I'm not aware of any federal standards with respect to degradation limits, but
California passed an Assembly Bill (AB685) in 1999, which requires "...that the
[truncated domes] product maintains at least 90 percent of its approved design
characteristics. ..."
See
info.sen.ca.gov/pub/99-00/bill/asm/ab_0651-0700/ab_685_bill_19990830_enrolled.ht
ml.

Jurgen

Florida DOT has established some "acceptance criteria" for detectable warnings
- especially the formed-in-place types. The criteria are: 1) 90% of the
individual truncated domes must comply with the design criteria, 2) There may
be no more than 4 non-complying domes in any one square foot of surface 3) No
two adjacent domes may be non-compliant. In this case 'non-compliant' includes
any poorly formed domes, not just missing one.

Tile Tech Pavers is the leading manufacturer in precast Detectable Warning
Pavers & ADA Truncated Dome Pavers & Tiles meeting all ADAAG (4.29)
requirements. Our pavers are available nationally and are manufactured in a 700
ton hydraulic press resulting in a product that is 8,000 to 10,000 psi, (55
Mpa.) & less than 1% loss of weigh in Freeze Thaw conditions. These precast
Detectable Warning Pavers & ADA Truncated Dome Pavers come in 12"x 12" x 2" &
12"x 12" x 1" with a dome base diameter of 0.90" & a dome top diameter of 0.45"
with dome spacing form center to center at 2.35". They also come in in-line
formation for easy wheelchair access & in staggered formation to meet all DOT
requirements

They available in four standard colors, Charcoal, Yellow, Natural & Red, custom
colors are also available. Our standard colors provide the flexibility of
having a 70% contrast to the adjacent area as suggested in the ADAAG (A4.29.2).
This general formula appears to provide enough of a contrast to distinguish the
walking surface of the curb ramp from the roadway surface. Our pavers are
available nationally & are very economical especially for cities & government
projects. Pricing for our Detectable Warning Pavers & ADA Truncated Dome Tiles
varies between $5.00 – $7.00 per sqft. We are also approved by many states DOT
& are on their list of Approved Manufacturer/Products.

You can also see our product @ www.tiletechpavers.com/DetectablePavers.html

You can visit our site for PDF file of the full ADA Accessibility Guidelines @
www.tiletechpavers.com/DetectablePavers.html

Can the Administrator please re-visit the issue of using this website as a
forum for selling products? This website is so very useful concerning a
variety of topics, and I do not care to read advertisements. I would
appreciate thoughts of other users who concur.