Evaluation of
Detectable Warning Surfaces
FINAL REPORT
Prepared for the
Sacramento Regional Transit District
March 1997
Crain & Associates, Inc.
120 Santa Margarita Ave.
Menlo Park, CA 94025
(415) 323 - 3444
Accessible Design
for the Blind
Mobility and Wayfinding
Consultants
RECOMMENDATION
RT should use a specification based on Armor Tile as the preferred product for use in retrofitting all existing stations and installation in planned future stations.
The evaluation has identified only three products which, based on the tests conducted and reported experience, are known to be in full compliance with the requirements of ADA and Title 24 of the California building code. They are Armor Tile, manufactured by Engineered Plastics, Inc., Pathfinder, manufactured by Carsonite International, and Detectable Warning Mat, manufactured by Detectable Warning Systems. Carsonite International declined to participate in field tests, saying its product was not appropriate for outdoor use; therefor it was eliminated from further consideration. Since then, Carsonite has withdrawn its product from manufacturing. Armor Tile and Detectable Warning Systems product were both determined to have good performance with respect to detectability by blind travelers and visibility to travelers with limited vision. However, Armor Tile is preferred for reasons on safety, durability of installation, long-term cost, and aesthetics.
CONCLUSIONS
The evaluation shows that Armor Tile is clearly the preferred product for use at RT based on the available information and the field tests. Armor Tile's good ratings and compliance with Title 24 depend crucially on the sound difference between it and the adjoining platform. This sound difference appears to depend primarily on the way the product is installed, rather than the material of which it is made. High Quality also showed some sound difference, also apparently as a result of its installation. However, this difference was inconsistent and not sufficiently reliable to be used for purposes of detection.
Table C.4
Surfaces which were judged easiest to detect.
|
Surface
|
Number
|
Reasons
|
| Armor Tile |
15*
|
could hear the difference in all kinds of weather; pitch difference; easy to detect under foot; loudest; could hear even if distracted; sound different from the others; echo-y; hollow sound; best for cane. |
| High Quality |
1
|
louder; bumpier; distinct sound |
| Interlock |
0
|
|
| Detectable Warning Systems |
6*
|
more certain under foot; I'm sure I'd hear it; sound difference; best under foot; feels different- grabs cane |
| No choice |
1
|
* Three participants identified both Armor Tile and Detectable Warning System as being easiest to detect.
Participants were also asked to identify, by number, the surface they found most difficult to detect. Table C.5 shows the number of participants who identified each surface as most difficult to detect. and the reasons given for the difficult detectablility of that surface.
Table
C.5
Surfaces which were judged most difficult to detect.
|
Surface
|
Number
|
Reasons
|
| Armor Tile |
0
|
|
| High Quality |
2
|
less pronounced; feels more like platform; feels like bumps are lower |
| Interlock |
10
|
flat bumps are hard to detect under foot; most similar to platform; feels like concrete; no sound difference; not secure-feels rocky; feels like other rough surfaces; same sound as platform |
| Detectable Warning Systems |
4
|
not detectable under foot; In noisy conditions I'd miss it; would walk past it if I didn't hear it; doesn't have great sound; worried about it expanding and contracting |
| No choice |
3
|
* Three participants did not identify any surface as being hardest to detect.