Detectable Warnings:

Synthesis of U.S. and

International Practice

Work performed under contract by:

Billie Louise Bentzen, Ph.D.

Janet M. Barlow, COMS

Lee S. Tabor, architect

Accessible Design for the Blind

P.O. Box 1212

Berlin, Massachusetts 01503 USA

978-838-2307 voice / fax

bbentzen@ma.ultranet.com

12 May 2000

U.S. Access Board • 1331 F Street, NW • Suite 1000 • Washington, DC 20004-1111

(800) 872-2253 (Voice) • (800) 993-2822 (TTY) • (202) 272-5447 (Fax)

info@access-board.gov (E-mail) • http://www.access-board.gov (Website)
2 U.S. Access Board  Detectable Warnings: Synthesis

Acknowledgements

The authors wish to express their appreciation to all who generously contributed their

time and efforts in providing information, specifications, and photographs, to those who

participated in interviews, and to those who gave permission for us to list their names in

this publication as contacts for more information.

The authors are thankful to Lois Thibault of the U.S. Access Board for the provision

of difficult to obtain resources, and for her careful editing and suggestions on content

organization.

We also wish to acknowledge the dedicated research assistance of Abigail Tabor and

Rebekah Barlow.

Illustration Credits

All drawings by Lee Tabor except as noted.

All photos by the authors except as noted.

Photos by Martin Miller: cover, 8-15 through 8-30.

Photos by Lois Thibault: 1-3, 1-4, 2-5, 3-7, 4-4, 4-13, 5-1, 5-2, 5-3, 5-5, 5-11.

Photos by Murray Mountain: 3-5, 4-6, 4-13, 4-14.

Photos by Douglas Barlow: 2-4, 3-6, 5-8.

Photos by Lukas Franck: 5-6, 5-14.

Photos by Ken Zimmerman: 5-7, 6-2.

Photo by Barry Eager: 3-1.

Photo by Robert Laurie: 5-4.

Photos courtesy of Beneficial Designs: 4-5, 4-7.

Photo courtesy of Rick McCarter: 5-10.

Photo courtesy of Maryvonne Dejeammes: 4-10

Photos reproduced, with permission, from König, 1996: unnumbered, p. 64, 4-11, 4-12.

Photo reprinted from Ketola & Chia, 1994: 3-3

Drawing by Joanne Bergen reproduced from Bentzen et al., 1994: 2-6.

Drawing reproduced, with permission, from Guidance on the use of tactile paving surfaces,

1998: 3-4.

Drawings reproduced, with permission, from ÖNORM V 2102: 4-1, 4-2.

Drawing reproduced, with modification, by permission, from Sawai et al., 1998: 4-3.

Photos and drawings from manufacturer’s brochures: Engineered Plastics, 1-7; Disability

Devices: 1-8; Architectural Tile & Granite: unnumbered, p. 26; Summitville, 5-12;

Carsonite; 5-15; Strongwall Industries: 7-8, 7-9; Increte: 7-10; Cote-L: 7-11, 7-13, 7-14;

Vanguard ADA Products: 7-12.
U.S. Access Board  Detectable Warnings: Synthesis 3

Contents  Detectable Warnings:

Synthesis of US and International Practice

Introduction Content of synthesis / 11

Purpose of synthesis / 11

Sources of information / 11

Chapter 1. Background

How people who are

blind detect streets

Curbs are a definitive cue / 14

How curbs are detected / 14

Elimination of curbs / 15

The need to rely on multiple clues / 15

The difficulty of finding and using multiple clues / 15

Detecting transit

platform edges

Techniques for detecting transit platform edges having a drop-off / 16

Blind people at risk at transit platform edges / 16

Early solutions Japan / 17

United Kingdom / 17

U.S. research to

identify detectable

warning surfaces

Extensive research program on detectability / 18

Importance of under foot detectability / 18

Early projects / 19

Surfaces for transit platforms / 19

Surfaces with low detectability / 20

History of

U.S. standards

ANSI A117.1-1980Tactile warnings / 21

Specification of texture / 21

ANSI A117.1-1986Detectable warnings / 21

Implementation of ANSI A117.1-1980 & 1986 / 22

ADAAG (1991)Truncated dome detectable warnings / 23

Controversy in the U.S. / 23

ANSI A117.1-1992Deleted detectable warning specifications / 23

Some ADAAG requirements for detectable warnings suspended / 24

Research on detectable warnings recommended / 24

Rights-of-way guidelines / 24

Local and state guidelines / 25

Variety of recommendations / 25

ICC/ANSI A117.1-1998Equivalent detectability / 25
4 U.S. Access Board  Detectable Warnings: Synthesis

Contents  Detectable Warnings: Synthesis, continued

Other textured

walking surfaces

Other surfaces / 26

Raised design flooring / 26

Directional tactile paving / 26

Truncated dome

detectable warnings

Focus on truncated dome detectable warnings / 27

ADAAG-compliant detectable warning at curb-ramps / 27

Chapter 2. Detectable Warnings in ADAAG

Definition &

specification

Definition of detectable warnings / 30

Specification for detectable warnings / 30

Visual contrast / 30

Geometry of

detectable warnings

Dome alignment & pattern / 31

Dome profile / 31

Detectable

warnings at transit

platform edges

Requirement for transit platform edges (ADAAG 1991) / 32

Why the warning is placed at the platform edge / 32

Why the warning is 24 inches wide / 33

Width & placement decision also based on positive experience / 33

Detectable

warnings at curbramps, hazardous

vehicular ways &

reflecting pools

Requirement at curb-ramps / 34

Requirement at hazardous vehicular ways / 34

Requirement at reflecting pools / 34

Chapter 3. Recent Research on Detectable Warnings

Effect of curbramps on blind

pedestrians

Effect on street detection / 36

Effects of slope and placement / 36

Effects of detectable warnings on

blind pedestrians

Detectable warnings are helpful at curb-ramps / 37

Detectable warnings reduce falls at transit platform edges / 37
U.S. Access Board  Detectable Warnings: Synthesis 5

Contents  Detectable Warnings: Synthesis, continued

Effects of detectable warnings on

people with mobility

impairments

Effects on transit platforms / 38

Effects at slopes or curb-ramps / 38

Benefits at curb-ramps / 39

Effects at hazardous vehicular ways / 39

Evaluation of

detectable warning

materials

Laboratory testing / 40

Field testing / 41

Research on

sound on canecontact differences

A test of difference in sound / 42

Research on

visual contrast

Contrast of detectable warnings / 43

Research shows value of safety yellow / 43

Standards for safety yellow / 43

Research on

detectability

Many truncated dome surfaces / 44

Many truncated dome surfaces found to be highly detectable / 44

Factors which have little effect on detectability / 44

Factor which decreases detectability / 44

Research on

dome dimensions &

spacing

Japanese research / 45

Dome height tests / 45

Dome diameter and spacing tests / 45

Optimal dome diameter & spacing combinations / 45

Chapter 4. International Use of Warning Surfaces

Different

approaches

Tactile ground surface indicators / 48

TGSIs as a wayfinding system / 48

TGSIs to indicate a variety of features / 48

TGSIs for warnings & directional information / 49

U.S. approach to warning surfaces / 49

U.S. approach to directional surfaces / 49
6 U.S. Access Board  Detectable Warnings: Synthesis

Contents  Detectable Warnings: Synthesis, continued

Usage by country Japan / 50

United Kingdom / 52

Australia / 55

New Zealand / 58

Italy / 60

France / 62

Germany / 64

Austria / 66

Netherlands / 68

International

standardization

International Organization for Standardization (ISO) / 69

Technical Committee 173 (ISO/TC173) / 69

ISO draft on TGSIs / 69

Applications / 70

Installation of warning surfaces / 70

Chapter 5. U.S. Use of Detectable Warning Surfaces: Case Studies

Locating U.S.

installations of

detectable warning

surfaces

Developing a list of locations / 72

Mail survey / 72

Other information sources / 72

Responses to

mail survey

Responses to survey / 73

State & local requirements / 73

Interviews

regarding

detectable warning

installations

Interview / 74

Locating appropriate persons / 74

Types of locations for detectable warnings / 74

Interview locations City interviews / 75

Transit system interviews / 75

Other interviews / 75

Interview questions Interview questions / 76

Snow removal / 76
U.S. Access Board  Detectable Warnings: Synthesis 7

Contents  Detectable Warnings: Synthesis, continued

Interview results 

general

Materials / 77

Color of detectable warnings / 77

Installation dates / 77

Installation costs / 77

Installation method / 77

Interview results 

installation

problems

Installation problems or difficulties / 78

Interview results 

maintenance

General maintenance / 79

Snow & ice removal / 79

Interview results 

durability

Durability / 80

Interview results 

public reaction

Public reaction, problems or concerns / 81

No record of any lawsuits / 81

Lawsuits, but no details / 81

Case studies Austin, Texas / 82

Metropolitan Atlanta Rapid Transit Authority (MARTA) / 84

Roseville, California / 86

Metro North Railroad / 88

Harrisburg, Pennsylvania / 90

Massachusetts Bay Transportation Authority (MBTA) / 92

Cleveland, Ohio / 94

Baltimore County, Maryland / 96

Bay Area Rapid Transit (BART) / 98

Claremont, California / 100
8 U.S. Access Board  Detectable Warnings: Synthesis

Contents  Detectable Warnings: Synthesis, continued

Chapter 6. U.S. Use of Detectable Warning Surfaces: Applications

Sources of

recommendations

Purpose of this chapter / 102

ADAAG / 102

California Title 24 / 102

Project ACTION panel of experts / 103

Accessible Rights-of-Way: A Design Guide / 103

Designing Sidewalks & Trails for Access: Part II. A Best Practices 

Guidebook / 103

ACB Street Design Guidelines / 103

Roseville, CA / 104

Cambridge, MA / 104

Austin, TX / 104

Towson, MD / 104

AER resolutions / 104

ACB resolutions / 104

NFB resolutions / 104

Recommendations

for detectable

warnings at

curb-ramps

Whole surface of ramp  ADAAG / 105

Whole surface of ramp  California Title 24 / 106

Bottom 3 feet  Roseville, CA / 106

Bottom 2 feet  Multiple sources / 107

Parallel curb ramp / 108

Detectable warnings at hazardous

vehicular ways

California Title 24 / 109

Detectable

warnings at

medians & islands

Cut-through medians / 110

Cut-through splitter islands / 111

Detectable

warnings at raised

crosswalks & raised

intersections

Raised crosswalks & raised intersections / 112

Fitting to a blended curb at a raised intersection / 112
U.S. Access Board  Detectable Warnings: Synthesis 9

