FHWA endorses the 24" deep strip of DWs because we have determined, under the
"equivalent facilitation" standard in ADAAG (2.2), where it states "Departures
from particular technical and scoping requirements
of this guideline by the use of other designs and technologies are permitted
where the alternative designs and technologies used will provide substantially
equivalent or greater access to and usability of the facility." We have
determine this to be the case with the 24" strip. However, the US Department
of Justice, in Chapter 6 of its ADA Tool Kit (curb ramps), illustrates the use
of both the ADAAG standard in 4.7.7 (full depth and width) and the FHWA
standard (see pages 10 and 11). You can obtain Chapter 6 of the USDOJ Tool Kit
at www.ada.gov/pcatoolkit/ch6_toolkit.pdf

With respect to the issue of private developments, you need to confirm whether
at completion, the development will stay private (gated community) or it will
be turned over or "dedicated" to the local government. Since sidewalks in
residential areas are "facilities" within the meaning of Title II ADA (State
and Local Government Programs), residential sidewalks that are constructed with
the expectation that they will be turned over to the local government are
required to be accessible to people with disabilities. A local government can
impose this requirement via ordinance, as a condition of plan or permit
approval, withholding the release of bond/escrow to the developer or other
methods to accomplish this. If, however, the sidewalks were constructed by a
private developer as part of a purely private residential development, such as
a gated community, the ADA would not apply at all. Nevertheless, be sure to
check any State and local accessibility guidelines, statutes, ordinances,
permits or development plan approvals, as they could require that accessible
features be installed on sidewalks in a private community.

Bob, I'd like to ask what criteria the FHWA used to determine that the 24" DW
strip provided equivalent facilitation.

We're trying to understand how organizations like yours and others apply the
concept.

Many studies over the years have shown that a 2-foot strip of DW is effective
for alerting blind persons. These studies are the basis for the requirement at
transit platforms, arguably a more serious condition than most streets. The
original curb ramp requirement stems from a debate over where the DW should be
placed. Some people thought it should be at the bottom of the ramp, some
thought it should be at the top, and some suggested it should surround the
entire ramp, including the flares (this is the placement of the grooves
California has required for years). The "full width and depth" was really a
compromise. Over the years, it has become apparent that this is over kill.

If the development is say an industrial or commercial development with public
access, then ADA would have to apply. It is in these types of circumstances
that the type of DW device comes into question.