Detectable Warning Functionality and Compliance

Abstract

One of the most effective and commonly utilized policies to achieve barrier free access to public sidewalks, public transportation and services is the required use of Detectable Warning Panels to reliably convey distinctive tactile (feel underfoot or cane tap), auditory (sound attenuation), and visual cues (color contrast), perceptual warning cues to pedestrians - especially those that are visually-impaired or disabled - that they are transition from a safe path of travel into a potentially dangerous, life-threatening vehicular way.

The base material of Detectable Warning must be different and distinct from the surrounding walking surface in order to achieve their intended perceptual safety cues. Detectable Warning products made with Stamped Concrete, Concrete Pavers and ADA Bricks fail to provide the intended warning signals to visually-impaired pedestrians. Additionally, DWS made with Stamped Concrete, Concrete Pavers, ADA Brick and Rubber routinely fail to achieve Federal ADA specifications related to the dome geometry and height and spacing on date of installation. Certainly, within several months, depending on foot traffic, the raised truncated domes will wear poorly and become non-compliant, requiring replacement.

ADA Solutions, Inc., the leading manufacturer of Detectable Warning in North America produces the highest quality, thickest, heaviest and most UV stable detectable warning panel on the market. With over 20 years of experience and 50+ million square feet successfully installed, we remain the best option for long lasting, fully-compliant, functionally reliable DWS at very aggressive price points.

Introduction

Detectable Warning Panels are among the most effective means to enhance the safety of pedestrians, disabled persons, the visually-impaired and those individuals that text message while walking on public ways.
The purpose of this Blog post is to inform key influencers and stakeholders that detectable warning specifications are typically written by individuals that are not blind or visually-impaired. Consequently, a myriad of unsuitable materials found their way onto state, municipal and QPLs. Some of these poorly functioning materials include, but are not limited to, the following: Rubber, Concrete Pavers, ADA Bricks and Tuff-Tile (polyethylene). Products made with these materials deliver poor detectability signals, are difficult and time-consuming to install, routinely experience accelerated color fade, degradation and need for replacement. The absolute best alternative in terms of detectability, reliability, longevity and cost management is fiberglass polymer composite Detectable Warning Panels manufactured by ADA Solutions, Inc.

Background

Detectable Warning is defined as a standardized surface feature built in, or applied to, a walking surface or other elements to warn pedestrians, disabled and visually-impaired people of hazards on a walking path of travel. It is a unique and standardized feature, intended to function much like a stop sign. It alerts the visually-impaired, in addition to other pedestrians, to the presence of a hazard in the line of travel; whereupon they stop and determine the nature and extent of the hazard before proceeding further.
Detectable Warning Panels shall be installed at the bottom of curb ramps and other locations such as depressed corners, raised crosswalks and intersections, borders of medians and islands and at the edge of transit boarding platforms and where railroad tracks cross the sidewalk or any blended transition from a safe pedestrian path of travel into a potentially dangerous vehicular way. TWSI shall cover the full length of the transition and have 610mm of coverage leading into the vehicular way. The DWP should be set back 152mm – 200mm from the approach into the vehicular way. This allows wheelchair users to gain momentum while traveling over the truncated domes. It provides pedestrians, visually impaired or otherwise enough time to react to the advances TWSI warning before they reach the street or railway.
The perceptual cues associated with different sensory modalities through which detectable warning communicates information are tactile (touch), auditory (sound) and visual (sight). These three modalities work in concert to communicate information through different sensory channels. This redundant coding of information improves the chances that the traveler will detect the warning in time to respond to an impending danger. Tactile, audible and visual detection cues provide substantially higher detection rates and stopping distances in inches after detection when the detectable warning surface is a different material and texture than the surround path of travel.

Detectability Cues:

Tactile:

• Tactile cues are the most important aspect of detectable warning for many reasons. Many visually-impaired individuals do not use long canes. These people include those who are gradually losing their sight and who have not begun to use travel aids; those who have vision fluctuations and who do not always use a long cane and those who choose not to use a long cane. These people represent a larger portion of the legally-blind population than those who travel using a long cane. Therefore, having only the underfoot cue information available to enable them to locate a platform or the precise junction between curb ramp and street significantly reduces detection rates and pedestrian safety. In addition, persons who travel with guide dogs are dependent on the underfoot information regarding the changes in surface texture. Lastly, non-visually impaired persons using mobile electronic devices while traveling receive helpful tactile cues underfoot signaling them to observe their surroundings at the appropriate moment.

Visual:

• Since the primary purpose of detectable warning is to inform visually-impaired people that they are approaching a hazard, research investigating visual cues has heretofore been minimal to non-existent. However, visual cues are a tremendous value to people without visual impairments and those with low vision deficits. In particular, as an unintended consequence of mobile technology, the color contrast of detectable warning is a reliable safety cue to the multitude of pedestrians who routinely text and email while walking. This is particularly common in urban environments. 

• Fiberglass composite products provide the highest-level color contrast of all material types. Concrete Detectable Warning provides the least color contrast and slowly, over time, the panels become less effective. Since concrete and brick detectable warning is typically the same texture of the surrounding walking surface, they are difficult to detect from a distance.

Auditory:

• Auditory cues are produced by comparing the difference in sound, resulting from cane-on-surface or foot-contact-with-surface between the warning surface and the surrounding surface. 

• In one major study to systemically examine the relationship between surface detectability and texture impact noise, and rebound, found impact noise to be the single most important predictor of detectability. Audio stimuli are more difficult to detect through under-foot cues than the cane-to-surface cues. Due to the ambient noise, auditory cues can be diluted or at times masked altogether. For this reason, visually- impaired people cannot rely solely on auditory cues.