Contents  Detectable Warnings: Synthesis, continued

Chapter 7. U.S. Detectable Warning Products

Spacing of

truncated domes

Manufacturing standards / 114

ADAAG technical specification / 114

Brick pavers / 114

Pattern repetition / 115

Complementary tile pairs / 115

Working with irregular shapes / 115

Shape of

truncated domes

Truncated dome diameter / 116

Manufacturers’ response / 116

Types of detectable

warning products

Summary / 117

Use of term “detectable warning” / 117

Rely on current specifications / 117

Details should be verified / 117

Dimensional pavers Definition / 118

Natural stone, stone composites, & ceramic tile / 118

Brick pavers / 118

Large precast units / 118

Thin tiles &

sheet goods

Definition / 119

Rigid and flexible composition / 119

Tile size / 119

Installation / 119

On-site fabrication

of truncated dome

surfaces

Definition / 120

On-site production of domed surface / 120

Stamped concrete / 121

Detectable warnings that are not on grade / 121

Surface-applied dome products / 122
10 U.S. Access Board  Detectable Warnings: Synthesis

Contents  Detectable Warnings: Synthesis, continued

Characteristics of

detectable warning

products

Slip resistance / 123

Color / 123

Contrast / 123

Sound on cane-contact & resiliency / 124

Durability / 124

Detectable warning

product matrix

Matrix / 125

Photographs of

detectable warning

products

Sample photography / 126

16 photographs of product samples / 126

Detectable warning

manufacturers

List of manufacturer names and contact information / 132

Appendix

References and Annotated Bibliography / 136

Glossary / 147

Questionnaire for interviews regarding

detectable warning installations / 148
U.S. Access Board  Detectable Warnings: Synthesis 11

Introduction

Content of

synthesis

This synthesis summarizes the state-of-the-art regarding the design,

installation and effectiveness of detectable warning surfaces used in

the U.S. and abroad.

• The need for a warning surface is documented.

• U.S. and international research on detectable warnings is

reviewed.

• U.S. and international standards and guidelines for detectable

warnings are presented.

• Use of detectable warnings in the U.S. and abroad is described,

with illustrative case studies.

• Information is provided on U.S. detectable warning products

and manufacturers.

• Jurisdictional recommendations for the use of truncated dome

detectable warnings are summarized and illustrated.

Purpose of

synthesis

The synthesis was developed under contract to the U.S. Access Board.

It will be helpful to transportation engineers, planners, and other

interested persons working to make public rights-of-way more

accessible to people who have visual impairments.

Sources of

information

Information about detectable warning products and installations

comes from these sources:

• Information from the U.S. is based on input from individuals

representing public and private agencies or businesses that have

installed truncated dome detectable warnings.

• International information is based on input from individuals who

are familiar with the development and regulatory history of

warning surfaces in each country.

• Information on detectable warning products is based on interviews

with company representatives and on company literature.
12 U.S. Access Board  Detectable Warnings: Synthesis

FIG. 0-2. CURB RAMP COMPLYING WITH ADAAG 4.7.7

(TEMPORARILY SUSPENDED), CLEVELAND, OH.
U.S. Access Board  Detectable Warnings: Synthesis 13

Chapter 1



Background

Summary This chapter includes information on travel clues and cues used by

persons with visual impairments at curb-ramps and transit platform

edges. Early approaches to providing additional cues in Japan and the

United Kingdom are described. The results of U.S. programs of

research to identify detectable warning surfaces are summarized, and

U.S. standards are discussed.

Chapter contents This chapter covers the following topics.

 Topic Page

 How people who are blind detect streets 14

 Detecting transit platform edges 16

 Early solutions 17

 U.S. research to identify detectable warning

surfaces

18

 History of U.S. standards 21

 Other textured walking surfaces 26

 Truncated dome detectable warnings 27
14 U.S. Access Board  Detectable Warnings: Synthesis

How people who are blind detect streets

Curbs are a

definitive cue

The development of sidewalks and streets, with their identifying

curbs—the network of vehicular and pedestrian circulation—gave

pedestrians who were blind predictable environmental features that

could be used to maintain orientation and safety when traveling

independently.

Curbs designed to separate pedestrian from vehicular flow and to

provide a gutter edge to contain and direct water flow, provided a

reliable cue to pedestrians who were blind that they had arrived at an

intersecting street. Detection of a down curb unmistakably informed

blind pedestrians that they had come to the end of the sidewalk and

that their next step would be into the street.

How curbs are

detected

Detection techniques depend on the travel aids used by people who

are blind, such as long canes or dog guides, and their amount of

vision.

• People who are blind and use a long cane for a travel aid detect

a curb, or any other drop-off such as stairs or a platform edge,

by a change in the angle of the wrist and the failure of the cane to

contact the sidewalk at the expected level.

• People who use dog guides are alerted to the presence of a curb

or other drop-off when their dogs stop. They then confirm the

presence of the drop-off with a foot.

• People who have low vision, and do not use either a long cane or

dog guide, rely on differences in color or shading of the walking

surface. The sidewalk and street may have visual contrast, or the

curb material may contrast with the sidewalk or street.

There are a number of other sources of information about the location

of the curb indicating the end of the sidewalk (and the beginning of

the street) which may be used by any person having a visual

impairment, regardless of their travel aid or amount of low vision.

These include traffic sounds, the slope of the sidewalk, the end of a

building line, and changes in sun or wind. These are all simply clues

to the sidewalk/street boundary. None is a definitive cue.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 15

How people who are blind detect streets, continued

Elimination of curbs Accessibility requirements that were developed in the 1960s resulted

in the disappearance of curbs at many intersections. Curb-ramps,

blended curbs and depressed corners became common features.

Recently, raised crosswalks and intersections have been introduced

from Europe. Hotel, retail, airport, and other building entrances have

been designed without a curb separating them from street grade, for

easy access for pedestrians using wheeled luggage or carts, as well as

for persons with disabilities.

The need to rely on

multiple clues

In the absence of a definitive cue—the curbed sidewalk—at the

sidewalk/street boundary, it has become much more difficult for

pedestrians who are blind to detect streets. When blind pedestrians do

not detect a curb at the end of a block, they must rely on multiple

clues which, taken together, indicate the high probability that they

have come to a street.

They may detect a change in slope, which could be a curb ramp, a

change in terrain, or a broken sidewalk. The end of a building line or

grass line may suggest that there is a street directly ahead. Changes in

sun and wind are also clues. However, none of these clues, by itself,

confirms the presence of an intersecting street.

One of the most reliable clues, when it is present, is the sound of

traffic on the intersecting street. But in many locations, and at

different times of the day or days of the week, there may be little or no

traffic.

The difficulty of

finding and using

clues

Complex traffic operations, including actuated signals and right turn

on red, have made it increasingly difficult to analyze the environment

using vehicular sound. Large traffic volume and high ambient sound

often mask traffic flow and the sounds of vehicles starting and

stopping.

Blind pedestrians have become increasingly at risk in urban

environments where traffic flow information is complex, unclear,

masked by other sounds, or absent. The trend toward aggressive

driving has decreased the likelihood that drivers will stop for

pedestrians in crosswalks at unsignalized intersections, and the

general decline in pedestrian traffic has made it increasingly difficult

for blind travelers to obtain assistance for street crossings where

needed.

Continued on next page
16 U.S. Access Board  Detectable Warnings: Synthesis

Detecting transit platform edges

Techniques for

detecting transit

platform edges

having a drop-off

Detection techniques depend on the travel aids used by people who

are blind, and their amount of vision.

• People who are blind and use a long cane for a travel aid detect the

edge of a transit platform having a drop-off by a change in the

angle of the wrist and the failure of the cane to contact the

platform at the expected level. They must normally come to a stop

after taking no more than one step following the cane information.

• People who use dog guides are alerted to the presence of the

platform edge when their dogs stop. They then confirm the exact

location of the platform edge drop-off with a foot.

• People who have low vision, and do not use either a long cane or

dog guide, rely on differences in color or shading between the

platform and the track bed. Usually the platform is a lighter color

than the track bed, although the reverse may also be true.

Sometimes people having low vision are able to see a colored

safety line defining the end of the safe waiting area, and

sometimes illumination patterns may be helpful in determining the

location of the platform edge.

There are a number of other sources of information about the general

location of the platform edge, such as other riders waiting a safe

distance from the drop-off, and changes in air currents.

Blind people at risk

at transit platform

edges

Falling and fear of falling at high-level transit platform edges have

been found to be a major problem and cause of anxiety in blind transit

riders (Bentzen, Jackson & Peck, 1981).

In Bay Area Rapid Transit (BART) in San Francisco, during the ten

years before the installation of detectable warnings along platform

edges, approximately one fourth of all accidents along the edges of

raised platforms involved persons who were visually impaired

(McGean, 1991).
U.S. Access Board  Detectable Warnings: Synthesis 17

Early solutions

Japan

FIG 1-1. JAPANESE

TRANSIT PLATFORM

SHOWING DETECTABLE

WARNING AT THE TOP OF

STAIRS AND PARALLEL

TO THE PLATFORM EDGE,

AND A TACTILE PATH

LEADING FROM THE

STAIRS TO THE WAITING

AREA ALONG THE

PLATFORM.

Japan was the first country to make up for the information lost by

removal of curbs at intersections. Beginning in the 1960s the

Japanese installed a warning surface on curb-ramps that was

detectable both underfoot and by use of the long cane.

Warning surfaces at curb-ramps and blended curbs are now

commonplace throughout Japan. Warning surfaces are also used on

nearly all high-level transit platforms.

Surface texture

Most of the early Japanese surfaces intended to be warnings had a

surface configuration of domes about 5 mm high, which might be

somewhat flattened or truncated on top, arranged in a square pattern,

and having domes about 65 mm apart on center.

Placement, size, and material

Warning surfaces typically were placed on the lower end of curbramps, or along the former curb line where there were blended curbs.

Warning widths varied from about 30 mm to about 900 mm.

Materials used included rubber, stainless steel, cast pavers, and tiles.

On transit platforms, warning surfaces were commonly 300 mm wide

and placed about 900 mm back from platform edges. Warning

surfaces were used in conjunction with directional surfaces to form

networks of travel paths for persons who are visually impaired.

United Kingdom In the United Kingdom, a warning surface having a standardized

pattern of truncated domesreferred to as modified blister paving

has been recommended for use in specified locations and dimensions

since 1983 (Department of Transport, 1991; Gallon, Oxley & Simms,

1991; Textured pavements to help blind pedestrians, 1983).

These warnings can now be found throughout the United Kingdom on

curb-ramps and blended curbs. Most are cast pavers.
18 U.S. Access Board  Detectable Warnings: Synthesis

U.S. research to identify detectable warning surfaces

Extensive research

program on

detectability

An extensive program of research in the United States to identify

walking surfaces that could be used to alert people with visual

impairments to the presence of hazards such as streets and platform

edges began in 1980.

