for detectable warnings in the draft rights-of-way guidelines provide a level of access substantially equal to or greater than that currently specified by ADAAG. However, the Board does not have the statutory authority to officially make such a determination. This authority resides with the DOT and DOJ, the agencies which enforce the design requirements of the ADA. DOT, which also enforces certain ADA provisions concerning access for pedestrians, has issued guidance consistent with the Board's position.

Related Board Materials

• Suspension Notice - Extension (1998)
• ADAAG [see sections 4.1.3(15) 4.7.7, 4.29, 10.3.1(8)]
• Draft Guidelines for Public Rights-of-Ways (2005) [see sections R207 and R304]
• Advisory Committee Report: "Building a True Community" (2001)
• Status of Rulemaking on Public Rights-of-Ways
• Detectable Warnings: Synthesis of U.S. and International Practice (2000)
• List of Manufacturers
• Guidance Material on Accessible Public Rights-of-Way

Other Resources

• Department of Transportation www.fta.dot.gov (888) 446-4511 (voice/relay)
  See DOT memorandum on compliance with detectable warning requirements (May 2002)
  See DOT's ADA regulations (49 CFR Part 37.9) for determinations on equivalent facilitation
• Department of Justice www.ada.gov (800) 514-0301 (voice) (800) 514-0383 (TTY)
• Accessible Design for the Blind www.accessforblind.org (978) 838-2307