Because an elevator is not a hazardous 'vehicular way.' Elevators, stairs, etc
are pedestrian features. While some warning device(s) may be recommended at
these locations, the truncated domes are specialized surface textures intended
to warn of a potential vehicular hazard and to help define the edge between the
pedestrian path and the vehicular path.

Escalators have metal plates in front covering the mechanism which provides a
sound-on-cane-contact cue. The detectable warning at a curb ramp is intended
to replace/substitute for the cue that would have been provided by the curb.
If detectable warnings proliferate, their meaning becomes diluted.

Dennis, expanding on your comments;
1. As long as the light to dark/ dark to light color contrast is maintained,
any color is ok?
2. Should TWT's be installed at the ends of access aisles that terminate at
vehicular ways?
3. What if there is a crosswalk extending from the end of an access aisle,
should a TWT be installed at the end of the aisle?
4. If your answer to "3 is yes, should there be TWT's at the otherside of the
vehicular way too?
5. Lastly, why aren't TWT's required as boundaries for crosswalks? In
particular crosswalks in parking lots that are not perpendicular to the end of
access aisles or curb ramps? How otherwise would a cane user know the limits of
the crosswalk?

light to dark/dark to light is all that is required by the ADA, Nevada uses
light green for the light contrast rather than yellow. 70% contrast is only a
suggestion based on studies conducted by Access for the Blind. Therefore any
color that meets the criteria is acceptable unless mandated by State, City,
County or Municipality.

Many private builders, cities, etc are in fact putting detectable warning at
both sides of a crosswalk or curb in parking lots where vehicular traffic goes
between two ares.

Recent FHWA research posted to our website gives additional guidance on
effective contrast. See www.access-board.gov/research/dw-fhwa/report.htm

Previous discussions about the over use of DW panels should be brought up here
again. I am seeing alot of over use in the private sector. It seems as if every
developer and/or builder is afraid to not install the DW panels at any place
where a person may enter a parking lot or building etc. Is there some way to
keep the usage for vehicular way warnings only so that the DW panels will
convey the appropriate message? With some locations it seems as if the builder
wants to do the entire walk with them. ( I saw this application while I was in
another state on vacation.) Can a statement be issued regarding this?

A4.29.2 of ADAAG as amended through September 2002 contains the requirement for
a contrast of at least 70%. Someone from the Access Board needs to comment on
whether this will be left out of the upcoming public right-of-way guidelines
and when this requirement ends.

The FHWA report Lois Thibault referred to has a very good table on page 53 as
well as color pictures of what they used for their experiments on page 11. If
you are interested in a picture of the "sidewalk" surfaces used in the
experiment, please email me individually and I will send you a file that I
received from on of the authors of the paper; I had requested this to check
what brown sidewalk actually looked like.

The contrast noted in the ADAAG Appendix was never a requirement, just advisory
information. The only DW contrast provision in draft PROWAG calls for
light-on-dark or dark-on-light contrast -- no other measure or protocol.

There has never been a requirement for any particular contrast value; the
requirement has always been light-on-dark or dark-on-light. Anything in the
Appendix (with the letter "A" in front of the number) is not mandatory. The
misunderstanding of this is the reason it is not included in the "new ADAAG" or
PROWAG. Specifying a value for contrast is meaningless without a specific test
protocol. It's one thing to measure a light reflectance value in a building
with "normal" lighting, and quite another to measure it under the variable
lighting conditions outdoors.

As far as I understand the ADAAG of contrasting colors white on dark Dark on
light or is it light next to dark and Dark next to light colors? as far I
understand it any DW placed on cement should have a border line of 4 inches all
around the DW in Black. Does anyone have any information on this?

While the ADAAG (4.29)does not specify color, it does require a light-on-dark,
dark-on-light contrast. This standard appears in the Draft PROWAG as well. The
contrast must be enough to be discernible to those with low vision (i.e., white
is not a good choice unless the surrounding ramp is considerably darker). While
many entities use the 70% contrast formula suggested in the ADAAG Appendix
(A4.29.2), as it appears to provide enough of a contrast to distinguish the
walking surface of the curb ramp from the roadway surface - it is not a
requirement (appeared more as a suggested means of measuring contrast). The
most recent Draft PROWAG does not contain the 70% contrast suggestion. Rather
than using the 70% contrast formula, I suggest consulting the study referenced
by Lois Thibault. It is a great reference guide and could be useful in making
decisions about color contrast.