This research has been conducted by a number of researchers and

sponsored by

• the Federal Highway Administration,

• the Urban Mass Transportation Administration (now known as the

Federal Transit Administration),

• the Federal Transit Administration, and

• the U.S. Architectural and Transportation Barriers Compliance

Board (Access Board).

Importance of

under foot

detectability

Many tested surfaces have been found to be non-detectable or

minimally detectable; these are not appropriately considered to be

detectable warnings.

• It is essential that warnings be highly detectable under foot as well

as by use of the long cane.

• A minority of people who are legally blind regularly use a long

cane for obtaining surface information as they travel. Other people

who are visually impaired use dog guides or their low vision. To

detect changes in walking surfaces, they rely on visual contrast

and/or under foot information.

• Low vision is quite variable; a person who often can see streets,

platform edges and stairs may sometimes be unable to see them

because of glare, poor illumination, poor visual contrast, or fatigue.

• Many surfaces that seem likely to be highly detectable are only

somewhat detectable, especially under foot. Figure 1-2 shows a

number of surfaces that have been found to be minimally

detectable.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 19

U.S. research to identify detectable warning surfaces, continued

Early projects The earliest projects in the U.S. emphasized detection by blind

persons who were using a long cane, of a warning surface adjoining

brushed concrete.

• A ribbed rubber mat was found highly detectable to blind persons

using a long cane because it varied from concrete in texture,

resiliency and sound (Aiello & Steinfeld, 1980).

• A resilient tennis court surface was found to be highly detectable

to blind long cane users (Templer & Wineman, 1980).

• Various steel surfaces were found to be highly detectable on the

basis of differences in sound between steel and concrete when

contacted by a long cane used in a tapping technique (Templer,

Wineman & Zimring, 1982).

Surfaces for

transit platforms

A warning surface was needed for use on transit platforms, which was

highly detectable when it adjoined a variety of surfaces in common

use on platforms. The next series of projects addressed this need, and

identified two surfaces suitable for transit platform use, which were

both highly detectable when used in association with brushed

concrete, exposed aggregate concrete, rubber (Pirelli) tile, and heavy

wooden decking (Peck & Bentzen, 1987).

• A prototype “corduroy” surface having raised ribs which were

dome-shaped in cross section, 3/16 in high, 3⁄4 in wide, and 2 in

apart on center

• A resilient rubber tile having a truncated dome pattern (the pattern

that was the basis for the technical specification in the Americans

with Disabilities Act Accessibility Guidelines (ADAAG)

Both of these surfaces were more highly detectable in a noisy

environment than a rough textured steel surface or a resilient tennis

court surface. Both of these surfaces were highly detectable to blind

persons both under foot and with the use of a long cane.

The truncated dome surface was recommended for a standard warning

surface because similar surfaces were being used for warnings in

Japan and England. Linear surfaces were being used in Japan as

directional surfaces.
20 U.S. Access Board  Detectable Warnings: Synthesis

Surfaces with low detectability

2"

1/4"

2"

1/4" 1/4"

1/4"

1/16" 1/4"

1/4"

2"

1/4" 1/4"

2"

1/4" 1/4"

2" 2" 1/16"

1/4"

2" 1/16"

2" 1/16"

1/4"

FIG. 1-2. CROSS-SECTIONS OF SURFACES FOUND

TO BE LOW IN DETECTABILITY. DRAWN AT FULL SCALE.
U.S. Access Board  Detectable Warnings: Synthesis 21

History of U.S. standards

ANSI A117.1-1980—

Tactile warnings

In the 1980 ANSI (American National Standards Institute) Standard,

A117.1-1980 American National Standard: Specifications for Making

Buildings and Facilities Accessible to and Usable by Physically

Handicapped People, what were then referred to as tactile warnings

were specified for the entire walking surface of curb-ramps. A 36 in

(915 mm) wide strip was specified along the full edge of blended

curbs, and a tactile warning surface was also specified for tops of stair

runs except those in dwelling units, in enclosed stair towers, or to the

side of the path of travel. Further, tactile warnings were specified for

edges of reflecting pools that did not have railings, walls or curbs.

Tactile warnings were to be standardized within a building, facility,

site, or complex of buildings.

ANSI standards are voluntary consensus standards. ANSI A117.1-

1980 includes specifications for curb-ramps as well as tactile

warnings.

Specification of

texture

ANSI A117.1-1980 4.29.2

Tactile Warnings on Walking Surfaces. Tactile warning

textures on walking surfaces shall consist of exposed aggregate

concrete, rubber, or plastic cushioned surfaces, raised strips,

or grooves. Textures shall contrast with that of the

surrounding surface.... Grooves may be used indoors only.

ANSI A117.1-1986—

Detectable

warnings

ANSI A117.1-1986 American National Standard for Buildings and

Facilities—Providing Accessibility and Usability for Physically

Handicapped People, continued to specify the same warning textures,

by then called detectable warnings, on the full width and depth of

curb-ramps, at uncurbed intersections, at tops of stair runs, and at

reflecting pools.

Continued on next page
22 U.S. Access Board  Detectable Warnings: Synthesis

History of U.S. standards, continued

Implementation of

ANSI A117.1-1980

& 1986

Early implementations of the ANSI A117.1-1980 and ANSI

A117.1-1986 standard for tactile warnings included a number of

surface treatments such as grooved concrete, which were subsequently

found not to be highly detectable to pedestrians who are blind.

Grooved concrete is still used in some jurisdictions today, and it is

sometimes called a detectable warning although it has not been found

to be highly detectable and has not been recommended in any U.S.

standard for outdoor use.

The photos below illustrate a variety of curb ramp treatments that are

not now considered to be detectable warnings because they have not

been found to be highly detectable and are not standardized, or

because they are easily mistaken for other common features in the

pedestrian environment.

 

FIG. 1-3. A BLENDED CURB IN COLUMBUS, OH, WHICH USES DIFFICULTTO-DETECT ROWS OF RAISED BRICK.

 

FIG. 1-4. (LEFT) CURB RAMP WITH A MINIMALLY DETECTABLE GROOVED

SURFACE IN PHOENIX. FIG. 1-5 (RIGHT) A CURB RAMP WITH A NARROW

BORDER OF DETECTABLE WARNING PAVERS AT THE SIDES AND SMOOTH

PAVERS IN THE MIDDLE. BLIND PEDESTRIANS COULD EASILY MISS THE

NARROW BORDER OF DETECTABLE WARNING PAVERS.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 23

History of U.S. standards, continued

ADAAG (1991)—

Truncated dome

detectable warnings

In 1991, the Architectural and Transportation Barriers Compliance

Board (Access Board) published the Americans with Disabilities Act

Accessibility Guidelines (ADAAG), which included scoping and

technical specifications for truncated dome detectable warnings at

curb-ramps, hazardous vehicular ways, reflecting pools, and edges of

transit platforms having drop-offs. The ADAAG specifications are

provided in Chapter 2. The specifications were based on the extensive

program of research described above.

Controversy in the

U.S.

Both specifications and scoping for detectable warnings quickly

became one of the most controversial issues in ADAAG.

• 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 vehicular 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.”

CABO/ANSI

A117.1-1992—

Deleted detectable

warning

specifications

By 1992, some members of the ANSI A117.1 committee were no

longer certain that detectable warnings were needed in any location,

and all specifications for the texture and for its use in various locations

were dropped. There remained only the mention of standardization

within a building, facility, site, or complex of buildings.

Continued on next page
24 U.S. Access Board  Detectable Warnings: Synthesis

History of U.S. standards continued

Some ADAAG

requirements for

detectable warnings

suspended

Since April 1994, ADAAG requirements for truncated dome

detectable warnings at curb-ramps, hazardous vehicular ways and

reflecting pools have been temporarily suspended while the Access

Board has sought additional research on whether detectable warnings

are needed at curb-ramps and hazardous vehicular ways, whether

detectable warnings help people with visual impairments, and whether

detectable warnings have adverse impacts on people with mobility

impairments.

The requirement for truncated dome detectable warnings at transit

platform edges remains in effect.

Research on

detectable warnings

recommended

The requirement for detectable warnings at curb-ramps, hazardous

vehicular ways, and reflecting pools was suspended pending research

to determine

• Whether curb-ramps resulted in problems for pedestrians who are

blind,

• Whether detectable warning surfaces helped blind pedestrians, and

• Whether detectable warnings on curb-ramps had adverse impacts

on persons with mobility impairments.

See Chapter 3 for a summary of this research.

Rights-of-way

guidelines

In 1994 the Access Board proposed rights-of-way guidelines, Section

14, adapting the basic ADAAG 1-10 provisions for application to

public rights-of-way. However, Section 14 was not adopted as part of

the Department of Justice Standard for Accessible Design.

Accessible Rights of Way: A Design Guide published by the Access

Board in 1999, states: “Although no Federal scoping or technical

requirements have been established that apply specifically to public

rights-of-way, both ADAAG and UFAS [Uniform Federal

Accessibility Standards] contain technical requirements for the

construction of accessible exterior pedestrian routes that may be

applied to the construction of public rights-of-way. In the absence of

a specific Federal standard, public entities may also satisfy their

obligation by complying with any applicable State or local law that

establishes accessibility requirements for public rights-of-way that are

equivalent to the level of access that would be achieved by complying

with ADAAG or UFAS.”

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 25

History of U.S. standards, continued

Local and state

guidelines

Many state and local government agencies have adopted standards

that include specific recommendations intended to meet pedestrian

accessibility requirements. The following pedestrian guidelines were

reviewed to determine recommendations regarding the installation of

detectable warnings surfaces.

• Washington Pedestrian Facilities Guidebook

• Portland [Oregon] Pedestrian Design Guide

• Oregon Bicycle and Pedestrian Plan

• Florida Pedestrian Planning and Design Handbook

• Massachusetts Pedestrian Transportation Plan

• California Local Assistance Procedures Manual

Variety of

recommendations

All of these guidelines recommended some type of tactile warning

surface on curb-ramps. In addition, traffic-engineering professionals

from Arizona, Minnesota, Georgia, New Jersey and South Carolina

stated, in interviews, that there were state or local recommendations

for a surface change on the curb ramp.

• Portland, Oregon, and the States of Oregon, Washington, and

Florida guidelines all suggest a texture change on the curb ramp to

define the street edge for pedestrians who are visually impaired or

blind. However, a truncated dome surface is not required.

• The Oregon Bicycle and Pedestrian Plan recommends that a

diamond grid pattern be stamped on curb-ramps, and the Portland

Pedestrian Design Guide recommends that curb-ramps be finished

with heavy brooming parallel to the curb.

• California requires grooves around the top of the curb ramp,

truncated dome detectable warnings on the ramp surface where the

slope is lower than 1:15, and a 1⁄2 in beveled lip at the curb line.

• Other guidelines stated that a tactile warning was needed on the

curb ramp but gave no guidelines for surface type.

