Denver Office of Disability Rights

Purpose

On July 26, 2001, the 10 year suspension to the provision in the Americans With Disabilities Act requiring the use of truncated domes as a detectable warning at curb ramps was lifted.  As of that date, all curb ramp construction was required to utilize truncated domes, no other alternative was acceptable.  The City and County of Denver has a curb ramp standard that does not include the use of truncated domes and has been in effect with only minor modifications since the implementation of the ADA.  This document compares and contrasts the current Denver standard with the standard required by the ADA as part of the decision making process to determine if the current standard should be maintained or if truncated domes should become a part of the City standard for curb ramp installation.

Background

The City of Denver has a long history of accessible construction predating the requirements of the Americans With Disabilities Act.  Those older ramps were not constructed using directional joint patterns or contrasting colors, but they were built to function as a means of getting mobility impaired people safely into and out of a roadway at a proper pedestrian crossing.  They closely followed the provisions of the Architectural Barriers Act of 1968.

The Americans With Disabilities Act was approved by Congress and signed into law in 1990.  Title II of the ADA, covering state and local governments, was published in the Federal Register July 26, 1991, an important date in the mandate of the use of truncated domes for detectable warning.  The provisions that apply to the installation of pedestrian curb ramps, 28 CFR §35.151(e), became effective for all roadway and sidewalk alteration or new construction on January 26, 1992.

The ADA Access Guidelines (ADAAG) contains the requirements for curb ramp construction.  ADAAG Section 4.29 requires the use of detectable warnings to provide advance warning of a potential safety hazard.  The only acceptable method of providing detectable warning, as defined by ADAAG, is by the use of truncated domes (see appendix).  The area where domes are to be placed is also to be constructed in a color that contrasts with the adjacent pedestrian path.  The use of detectable warnings is mandated for three different situations, transit platforms, hazardous sidewalk locations, and pedestrian curb ramps.  The provision for use at curb ramps was suspended by ADAAG for a period of 10 years, starting July 26, 1991, to allow for a period of study of domes in that particular usage.

Development of Denver Standard

The ADAAG guidelines were used to develop the standards adopted by Denver.  The geometric parameters, width, slope, location, etc., changed little from past documents and the Denver standard matches these.  Denver opted not to use truncated domes to meet the requirement for detectable warnings at curb ramps.

Staff for the City had concerns with the use of truncated domes for two primary reasons, removal of snow and ice during inclement weather, and potential navigation problems by people in wheel chairs traveling over the bumpy surface.  The City worked with local advocacy groups to formulate a standard that met the intent of detectable warnings but also addressed the staff concerns.

The color contrast requirement was not a difficult standard to meet.  Concrete ramps of several different colors were constructed and the contrast with adjacent sidewalk sections was measured.  Davis color #1117 (Tile Red) was chosen, it substantially met the contrast requirement, was economically feasible, and constructability was not a problem.  That color standard is in effect today.

The purpose of truncated domes is to provide a readily identifiable tactile reference for an upcoming pedestrian hazard.  The City chose to achieve this goal with the use of a defined joint pattern in the colored portion of the curb ramp.  The Denver design specifies joints at 12” intervals longitudinal and transverse with the longitudinal joints pointing in the direction of travel to reach the receiving ramp on the other side of the street.  When a single ramp is used for crossing either direction at an intersection (apex ramp), one set of joints points toward one crossing and the other points to the second crossing.  The grade change from the sidewalk to the ramp provides an additional tactile reference to the upcoming crossing.

Detectable Warning Research

Several different studies, some predating ADA, have been prepared researching the effectiveness of various forms of detectable warnings.  Some of the common threads of knowledge that came out of those studies are:

• It is essential that warnings be highly detectable.
• Consistency in detectable warnings is vital.
• Grooves, joints, patterned concrete, etc. were minimally effective.
• Vision impaired people rely on many environmental cues to provide warning of a pedestrian hazard.
• Truncated domes were the only surface that was repeatably shown to be an effective warning.
• Domes have a minimal adverse impact on people in wheel chairs.

Many different surfaces were tested for both the primary goal of providing detectable warning, and for providing a directional cue as is the standard in some foreign environs.    In Detectable Warnings: Synthesis of U.S. and International Practice, US Access Board, May 12, 2000, the following statement regarding directional surfaces is found:  “In the U.S. it is not considered necessary to provide a comprehensive tactile wayfinding system for people having visual impairments.  Blind pedestrians are instead taught to extract clues from the environment, using natural guidelines provided by such features as grasslines, fences, hedges, building lines and traffic.”  The ADAAG detectable warning standard does not provide for directional assistance at pedestrian crossings.  One study indicated that apex curb ramps had a higher incidence of unsuccessful crossings than directional ramps.

Other points of controversy were also mentioned in the Access Board document.

• “Truncated dome detectable warnings were strongly advocated by some individuals and organizations of blind travelers and the orientation and mobility profession.
• They were strongly opposed by other individuals and organizations of blind travelers and by some individuals and organizations representing people concerned with safety of persons with mobility impairments.
• Blind persons opposing detectable warnings at intersections and hazardous vehicle ways claimed that other cues were available and that detectable warnings were an unnecessary and costly feature.
• Additionally, concerns were expressed regarding the use of truncated dome detectable warnings on sloped curb-ramps and the possibility of trips and falls for sighted pedestrians, particularly women wearing high heels, as well as difficulty for wheelchair users in traversing ramps with additional “bumps”.”

Removal of snow and ice from domes was also included in the studies and none seemed to adequately address the problem.  Those groups that did not have any significant problem tended to be larger agencies or governments that had larger equipment like rotary brooms available.  A common method for snow and ice removal was through the use of chemicals, but these were not without their own set of problems, mainly with the creation of slippery surfaces with the chemicals.  Damage to the domes with plow blades was also a frequent concern.

Comparison

The following table highlights some of the more salient issues and how they are addressed by both the ADAAG and City and County of Denver specifications.  In general, the ADAAG spec focuses on the high detectability, while Denver has sought to achieve a balance to provide both a detectable approach to a pedestrian crossing, provide added benefits in directional guidance, and acknowledge the impact of ramp installations to the people responsible for maintenance and groups other than the visually impaired that utilize the ramps.

The ADAAG research noted that consistency was a vital aspect of pedestrian ramps.  There are two types of consistency, style and application.  Approximately ½ of Denver has had ramps installed.  While not all of these have directional joints or color contrast, saw cutting and surface treatment could be used on the older ramps to match the current standard.  Retrofitting all of the existing ramps with truncated domes could be done, but at a much higher cost and longer time frame.  There would be a significant length of time when more than one style of ramp would be in existence in the city, possibly leading to confusion among the public. 

Consistency in application could be an even bigger problem.  The ADA mandates the use of truncated domes for transit platforms and hazardous pedestrian areas such as linear transit stops and reflecting pools, where the goal is to warn visually impaired people that they should not proceed.  Truncated domes in curb ramps are not intended to prohibit travel, merely warn the individual they are approaching a crossing, a substantially different message and certainly adding to possible confusion at both ramps and other hazardous locations.  Detectable warnings at ramps should be different than at other locations to avoid that confusion.