• It is important to note that there exists a strong correlation between detectable warning surfaces that omit high sound contrast with tactile vibration resulting from cane-to-surface contact. 

• The high sound contrast and tactile vibration are best facilitated as visually impaired persons approach a detectable warning surface that is of a different texture than the surrounding walking surface.

• It is very important for the detectable warning surface to be composed of an entirely different material than the entry walking surface in or around a potential hazard.

Since 1991, the implementation of Detectable Warning has been mandated in a just about all industrialized countries around the world. The overwhelming consensus derived from 50(+) years of global research and actual experience is conclusive. The effectiveness of DWS to achieve efficient and reliable long term tactile, auditory and visual warning cues is directly related to the following factors:

1. 1. Sound Attenuation
2. 2. Dome Geometry
3. 3. Dome Height
4. 4. Center-to-Center Dome Spacing 
5. 5. Color Contrast
6. 6. Long Term Durability and Performance
7. 7. TWSI shall be made of a durable material that is different from the surrounding or approach walking surface

American with Disabilities Act and TEXDOT specifications for Detectable Warning.

Tactile, audible and visual detection cues provide substantially higher detection rates and stopping distances in inches after detection when the detectable warning surface is a different material and texture than the surrounding path of travel.

The truncated domes shall have a base diameter of 23 mm (0.9 in) minimum and 36 mm (1.4 in) maximum, a top diameter of 50 percent of the base diameter minimum and 65 percent of the base diameter maximum, and a height of 5 mm (0.2 in).

The truncated domes shall have a center-to-center spacing of 41 mm (1.6 in) minimum and 61 mm (2.4 in) maximum, and a base-to-base spacing of 17 mm (0.65 in) minimum, measured between the most adjacent domes.

Problem Statement: Failure to deliver intended perceptual cues.

Detectable warning made with Concrete Stamp, Concrete Composite, ADA Brick and Rubber are functionally inadequate, frequently fail to meet Federal ADA requirements upon installation and chronically experience rapid degradation and high life cycle costs due to exceptionally high need to replace.

Concrete Pavers

Rapid color fade, dome degradation and breakage causing poor functionality and non-complaint application.

Federal Yellow Concrete Pavers

Exceptionally poor UV stability, visual cueing and is esthetically displeasing and highly prone to degradation and breakage .

Stamped Concrete

Raised truncated domes are not resilient under exposure foot traffic, shopping carts, street cleaning equipment and routine conditions – quickly rendering the installation non-compliant.

ADA Bricks

Highly susceptible to accelerated color fade and deformation of the raised truncated domes resulting in non-compliance to federal, state and municipal requirements. Labor intensive installation and repair

PROBLEM SOLUTION:

Fiberglass Polymer Composite TWSI: Distinct, Durable and Cost-Effective Solution for Municipalities, Public and Private Entities.

A durable exterior grade homogenous glass, carbon, and fiberglass reinforced composite material that’s color fast and UV stable.
Truncated domes contain fiberglass reinforcement.
A matte finish is applied on our Tactile Warning surfaces for superior slip resistance. Our colors are uniform throughout and do not rely on any type of coating to achieve UV stability.
Can be easily cut on the job site to accommodate for radius conditions, manhole covers, ballasts or other obstacles that may be present.

KEY FINDINGS:

Detectable Warning provides distinct warning signals to visually-impaired pedestrians warning them to pause as they enter into a potentially dangerous path of travel. The individual and systemic effectiveness for transmitting efficient detectability cues (touch, sound, sight) are directly correlated to the placement, strength, rigidity, UV stability of the material, color contrast, geometry, height, center-to-center spacing of the raised truncated domes, sound attenuation, vibration and long-term durability. Concrete, Brick and Rubber are substantially ineffective as TWSI and should not be permitted for use.

CONCLUSION:

• The implementation of robust DWS standards are a necessary and important step in fulfilling the state of Texas and the municipalities within DFW mission to comply with Federal ADA regulations and to continuously improve public accessibility for those among us who are confronted with visual impairment and other disabilities. 

• Since the overwhelming majority of public paths of travel are made of concrete, brick or asphalt, it is imperative to utilize DWS made of contrasting material in order to achieve optimal visual, auditory and tactile cues to assist visually-impaired persons, disabled persons, non- disabled pedestrians and those that walk on public streets or path while text messaging. 

• Hard Exterior Grade Plastic DWS provides the most reliable detection cues to visually-impaired and non-visually impaired pedestrians. 

• For the reasons detailed it is inappropriate and irresponsible install DWS made of concrete, concrete composite, brick or rubber materials into or onto walking paths that are concrete, asphalt or brick.

• Durability is critical to controlling the life cycle of fully complaint DWS. Fiberglass Polymer Composite manufactured by ADA Solutions, Inc. offers a 7-year warranty for a reason. Our products have 3 to 5 times longer functional life after installation. Thereby, saving TXDOT, municipalities and private entities substantial costs related to demolition, construction, purchase and installation of Concrete Stamp, Concrete Composite and ADA Brick that have been destroyed prematurely or have been rendered non-compliant shortly after installation.

ABOUT ARCO

For over ten years Arco Contractor Supply has delivered top quality construction products, materials and services to the Dallas - Fort Worth Market. At Arco we are fully committed to exceeding the expectations and demands of our customers. We strive to provide aggressive pricing, unparalleled customer service and technical counsel.

Blog Post Written By Brad D'Andrea at ADA Solutions