ICC/ANSI A117.1-

1998Equivalent

detectability

By 1998, based on recommendations of the ADAAG Review

Advisory Committee which had recently been submitted to the Access

Board for the revision of ADAAG, specifications for truncated dome

detectable warnings at platform edges were included in the ANSI

A117.1-1998 standard on accessibility. In this edition of ANSI

A117.1, the texture and visual contrast specifications were the same as

those in ADAAG.

Alternatively, equivalent detectability could be provided by other

means (ICC/ANSI A117.1-1998 705.3.2 and 705.3.3).
26 U.S. Access Board  Detectable Warnings: Synthesis

Other textured walking surfaces

Other surfaces A number of other textured surfaces are used on curb-ramps, but they

have not been demonstrated to be highly detectable to pedestrians who

are blind, both under foot and by the use of a long cane.

• Grooved cement has been found to be minimally detectable to

people using a long cane as a travel aid, and it is even less

detectable under foot.

• Other decorative surfaces that may be assumed to be detectable

have not been tested for detectability. Many surfaces that look

like they should be highly detectable have been found to be low in

detectability.

• Consistency in a warning surface is essential if it is to reliably be

understood as a warning by pedestrians with visual impairments.

• The truncated dome texture specified in ADAAG 4.29.2 is the

only surface that should be considered a detectable warning.

Raised design

flooring

Raised design flooring sold as sheet goods or resilient tile may have a

pattern of slightly raised circles. This product, sometimes known as

Pirelli tile, is not highly detectable and should not be considered a

detectable warning.

Directional tactile

paving

 

 

FIG. 1-6. DIRECTIONAL TACTILE

TILE (ARMOR-TILE)

 

FIG. 1-7. DIRECTIONAL TACTILE

TILE (DETECTABLE WARNING

SYSTEMS)

Some countries have specifications for a raised, directional texture to

guide people who are visually impaired. This texture is similar in

height and width to truncated domes, but is a linear element. Such a

directional texture should not be used as a warning.
U.S. Access Board  Detectable Warnings: Synthesis 27

Truncated dome detectable warnings

Focus on truncated

dome detectable

warnings

This publication uses the term “detectable warning” to mean the

walking surface consisting of truncated domes as specified in

ADAAG.

• The technical specification for detectable warnings in ADAAG is a

truncated dome surface.

• Truncated domes are the only texture that has repeatedly been

demonstrated to have excellent detectability to pedestrians who are

bind, both under foot and through the use of a long cane.

• Therefore, the primary focus of this synthesis is on truncated dome

detectable warnings. When the term “detectable warning” is used

in this synthesis, it always refers to a truncated dome surface.

FIG. 1-8. CURB-RAMPS

WITH TRUNCATED DOME

DETECTABLE WARNINGS

ON OPPOSITE SIDES

OF AN ALLEY,

CLEVELAND, OH.
28 U.S. Access Board  Detectable Warnings: Synthesis
U.S. Access Board  Detectable Warnings: Synthesis 29

Chapter 2



Detectable Warnings

in ADAAG

Summary This chapter presents specifications for detectable warning surfaces

as specified in the Americans with Disabilities Act Accessibility

Guidelines (ADAAG). It includes information on ADAAG technical

provisions for detectable warnings at transit platform edges, on curbramps, preceding hazardous vehicular ways, and surrounding

reflecting pools.

Chapter contents This chapter covers the following topics.

 Topic Page

 Definition & specification 30

 Geometry of detectable warnings 31

 Detectable warnings at transit platform edges 32

 Detectable warnings at curb-ramps, at hazardous

vehicular ways, and reflecting pools

34

 
30 U.S. Access Board  Detectable Warnings: Synthesis

Definition & specification

Definition of

detectable warnings

A detectable warning is:

A standardized surface feature built in or applied to walking

surfaces or other elements to warn visually impaired people of

hazards on a circulation path. ADAAG 3.5

Detectable warnings are unique and standardized features, intended to

function much like a stop sign. They alert pedestrians who are

visually impaired to the presence of hazards in the line of travel,

indicating that they should stop and determine the nature of the hazard

before proceeding further.

Specification for

detectable warnings

ADAAG specifies:

Detectable warnings shall consist of raised truncated domes

with a diameter of nominal 0.9 in (23 mm), a height of

nominal 0.2 in (5 mm) and a center-to-center spacing of

nominal 2.35 in (60 mm) and shall contrast visually with

adjoining surfaces, either light-on-dark or dark-on-light.

The material used to provide contrast shall be an integral

part of the walking surface. Detectable warnings used on

interior surfaces shall differ from adjoining walking surfaces

in resiliency or sound-on-cane contact. ADAAG 4.29.2

Visual contrast The appendix to ADAAG recommends that detectable warnings

contrast visually with adjoining surfaces.

The material used to provide contrast should contrast

by at least 70%. Contrast in percent is determined by:

Contrast = [(B1 – B2)/B1] x 100

where B1 = light reflectance value (LRV) of the lighter area

and B2 = light reflectance value (LRV) of the darker area.

Note that in any application both white and black are never

absolute: thus, B1 never equals 100 and B2, is always greater

than 0. ADAAG A4.29
U.S. Access Board  Detectable Warnings: Synthesis 31

Geometry of detectable warnings

Dome alignment

& pattern

The detectable warning surface

consists of truncated domes on a

square pattern which are typically

arranged in either of two

configurations:

• Diagonal alignment

• Parallel alignment

Figure 2-1 illustrates how both

configurations can comply with

the ADAAG specification for

detectable warning.

Depending on which configuration is used, the rows of domes

will be aligned with, or at a 45°

angle to:

• the curb or platform edge

• the direction of travel

Pedestrians encountering either

configuration will find the surface

pattern equally detectable.

Another acceptable and plausible

arrangement of truncated domes

uses an equilateral triangular grid.

Only one U.S. manufacturer has

ever chosen to produce a detectable warning surface using this

pattern.

FIG. 2-1. PATTERNS AND

ALIGNMENTS OF TRUNCATED

DOMES COMPRISING THE ADAAG

DETECTABLE WARNING.

2.35

60

2.35

60

0.9

23

0.9

23

0.9

23

2.35

60

2.3

60

5

2.35

60

2.35

60 Direction of travel

Square pattern,

diagonal alignment

Square pattern,

parallel alignment

Triangular pattern

Dome profile

FIG. 2-2. HEIGHT AND DIAMETER

 OF TRUNCATED DOMES USED IN

ADAAG DETECTABLE WARNING.

 

0.9

23

0.2

5
32 U.S. Access Board  Detectable Warnings: Synthesis

Detectable warnings at transit platform edges

Requirement

for transit

platform edges

(ADAAG 1991)

FIG. 2-3. DETECTABLE

WARNING USED AT

PLATFORM EDGE

BORDERING A

DROP-OFF.

Platform edges bordering a drop-off and not protected by

platform screens or guardrails shall have a detectable

warning. Such detectable warnings shall comply with

[ADAAG] 4.29.2 and shall be 24 inches wide running the full

length of the platform drop-off ` ADAAG 10.3.1(8)

This requirement is applicable to new construction, alteration, and in

key stations in existing transit facilities.

Railway or transit platform

24

610

Detectable warning

Low

trackbed level

High

platform level

Why the warning

is placed at the

platform edge

The rationale for placement of detectable warnings as required by

ADAAG was as follows.

• Advocates wanted the warning to be at or very near the platform

edge so that there would be no possibility that a traveler could

interpret a width of platform between the warning and the edge as

a safe place to stand.

• Transit managers wanted the warning to be at the edge so that on

platforms that were retrofitted with detectable warnings, there

would be sufficient platform width on the side away from the edge

to accommodate a typical rush hour number of riders without the

necessity for riders to stand on the warning due to crowded

conditions.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 33

Detectable warnings at transit platform edges, continued

Why the warning

is 24 inches wide

The rationale for the width of detectable warnings required by

ADAAG was the following.

• 24 in (610 mm) had been repeatedly demonstrated to be a

sufficient width of a surface highly detectable both under foot and

by use of a long cane, to enable detection and stopping on that

surface by most blind travelers (Peck & Bentzen, 1987; Templer

& Wineman, 1980; Templer, Wineman & Zimring, 1982).

• Transit managers wanted the warning to be as narrow as possible.

They did not want riders to either stand and wait on the warning,

or travel on it while no train was at a platform. Therefore a

warning surface needed to:

 reduce the effective standing capacity of platforms

as little as possible;

 enable blind passengers to stop a safe distance from

the platform edge without having to contact the edge

to determine where it was; and

 demarcate the limit of the safe waiting area for all passengers.

Transit managers reasoned that while most passengers would wait

behind the warning most of the time, there would nonetheless be a

small minority of passengers who would choose to walk along the

warning, between the edge and waiting passengers, if the warning was

wider than 24 in (R. Weule, BART Safety Manager, personal

communication, 1986).

Width & placement

decision also

based on positive

experience

FIG. 2-4. DETECTABLE

WARNING SURFACE AT

MARTA STATION,

ATLANTA, GA.

Also contributing to the rationale

for ADAAG specifications

regarding both width and

placement of detectable warnings

on transit platform edges was a

decrease in accidents for all riders

on BART (McGean, 1991) and

Metro Dade (A. Hartkorn, Metro

Dade Safety Manager, personal

communication, 1994) in the

years following installation of

24 in wide detectable warnings at

platform edges in those systems.
34 U.S. Access Board  Detectable Warnings: Synthesis

Detectable warnings at curb-ramps,

hazardous vehicular ways and reflecting pools

Requirement

at curb-ramps

FIG. 2-5. FLORIDA

CURB RAMP COMPLYING

WITH ADAAG 4.7.7.

A curb ramp shall

have a detectable

warning complying

with [ADAAG] 4.29.2.

The detectable warning shall extend the full

width and depth of the

curb ramp.

ADAAG 4.7.7.

(Temporarily suspended

April 12, 1994, July 29,

1996, and November 23,

1998)

Requirement

at hazardous

vehicular ways

FIG. 2-6. EXAMPLE

OF DETECTABLE

WARNING AT A LEVEL

RAIL CROSSING

(A TYPE OF HAZARDOUS

VEHICULAR WAY).

If a walk crosses or adjoins a vehicular way, and the walking

surfaces are not separated by curbs, railings or other elements

between the pedestrian areas and vehicular areas, the boundary

between the areas shall be defined by a continuous detectable

warning which is 36 in (915 mm) wide, complying with 4.29.2

ADAAG 4.29.5 (Temporarily suspended April 12, 1994, July 29,

1996, and November 23, 1998)

Requirement at

reflecting pools

The edges of reflecting pools shall be protected by railings,

walls, curbs, or detectable warnings complying with

[ADAAG] 4.29.2.

