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.

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.

http://www.access-board.gov/Adaag/dws/update.htm