Kenneth E. Lawrence

October 28, 2002

Engineered Plastics Inc
Williamsville, New York 14221

We would like to make public comment on the dome size and spacing as permitted under the new ADAAG and by the Draft Guidelines for Accessible Public Rights-of-Way.

Our research on the small diameter truncated domes, spaced farther apart, indicates that there would be a loss of slip resistance, both wet and dry, as measured by industry standard test method, ASTM C1028-89. “Determining the Static Coefficient of Friction of Ceramic Tile and Other Like Surfaces by the Horizontal Dynamometer Pull- Meter Method”. In layman’s terms, this reduced slip resistance is a result of the reduced surface area in contact with the sole of a shoe. For example, man’s shoe (size 11) is approximately 4” wide, which if placed on a center of a dome, would not extend across to reach the adjacent domes on either side, leaving the sole of the shoe to rest on only one single row of two domes, which are, in total, less than one square inch. This problem could be further compounded with a smaller shoe, and in particular a woman in high heels whose sole might be expecting to gain a sure footing on the top of a single dome.

While slip resistance can be defined and measured the issue of balance and stability is more subjective. However, with the premise of the location and size of the sole of shoes as mentioned in slip resistance, the stability for all pedestrians, and in particular the elderly or people with other disabilities may find the surface unstable, rocky and lead to losing one’s balance. Previous studies on Detectable Warning Surface design had indicated that stability was a consideration when spacing or designing the tactile surface.

In addition to the previous safety concerns that a wider spaced, small diameter dome would raise the issue of wear resistance is also a significant concern. With fewer domes, the sole of one’s shoe is impacting on fewer dome surfaces, therefore increasing the load and or friction transfer up 100 % as compared to the narrower spacing. This increased friction and load transfer will cause a much higher rate of wear, which will significantly reduce the Detectable Warning Surfaces useful life, adding significant life cycle costs and possible safety issues if the product is not replaced as it wears.
Our firms experience, in both transit and pedestrian crossing applications over the past twelve (12) years using the tighter spaced tops of domes is that, with over a million square feet of product in service, we have had no verbal or written complaints with regard to slip resistance and or stability. We question the wisdom of changing from the current standards to a new design, which does not have years of practical use in all of this country’s diverse weather conditions.

Engineered Plastic’s concerns do not stem from self-interest to maintain the status quo, as our Armor-Tile Detectable Warning Surface Tile Systems are available in the new In-Line Dome pattern, spaced 1.66” apart, which are permitted by ADAAG and by the Draft Guidelines for Accessible Rights of Way.

We trust our comments will be considered in the spirit in which they are made, to enhance the accessibility of all individuals with Disabilities without compromising the safety of all individuals.

Yours truly

Kenneth E. Lawrence
Vice-President