ADAAG 4.29.6 (Temporarily suspended April 12, 1994, July 29,

1996, and November 23, 1998).
U.S. Access Board  Detectable Warnings: Synthesis 35

Chapter 3



Recent Research on

Detectable Warnings

Summary This chapter summarizes research to answer questions about the need

for and effectiveness of detectable warnings for people who are blind

or visually impaired and the effects of detectable warnings on

pedestrians with mobility impairments. The chapter then describes

research on visual contrast and sound contact. It concludes with

further research on detectability and discriminability conducted in

Japan and the United Kingdom.

Chapter contents This chapter covers the following topics.

 Topic Page

 Effects of curb-ramps on blind pedestrians 36

 Effects of detectable warnings on travel by blind

pedestrians

37

 Effects of detectable warnings on people with

mobility impairments

38

 Evaluation of detectable warning materials 40

 Research on sound on cane-contact differences 42

 Research on visual contrast 43

 Research on detectability 44

 Research on dome dimensions and spacing 45
36 U.S. Access Board  Detectable Warnings: Synthesis

Effects of curb-ramps on blind pedestrians

Effect on street

detection

Two research projects (Barlow & Bentzen, 1994; Bentzen & Barlow,

1995; Hauger, Safewright, Rigby & McAuley, 1994) confirmed that

removal of the single reliable cue to the presence of an intersecting

street, that is, the down curb, did result in the inability of even skilled,

frequent blind travelers to detect some streets.

Barlow and Bentzen found that on 35% of approaches to unfamiliar

streets, blind travelers using a long cane failed to detect the presence

of an intersecting street before stepping into it. Hauger et al. found

failure to detect streets on a somewhat smaller percentage of trials.

Effect of slope &

placement

FIG. 3-1. WHERE THERE

IS NO DIFFERENCE IN

SLOPE OR ELEVATION

BETWEEN THE SIDEWALK

AND STREET, IT IS PARTICULARLY DIFFICULT FOR

PEDESTRIANS WHO ARE

BLIND TO DETERMINE

WHEN THEY HAVE

REACHED AN INTERSECTING STREET.

BLENDED CURB IN

SACRAMENTO, CA.

Both projects (Barlow & Bentzen, 1994; Hauger et al., 1994) found

that failure to detect streets was highly correlated with slope of the

curb ramp. Barlow and Bentzen also found that street detection was

correlated with the abruptness of change in angle between the

approaching sidewalk and the curb ramp.

Both projects found that street detection was more likely when curbramps were at the apex of a corner than when they were in the line of

travel. Hauger et al. also found that apex curb-ramps were more

likely to lead to unsuccessful street crossings than perpendicular curbramps.
U.S. Access Board  Detectable Warnings: Synthesis 37

Effects of detectable warnings

on travel by blind pedestrians

Detectable

warnings are

helpful at curbramps

Hauger et al. (1994) obtained subjective data from 70 research

participants who were blind or who had low vision, indicating that

detectable warnings were judged to be helpful.

In the same project, raters viewing videotapes of the 70 participants as

they crossed intersections with and without detectable warnings on

curb-ramps, found that a higher proportion of unsuccessful crossings

occurred where there were no detectable warnings than where there

were detectable warnings.

They also found that the visual contrast of detectable warnings helped

participants with low vision establish and maintain a heading toward

the opposite corner. Participants using dog guides may also have been

aided by the visual contrast that the dog guides appeared to head for.

Hughes (1995) conducted research in which 17 participants who were

totally blind or who had low vision traveled up and down laboratory

ramps having eight different tactile surfaces, of which five were

truncated domes. Ten of the participants then responded to structured

interviews including questions about their perception of the tactile

surfaces. Nine said use of tactile surfaces on curb-ramps would

increase their safety. Six said that use of the tactile surfaces would

make them more likely to travel by foot.

Detectable

warnings reduce

falls at transit

platform edges

During the seven years following the installation of detectable

warnings on all platform edges in the BART system, platform edge

accidents decreased for all riders, but especially for riders having

visual impairments (McGean, 1991).

• In San Francisco, riders in stations having different platforms

serving both BART and Muni (San Francisco Municipal Railway)

were observed to stand at different distances from the platform

edge.

• On BART platforms, which had 24 in detectable warnings along

the edges, passengers tended to wait behind the warning, that is, at

least two ft from the edge.

• On MUNI platforms, which did not have detectable warnings,

passengers waited closer to the edge (McGean, 1991).
38 U.S. Access Board  Detectable Warnings: Synthesis

Effects of detectable warnings on

people with mobility impairments

Effects on transit

platforms

Objective and subjective research confirm that truncated dome

detectable warnings at transit platform edges do not adversely affect

people having a variety of mobility impairments.

• None of the 24 participants in research by Peck and Bentzen

(1987) in BART had any difficulty maneuvering across or along

truncated domes or turning on truncated domes.

• Participants in this Peck and Bentzen research reported that

truncated domes would have minimal effects on their travel in

BART. A few people who used canes or crutches said they felt

their aids would be less likely to slip as they exited trains onto the

truncated dome surface than onto smoother surfaces.

Effects

at slopes or

curb-ramps

 Objective and subjective research confirm that truncated dome

detectable warnings on slopes or curb-ramps have minimal adverse

effects on people with mobility impairments.

• Bentzen, Nolin, Easton, Desmaris and Mitchell (1993, 1994b)

videotaped 40 participants having those mobility impairments

which made them most likely to have difficulty on bumpy, sloping

surfaces, travel up and down, stopping, starting, and turning on

seven ramps (slope 1:12) having nine different truncated dome

surfaces and one ramp surfaced with brushed concrete. Video

raters observed minimal evidence of increased effort, slipping, loss

of stability, or wheel or tip entrapment on this challenging task.

• Participants in this Bentzen et al. (1993, 1994b) research reported

minimal effects of truncated domes relative to the brushed

concrete surface.

• Hughes (1995) had nine people with mobility impairments travel

up and down eight ramps with different tactile surfaces. No

individuals reported or were observed to have problems with

directional control, stability, effort or discomfort that would have

altered their ability to travel safely.
U.S. Access Board  Detectable Warnings: Synthesis 39

Effects of detectable warnings on

people with mobility impairments, continued

Benefits at

curb-ramps

FIG. 3-2. STAMPED

CONCRETE DETECTABLE

WARNING ON CURB

RAMP, AUSTIN, TX.

Hauger et al. (1994) had 30 participants with mobility impairments

travel up and down curb-ramps with and without truncated domes.

• A majority felt that they were safer, had better traction, and were

more stable on ramps having truncated domes than on concrete

ramps.

• Forty four percent of participants said it required less effort to

negotiate up and down the ramps with detectable warnings than

the concrete curb-ramps; 23% said the reverse.

• Some wheelchair users said it was easier to find and steer toward

the up-ramp on the opposite corner when it had the contrasting

detectable warning surface.

Effects at

hazardous

vehicular ways

Hauger et al. (1994) observed pedestrians at three commercial sites

where shopping carts were used and where detectable warnings were

installed to separate the pedestrian and vehicular ways. In 12 hours of

observation, more than 1,500 pedestrians crossed the detectable

warnings. No significant incidents or problems were observed for the

general public, which included persons with mobility impairments,

shopping carts, shopping carts with children, large gurneys, and baby

carriages.
40 U.S. Access Board  Detectable Warnings: Synthesis

Evaluation of detectable warning materials

Laboratory testing Eighteen truncated dome materials were submitted to laboratory

testing under a project sponsored by the Federal Transit

Administration (Ketola, N. & Chia, D., 1994). Standard tests were

performed for impact resistance, wet and dry slip resistance, wear

resistance, high-pressure hot water resistance, and adhesion/bond

strength after 55 hours soaking in water.

• Impact tests under room temperature, hot and cold conditions

found that, in general, rubber-based and polymer composite

materials performed quite well; more rigid products

(cementitious or ceramic tile) performed poorly.

• All materials exceeded the minimum value for slip resistance

recommended by the Access Board under both wet and dry

conditions.

• Wear resistance tested by 30 seconds of sandblasting revealed

a wide variety in performance of materials.

• High pressure hot water testing revealed little difference among

products.

• Seven materials were found to have poor adhesion/bond strength.

Detailed results of laboratory testing are in Ketola and Chia, 1993.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 41

Evaluation of detectable warning materials, continued

Field testing Eight of the surfaces subjected to laboratory testing were field tested

in high pedestrian traffic indoor and outdoor areas in stations of three

rail transit systems, the MBTA (Boston), GCRTA (Cleveland), and

SEPTA (Philadelphia) (Ketola & Chia, 1994). Evaluations included

installation and maintenance, wear resistance, maintenance of bond,

resistance to cracking and chipping, and maintenance of color.

• Proper installation was found to be crucial to good performance.

Factors affecting adequacy of installation included installer skill,

ambient conditions, surface preparation, application of material

and setting period.

• No transit system reported maintenance problems with any

material.

• No transit system reported any difficulty removing snow and ice

from any materials using the same tools and chemicals used on the

rest of the platform surface.

• Although materials differed in wear resistance, all were estimated

to have a relatively long useful life.

FIG. 3-3. INSTALLATION

OF DETECTABLE WARNING TEST SURFACES

AT MBTA’S SOUTH

STATION, BOSTON, MA.

• Materials differed widely in

maintenance of bond; four

materials had some bond

failure.

• Materials differed greatly in

resistance to cracking and

chipping; two materials had

no instances of cracking and

chipping, and two had

repeated instances.

• Three materials showed no

color change indoors or

outdoors; one material

showed major color change.
42 U.S. Access Board  Detectable Warnings: Synthesis

Research on sound on cane-contact differences

A test of difference

in sound

Although ADAAG 4.29.2 requires that detectable warning surfaces

used indoors differ in sound on cane-contact, there has been no

attempt to quantify the amount of difference in sound. Bentzen and

Myers (1997) did, however, test four truncated dome products

installed on an outdoor light rail platform in Sacramento for

differences in sound on cane-contact.

• Surfaces differed from one another in both objective and

subjective measures of differences in sound on cane-contact

between the adjoining platform of pavers and the detectable

warnings.

• Difference in sound between the warning surface and the

adjoining platform surface appears to be related to both the

detectable warning material and the way in which it is installed.

• The detectable warning material installed with a slight gap

between the warning and the substrate was most detectable on

both objective and subjective measures.
U.S. Access Board  Detectable Warnings: Synthesis 43

Research on visual contrast

Contrast of

detectable warnings

ADAAG 4.29.2 requires that detectable warnings contrast visually

with adjoining surfaces, either dark on light, or light on dark.

A 70% contrast in light reflectance between a detectable warning and

an adjoining surface is recommended in the Appendix (A4.29.2).

Research

shows value of

safety yellow

Recent research indicates that the color safety yellow is so salienteven to persons having very low vision-that it is highly visible even

when used in association with surfaces having light reflectance values

differing by as little as 40% (new, gray-white concrete) (Bentzen,

Nolin, and Easton, 1994a).

• A safety yellow detectable warning surface having a 40%

reflectance difference from new concrete was subjectively judged

more detectable than a darker warning surface which contrasted

with new concrete by 86% (Bentzen et al., 1994a).

• Hughes (1995) found that yellow or yellow-orange warning

surfaces were preferred over black warning surfaces.

Standards for

safety yellow

Safety yellow is a color that is standardized for use as a warning

in the pedestrian/highway environment.

• U.S. ANSI Z535.1-1991, 6.3

• Internationally—ISO 3864-1984(E)
44 U.S. Access Board  Detectable Warnings: Synthesis

Research on detectability

Many truncated

dome surfaces

Following publication of ADAAG in 1991, numerous manufacturers

entered the market. The products differed slightly in execution of the

truncated dome dimensions and spacing as well as materials (see

Chapter 7).

Truncated dome products soon included resilient sheet material,

dimensional pavers, tiles, polymer composites, bricks, pre-cast

concrete, stamped concrete and applied surfaces.

Many truncated

dome surfaces

found to be highly

detectable

In 1994 the Federal Transit Administration sponsored laboratory

research (Bentzen, Nolin, Easton, Desmarais & Mitchell, 1994) to

evaluate the detectability of truncated dome surfaces that differed in

material, dome dimensions, and dome spacing.

• 13 surfaces representing the extremes as well as the midpoints of

dome dimensions and dome spacing were tested by 24 blind

participants for under foot detectability in association with four

transit platform surfaces varying in roughness and resiliency.

• Each detectable warning surface was paired with brushed concrete,

coarse exposed aggregate concrete, Pirelli tile, and wooden

decking.

• Detection rate was greater than 95% for all but one warning

surface (a prototype that was not offered for sale).

Factors which have

little effect on

detectability

A number of factors were found to have little or no effect on

detectability.

• Parallel vs. diagonal alignment of domes

• Differences in resiliency

• Additional small elements added to increase slip resistance

• Irregularities in spacing where domes in adjoining tiles or pavers

were somewhat closer together or farther apart than within the tiles

or pavers

• A gradual increase in dome height within the first several inches

Factor which

decreases

detectability

Detectability of truncated dome warning surfaces was less when the

warning was installed in association with coarse exposed aggregate

concrete.
U.S. Access Board  Detectable Warnings: Synthesis 45

Research on dome dimensions and spacing

Japanese research Dome (raised dot) height, diameter and spacing were investigated to

determine optimal dome dimensions and spacing. (Report of

fundamental research on standardization relating to tactile tiles for

guiding the visually impaired, 1998).

• For testing dome height, 60 participants walked from smooth tiles,

across domed tiles of different heights, and were asked to report

whether they detected a domed tile under foot.

• For testing dome diameter and spacing, 60 blind participants

walked from smooth tiles, across either domed tiles or directional

(bar) tiles having different dimensions, and reported whether tiles

had domes or a directional (bar) pattern. (See Fig. 4-3 for the

nine diameters and spacings tested.)

• Participants also rated tiles for ease of identifying them as either

dome or directional tiles.

Dome height tests Dome heights tested were 0 mm, 2.5 mm, 5.0 mm, 7.5 mm and

10 mm.

• All participants detected tiles having 5.0 mm high domes.

• 15% of participants could not detect tiles having 2.5 mm high

domes.

• Some participants stumbled when traversing tiles having 10 mm

high domes.

• 5.0 mm high domes were recommended.

Dome diameter and

spacing tests

Dome base diameters tested were (22 mm, 28 mm, and 35 mm), and

dome spacings were (42.9 mm, 50 mm, and 60 mm). Top diameter of

domes was always 10 mm less than bottom diameter. Dome spacing

was measured on centers parallel to one side of a square pattern.

Optimal dome

diameter and

spacing

combinations

Three tiles had identification rates greater than 90% and were also

rated easy to identify:

• 22 mm base diameter with 50 mm spacing;

• 22 mm base diameter with 60 mm spacing; and

• 28 mm base diameter with 60 mm spacing.
46 U.S. Access Board  Detectable Warnings: Synthesis

Illustrations of international tactile ground surface indicators

3-4. WARNING PAVERS

AT A RAISED

CROSSWALK. UNITED

KINGDOM.

FIG.3-5. DETECTABLE

WARNING AT TOP &

BOTTOM OF STAIRS,

EXTERIOR USE IN

AUSTRALIA.

FIG. 3-6. (LEFT)

DETECTABLE WARNINGS

(BLISTER SURFACE) ON

THE THREE CURB-RAMPS

AT A SPLITTER ISLAND,

IRELAND

FIG. 3-7. (RIGHT)

TACTILE GROUND

SURFACE INDICATORS

LEADING AWAY FROM

STAIRS, LOUVAIN,

BELGIUM.
U.S. Access Board  Detectable Warnings: Synthesis 47

Chapter 4



International Use of Warning Surfaces

Summary This chapter includes information on approaches to use of tactile

ground surface indicators, including warning surfaces. Information on

selected countries having significant experience in the application of

warning surfaces is presented. Each entry includes the history,

specifications or guidelines for textures and locations, maintenance

and durability, and acceptance.

Chapter contents This chapter covers the following topics.

 Topic Page

 Different approaches 48

 Japan 50

 United Kingdom 52

 Australia 55

 New Zealand 58

 Italy 60

 France 62

 Germany 64

 Austria 66

 Netherlands 68

 International standardization 69

Common

conversions

(inches are

rounded figures)

5 mm

25 mm

50 mm

60 mm

= 0.2 in

= 1 in

= 2 in

= 2.35 in

100 mm

200 mm

300 mm

500 mm

= 4 in

= 8 in

= 12 in

= 20 in

600 mm

1200 mm

1800 mm

2 m

= 24 in

= 47 in

= 71 in

= 79 in
48 U.S. Access Board  Detectable Warnings: Synthesis

Different approaches

Tactile ground

surface indicators

Worldwide, a number of ground or floor surfaces have been used to

provide different types of information to people who have visual

impairments. In the work of the International Organization for

Standardization (ISO), these surfaces are referred to as tactile

ground/floor surface indicators or TGSIs.

TGSIs as a

wayfinding system

FIG 4-1. “ATTENTION

FIELD” SURFACE SHOWN

CIRCLED HERE, AND IN

FIG. 4-2.

FIG. 4-2. WAYFINDING

SYSTEM OF LINEAR

SURFACES AND

ATTENTION FIELDS IN

AUSTRIAN SUBWAY

SYSTEM.

In many countries, TGSIs are conceptualized as providing a

comprehensive wayfinding system for people with visual

impairments. In implementing this approach, extensive use is made of

linear surfaces that provide guidance from one place to another such

as between the stairs and the platform edge in a transit station.

Surfaces that are similar to the detectable warning surface in the U.S.

are designated as “attention fields,” and are typically used at path

intersections, at curb-ramps(especially mid-block), or at turns, as well

as at platform edges and curb-ramps. Japan, Austria, Switzerland,

France and Italy take this approach.

TGSIs to indicate a

variety of features

In the United Kingdom, seven different tactile ground or floor

surfaces are used to help people who are visually impaired recognize

different types of features in the environment. Different surfaces are

used to indicate crossing points (curb-ramps), hazards (steps, ramps,

entrances to transit platforms), indoor transit platform edges, outdoor

transit platform edges, segregated shared bicycle/pedestrian surfaces,

and amenities such as public telephones and ticket offices. A linear

surface is also used as a guidance path.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 49

Different approaches, continued

TGSIs for warnings

& directional

information

Some countries, including Australia, New Zealand and Canada use

warning surfaces (truncated domes) only where there are vehicular

hazards or drop-offs.

They also use linear directional surfaces where directional cues such

as grasslines, curbs, hedges, fences, or walls are not present.

U.S. approach to

warning surfaces

In the U.S., (although opinions vary), the prevailing attitude as

articulated in standards and guidelines, is that warning surfaces are

needed

• primarily at highly hazardous locations where there is no

definitive cue denoting the boundary between pedestrian and

vehicular ways (curb-ramps and hazardous vehicular ways), or

• where there is a drop-off (platform edges, reflecting pools and

stairs).

It is recognized that people who are blind are usually able to negotiate

these hazards safely, using their normal travel aids-such as long canes

or dog guides-especially when they are in familiar areas.

Detectable warnings can provide information about the presence,

location and direction of hazards that is useful to blind pedestrians

traveling in unfamiliar places. Detectable warnings can also provide

confirming cues about the environment for pedestrians who may not

have highly developed travel skills.

U.S. approach to

directional surfaces

There has been limited use of directional surfaces in the U.S. for such

purposes as guidance across wide or skewed intersections, or guidance

to a curb ramp. Most of this experience has been in San Francisco,

Sacramento and San Diego, CA. No standards or guidelines have ever

been established in the U.S. for the use of directional surfaces.

In the U.S. it is not considered necessary to provide a comprehensive

tactile wayfinding system for people who have 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.
50 U.S. Access Board  Detectable Warnings: Synthesis

Japan

History of use

 

Tactile warning and guidance surfaces have been used in Japan

since 1967.

• Use began in Okayama Prefecture and is now widespread

throughout Japan

• Used on platforms and top and bottom of stairs in almost

100% of transit station in metropolitan areas

• Also used at curb-ramps and on sidewalks

• There is on-going research to determine optimal dimensions for

truncated dome warning and linear directional surfaces

(Murakami, Aoki, Taniai, & Muranaka, 1982; Murakami, Ohkura,

Tauchi, Shimizu, & Ikegami, 1991; Report of fundamental

research on standardization..., 1998)..

Most common

texture

Texture not standardized; dome shape, diameter and spacing varies.

This is the most common texture.

• Dome height—5 mm (all warning surfaces)

• Dome base diameter—35 mm

• Inter-dome spacing—50 mm with parallel or diagonal alignment

Guidelines for

location of warning

surfaces

From Guidelines for Installation of Tactile Guide Blocks for the

Visually Impaired and Commentary (1985). These are guidelines

only; dimensions are given in only a few instances, but there are

numerous illustrations.

• Curb-ramps—600 mm deep, about 300 mm from the street, the

full width of the associated crosswalk

• Islands—on islands wherever a crosswalk contacts an island, 600

mm deep, about 300 mm from the street, the full width of the

associated crosswalk

Products Products used for warning surfaces are:

• Stone

• Concrete

• Synthetic rubber

• Plastic resin

• Vinyl chloride

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 51

Japan, continued

Durability and

maintenance

Durability and maintenance of warning surfaces are not considered

problems in Japan.

• Heavily traveled warning surfaces wear out regardless of the

material.

• Color changes, splitting of tiles, falling off of tiles, and

deterioration of domes sometimes occur.

• Snow and ice area not normally removed.

• Synthetic rubber and vinyl chloride are very slippery when wet.

Acceptance Warning and guidance surfaces are well accepted in Japan.

• Many Japanese persons with visual impairments depend on

warning and guidance surfaces.

• Persons with mobility impairments accept them.

• There are few complaints from persons who are elderly.

• There are few complaints from bicyclists.

Information

provided by

Masaki Tauchi, Ph.D.

Okayama Prefectural University

111 Kuboki, Soja-shi

Okayama 719-11, Japan

Tel: +81 866-94-2188

Fax: +81 866-94-2206

E-mail: mtauchi@fhw.oka-pu.ac.jp

Japanese research

on detectable

warnings

FIG. 4-3. JAPANESE RESEARCH

VARIED THE SIZE OF TRUNCATED

DOMES (DOT DIAMETER) AND THE

SPACING INTERVAL BETWEEN

DOMES (DOTS).

OF THE NINE DETECTABLE

WARNING TEST SURFACES, THREE

(SHOWN ENCLOSED BY THE LINE)

WERE IDENTIFIED AS DOT (VERSUS

BAR) TILES ON AT LEAST 90% OF

TRIALS.
52 U.S. Access Board  Detectable Warnings: Synthesis

United Kingdom

History of use

 

Domed warning (blister) surfaces have been used on curb-ramps and

at at-grade crossings in the UK since 1986.

• Domed surface for warning changed to truncated dome surface

because it was more comfortable, particularly for persons with

mobility impairments associated with arthritis

• Extensive research program conducted on detectability,

discriminability and memory for seven different tactile paving

surfaces to provide a warning at curb-ramps, at stairs and ramps, at

off-street transit platform edges, and at on-street transit platform

edges, to provide guidance along a route, to provide information

about a segregated cycle/pedestrian way, and to provide

information about the location of amenities such as public

telephones (Gallon, 1992; Gallon, Oxley & Simms, 1991; Savill,

Davies, Fowkes, Gallon & Simms, 1996; Savill, Stone & Whitney,

1998).

Texture Specifications for the blister surface and its use first were adopted in

1986. They were revised in 1991 (Disability Unit Circular 1/91).

• Dome height—5 mm ± .5 mm

• Dome base diameter—25 mm

• Domes 64-67 mm apart with parallel alignment.

Locations of tactile

paving surfaces

Extensive guidance on the location and installation of six different

tactile paving surfaces is contained in Guidance on the use of tactile

paving surfaces (1998), which supercedes Disabilitiy Unit Circular

1/91). Each surface is to be used for a different purpose.

• Pedestrian crossing points where the sidewalk is flush with the

street

• Hazards including stairs, level crossings and the approach to light

rapid transit platforms

• The edge of off-street rail platforms

• The edge of on-street rail platforms

• A shared cycle track/footway surface and central delineator strip

• Guidance along a route where traditional cues such as property

lines or curbs are not available

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 53

United Kingdom, continued

Warning surface at

curb-ramps,

medians, and raised

crosswalks

“It is vitally important

that the removal of any

existing kerb upstand

at a recognized

crossing point, is

accompanied by the

installation of the blister

surface.” Guidance on

the Use of Tactile

Paving Surfaces (1998)

Guidance on the installation of truncated domes (blister surface) on

curb-ramps, medians, and raised crosswalks is as follows.

• Depth of installation varies with nature of crossing, 400-1200 mm

across curb ramp, with stem (1200 mm wide) to the building line

at signalized crossings

• On medians >2 m wide, warning surface required for depth of 800

mm at each side

• On medians <2 m wide, warning surface required for entire depth

of median

• On the sidewalk at both ends of raised crosswalks.

• Red normally used at signalized crossings

• Buff (or any color other than red, which contrasts with

surrounding pavement) normally used at unsignalized crossings

Warning surface at

off-street transit

platform edges

Specifications for truncated domes and guidance on their installation

on off-street transit platform edges are as follows.

• Dome height—5 mm ± 0.5 mm

• Dome base diameter—22.5 mm

• Installation—400 mm deep, installed 500-700 mm from platform

edge

Other warning

surfaces

Two additional warning surfaces are recommended for other purposes.

• At on-street platform edges: a surface comprised of small raised

lozenge shapes running in the direction of the platform edge is

installed at a depth of 400 mm, 500-700 mm from the platform

edge.

• At stairs, level crossings and the approach to light rapid transit

platforms: an 800 mm deep “corduroy” surface is required.

Products for curbramps and transit

platforms

The following materials are typically used for warnings at curb-ramps

and transit platforms.

• Pre-cast concrete pavers

• Natural stone

Other materials are currently being investigated.

Continued on next page
54 U.S. Access Board  Detectable Warnings: Synthesis

United Kingdom, continued

Products for other

applications

Typical products

• Rubber tile

• Vinyl

Occasionally used

for special purposes

• Hardwood

• Aluminum

• Stainless steel

• Brass nails

FIG. 4-4. BRASS NAILS INSTALLED IN

PAVEMENT AS DETECTABLE WARNINGS.

Durability In heavily trafficked areas, modules need occasional replacement to

maintain the detectable texture.

Slip Resistance There is no evidence that surfaces are slippery under any conditions.

Acceptance Acceptance of truncated dome detectable warnings (blister surfaces) is

good.

• They are reported to be helpful to people with visual impairments.

• Some people having mobility impairments report having

difficulties, therefore the extent of the surface is limited.

• No adverse impact has been reported for the general public.

Information

provided by

Sue Sharp, Disability Policy

 Branch, Mobility Unit

Dept. of the Environment,

Transport and the Regions

Floor 1/11, Great Minster House

76 Marsham St.

London SW1P 4DR, England

Phone: +44 (0) 171 890 4917

Fax: +44 (0) 171 890 6102

E-mail:

sue_sharp@detr.gsi.gov.uk

Peter Barker, Manager

Joint Mobility Unit

Royal National Institute

 for the Blind

224 Great Portland St.

London W1N 6AA, England

Phone: +44 (0) 171-387 2233

Fax: +44 (0) 171-388 3160

E-mail: Pbarker@rnib.org.uk
U.S. Access Board  Detectable Warnings: Synthesis 55

Australia

History of use

 

Truncated dome warning surfaces have been specified since 1988,

but not required under the Building Code of Australia until 1999

(AS 1428.4 Design for access and mobility—Tactile ground surface

indicators for the orientation of people with visual impairment ).

• Required at curb-ramps, medians, stairs, ramps, escalators, around

overhead obstacles under 2000 mm in height from the floor, and at

main entrances to buildings where there is no curb separating the

pedestrian from the vehicular way

• Also becoming common at bus and trolley stops, railway

platforms and wharves

Specifications:

two types

Type A

• Dome height—4 to 5 mm

• Dome base diameter—23 ± 1 mm

• Dome top diameter—11.5 ± 1 mm

• Dome spacing—60 ± 1 mm apart, measured on the diagonal,

with diagonal alignment

Type B—recommended for outdoor use

• Dome height—4 to 5 mm

• Dome base diameter—35 ± 1 mm

• Dome top diameter—25 ± 1 mm

• Dome spacing—50 ± 1 mm apart, with parallel alignment

Location Warning surface locations are specified in the Building Code of

Australia.

• At curb-ramps: placed 300 mm back from the curb line,

600 mm deep, and the width of the ramp

• At medians and islands: placed 300 mm back from the curb line,

600 mm deep, and the entire width of the curb-ramp or cutthrough

• At high use vehicular areas such as parking lots: placed

300 mm back from the driveway, 600 mm deep, and full width

of the pathway

• At transit platforms: placed 600 to 900 mm from platform edge,

600 mm deep

List continued on next page
56 U.S. Access Board  Detectable Warnings: Synthesis

Australia, continued

Location, continued • At bus stops: placed 300 mm back from the edge of the road, 600

mm deep and 1800 mm wide

• At tops and bottoms of stairways and escalators: one tread width

from riser, 300 ± 10 mm deep for enclosed stairways and

escalators, and 600 ± 10 mm deep for unenclosed stairways and

escalators

Products

FIG. 4-5. (LEFT)

AUSTRALIAN CURB RAMP

WITH DETECTABLE

WARNING.

FIG. 4.6. (RIGHT)

CURB RAMP LEADING TO

HANDICAPPED PARKING

SPACE, AUSTRALIA.

• Concrete—must be 60-70 MPa (8,700-10,000 psi) in strength to

maintain luminance contrast in wet weather and to produce strong,

durable domes.

• Vitrified porcelain

• Synthetic rubber/vinyl

• Polymer plastic—on trial

• Layers of reflective paint—on trial

 

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 57

Australia, continued

Durability • Concrete and vitrified porcelain are durable, but domes can be

damaged when snowplows are not set carefully.

• Synthetic rubber/vinyl is subject to damage.

• Methacrilate resin cracks and chips.

Acceptance • People with visual impairments find them helpful provided they

have some instruction in their use.

• Major organizations of and for people with mobility impairments

agree that rises of 5 mm can be negotiated without difficulty.

• Truncated domes are not used in “Aged Care Residential

Facilities” as they could be hazardous to residents who shuffle.

Also, residents become familiar with layout of their residences and

do not need warnings.

• The general public experiences no problems.

• When used to warn of overhead protrusions where there is no

barrier, they protect all pedestrians.

Information

provided by

Murray Mountain

Access Design Solutions

103 New Street

Brighton, Victoria

Australia 3186

Phone: +61 3 9593 3750

Fax: +61 3 9592 9071

Mobile: 0414 589 414

E-mail: mountain@

alphalink.com.au

FIG. 4-7. DETECTABLE WARNING SURFACE

ACROSS FULL WIDTH OF SIDEWALK AT AN

ALLEYWAY (HAZARDOUS VEHICULAR WAY) IN

AUSTRALIA.
58 U.S. Access Board  Detectable Warnings: Synthesis

New Zealand

History of use

 

Truncated dome warning surfaces and guidance surfaces have been in

use in New Zealand since 1990.

They have been required since 1993 under NZS/AS 1428.4 Design for

access and mobility—Tactile ground surface indicators for the

orientation of people with visual impairment .

Most local authorities are using warning surfaces at intersections.

Texture of

warning surface

Specified by NZS/AS 1428.4 and Land Transport Safety Authority

Standards RTS 14 (June 1997)

Type A

• Dome height—4 to 5 mm

• Dome base diameter—23 ± 1 mm

• Dome top diameter—11.5 ± 1 mm

• Dome spacing—60 ± 1 mm apart, measured on the diagonal, with

diagonal alignment

Type B—(preferred in New Zealand)

• Dome height—4 to 5 mm

• Dome base diameter—35 ± 1 mm

• Dome top diameter—25 ± 1 mm

• Dome spacing—50 ± 1 mm apart, with parallel alignment

Location Warning surfaces are required:

• At curb-ramps: placed 300 mm back from the curb line,

600 mm deep, and the width of the ramp

• At medians and islands: placed 300 mm back from the curb line,

600 mm deep, and the entire width of the curb-ramp or cutthrough

• At high use vehicular areas such as parking lots: placed 300 mm

back from the driveway, 600 mm deep, and 600 mm min. wide

Products • Precast concrete

• Synthetic rubber

• Cobble stone with truncated domes

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 59

New Zealand, continued

Maintenance and

durability

• Concrete is extremely durable and maintenance-free.

• There are some maintenance problems with synthetic rubber.

• There has been minimal experience with snow removal, but this

does not seem to be a problem.

• Surfaces are not slippery in wet or dry conditions.

Acceptance • Positive feedback from people with visual impairments has been

received for 10 years.

• People with mobility impairments have a strong preference for

Type B warnings.

• No complaints by general public have been received except when

tiles are not installed flush with the ground surface.

• General recognition of tactile tiles at crossing points has increased

awareness of general population, making these crossing points

safer.

• People with multiple disabilities consider them helpful.

• People who are elderly report that they are helpful.

FIG. 4-8. DIAGRAM

SHOWING REQUIREMENTS FOR GUIDANCE

SURFACE AND DETECTABLE WARNING ON

CURB-RAMPS IN NEW

ZEALAND.

Curb ramp

with

detectable

warning

Sidewalk

24

600

Guidance surface

Information

provided by

Michael Browne, Mobility Research Centre

P.O. Box 9518

Newmarket

Auckland, New Zealand

Phone: +64 520-4953

Fax: +64 524-4177
60 U.S. Access Board  Detectable Warnings: Synthesis

Italy

History of use

 

A tactile warning surface, “Loges,” exhibited in Düsseldorf,

Germany was introduced in Italy in 1997.

• Loges is now used in 20 cities.

• Locations include subway stations, railway stations

and post offices.

Texture of domes A handbook describes the texture characteristics (Orientation and

safety guide-strip: Designer’s handbook).

• Full domes 5 mm high having diagonal alignment are used as a

warning.

• Truncated domes 5 mm high having diagonal alignment are used

to signal a danger that can be safely overcome.

• Dome base diameter—22 mm

• Dome spacing—55 mm with parallel arrangement

Location Distance of warning surface from the indicated danger varies.

• Placed 300-400 mm back from a danger that can be crossed

• Placed 500-700 mm back from a danger which cannot be crossed

• Depth of warning—400 mm

Products Commonly used materials are:

• Concrete (exterior use)

• Rubber (interior use)

• Reconstructed stone (areas of artistic or historic significance)

• Stoneware

Maintenance,

durability and

slip resistance

Maintenance and durability are not considered to be a problem.

• Surfaces are as easy to maintain as other paving or flooring

surfaces.

• Surfaces are as durable as other paving or flooring surfaces.

• Surfaces do not become slippery.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 61

Italy, continued

Acceptance Warning surfaces are well accepted in Italy.

• Blind pedestrians find them very helpful.

• Blind pedestrians consider that warning surfaces promote a

positive image of pedestrians with visual impairments, as they

travel with greater independence and confidence.

• People having mobility impairments do not find them

troublesome.

Information

provided by

Antonio Quatraro, Counselor in the domain of

the integration of the visually impaired.

Via L. Fibonacci 9

50131 Firenze, Italy

Phone: +39 335 246246

Fax: +39 55 588103

E-mail: a.quatraro@fol.it
62 U.S. Access Board  Detectable Warnings: Synthesis

France

History of use Use of warning surfaces began in France in 1989, along rail transit

platforms.

• French standard, NF P 98-351,1989, Footways—Provision for

disabled persons—Warning for caution—Characteristic and testing

of pedotactile warning devices for the blind and partially sighted,

specifies textures, locations and placement of warning surfaces:

- Along railway platforms,

- At crosswalks with cut curbs,

- At raised crosswalks.

• Warning surfaces have been required since September 1999 on

curb-ramps and on sidewalks where they adjoin raised crosswalks.

Specified texture The texture of the domes is:

• Dome height—5 mm

• Dome base diameter—25 mm (domes not truncated)

• Dome spacing—75 mm on center, with diagonal alignment

The dome profile is specified by French standard NF P98-351.

Figure 4-9 shows the dimensions of the dome.

 

25

5

FIG. 4-9. DIMENSIONS OF FRENCH DOME

PROFILE (FULL DOME, NOT TRUNCATED)

Placement of

warning surfaces

Depth of the warning surface and placement in relation to the street or

platform edge are the same for different environments.

• Placed 900 mm back from platform edge or bottom of curb ramp,

extending the length of the platform, or width of the curb ramp

• 420 mm deep

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 63

France, continued

Materials Commonly used materials are:

• Rubber

• Concrete pavers

• Methacrilate resin

• Stainless steel tiles or

stainless steel nails

The photograph in Figure 4-10

shows a detectable warning

installation with steel nails

manufactured by ACCESSIville.

FIG. 4-10. FRENCH

DETECTABLE WARNING NAILS.

Durability Concrete pavers have performed best in France.

• Rubber is difficult to adhere.

• Methacrilate resin cracks and chips.

Acceptance Warning surfaces are well accepted in France because of the

involvement of persons with disabilities in their design.

• Surfaces were field tested and approved by persons with visual

impairments and persons with mobility impairments.

• On rail transit platforms, all passengers tend to wait further from

the platform edge, behind the warning.

Information

provided by

Maryvonne Dejeammes

CERTU

9 Rue Juliette Recamier

69456 Lyon 06

France

Tel: (33)(0) 4 72 74 5867

Fax: (33)(0) 4 72 74 5930

E-mail: mdejam@certu.fr
64 U.S. Access Board  Detectable Warnings: Synthesis

Germany

History of use

 

Tactile ground surface indicators have been used in Germany since

1984.

• Warning and guidance surfaces are now in use in

approximately 1000 (17%) of German railway stations, and

they are widely used in pedestrian areas in towns and cities.

• Efforts toward standardization began in 1989.

• A sinusoidal wavy texture, in various dimensions, is used for

guidance and warning.

Standard texture

Standards to be published in April 2000 as DIN 32984.

• Texture is comprised of parallel rounded grooves.

• Grooves—3 mm deep

• Spacing—10 to 20 mm on center

Location TGSIs are used at curb ramps,

medians, top and bottom of stair

runs, transit platforms, and bus

stops.

FIG. 4-11. WARNING &

GUIDANCE SURFACE AT

GERMAN BUS STOP.

 

Products The following products are used in Germany.

• Concrete tiles

• Ceramic tiles

• Hard rubber tiles

• Metal plates

 

Maintenance and

durability

• Surfaces are easily cleaned using cleaning machines.

• Surfaces are less slippery than normal concrete surfaces when wet,

oily or icy.

• Surfaces are adequately durable.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 65

Germany, continued

Acceptance

FIG. 4-12. GERMAN

TGSI PATH DOWN A

SIDEWALK AND TO A

CROSSWALK.

The guidance system is well accepted by all groups.

• Blind pedestrians who use a long cane find the guidance system

helpful, but travel somewhat more slowly using the system than

when not using it.

• Surfaces are well accepted by people with mobility impairments

because they comply with a standard requiring a minimum tremor

to wheels when crossing structured surfaces.

• Most rail passengers seem to use the guidance system as an

indication of the limit of the safe waiting area on the platform.

• Older persons comment that their feet don’t get cold when they 

stand on rubber guidance tiles at bus stops.

Information

provided by

Gerhard Kuper

Von-Siemensstr. 6A

D 22880 Wedel, Germany

Phone & Fax: +49 4103-87083

E-mail: Gerhard.Kuper@

arcormail.de

Volker Koenig

Wiedetwiete 42

D 22880 Wedel, Germany

Phone: +49 4103 84311

Fax: +49 4103 180438
66 U.S. Access Board  Detectable Warnings: Synthesis

Austria

History of use

 

Warning surfaces have been used in Austria since 1992, primarily on

transit platforms.

Approximately 80% of metro stations in Vienna have warning

surfaces.

Specifications for

warning textures

(“attention fields”)

ÖNORM V2102, adopted in 1997, specifies the dimensions of tactile

indicators for warning (attention) and guidance, and the dimensions

and placement for installations on transit platforms and on public

rights-of-way. Warnings can be either truncated domes or truncated

pyramids.

• Height—5 mm preferred;

4 mm minimum acceptable for exterior use;

3 mm minimum acceptable for interior use

• Dome diameter—base 30-40 mm; top 20-30 mm

• Dome spacing—50-70 mm on center

• Pyramid side—base 30 mm; top 20 mm

• Pyramid spacing—45-50 mm on center, with parallel alignment

• Warning and guidance indicators should contrast visually with

adjoining surfaces by at least 30%.

Placement and

dimensions

ÖNORM V2102 also specifies dimensions and placement of warning

textures to indicate changing situations and boarding locations on

transit platforms and public rights-of-way.

• At changing situations, warning indicators should be 300-400 mm

from a change such as a drop-off, stairs or a ramp; they should be

400-1000 mm deep.

• At boarding locations, warning indicators should be 100-120 cm

square.

• At cut-through islands or medians, a 600 mm deep warning

indicator should be placed at each side of the island.

• At raised crosswalks, warning indicators should be placed on the

sidewalk 300-400 mm from the curb line.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 67

Austria, continued

Materials Materials used for warning indicators are:

• Stone • Concrete • Road marking paint

Maintenance,

durability and slipresistance

Maintenance, durability and slip resistance of warning indicators are

not a problem.

• Stone and concrete surfaces have not deteriorated.

• Road marking paint is in good condition after seven years.

• Snow and ice removal is not considered a problem.

• Warning surfaces are sometimes slippery, but only when

surrounding surfaces are also slippery.

Acceptance Warning indicators are well accepted.

• Pedestrians with visual impairments find them very helpful.

• There have been no complaints from persons with mobility

impairments.

Information

provided by

Günther Ertl

Wiener Linien-Vproj

A-1030 Wein

Erdbergstrasse 202

Vienna, Austria

Phone: +43 (0) 1 7909-41300

Fax: +43 (0) 1 7909 41390

E-mail:

guenther.ertl@wienerlinien.co.at

FIG. 4-13. (LEFT) A

LINEAR DIRECTIONAL

SURFACE LEADS TO AND

BEYOND A LEVEL RAIL

CROSSING. A DETECTABLE WARNING SURFACE

EXTENDS FROM BUILDING TO CURB LINE ON

BOTH SIDES OF TRACKS,

VIENNA, AUSTRIA.

FIG. 4-14. (RIGHT)

A LINEAR DIRECTIONAL

SURFACE LEADS TO A

DETECTABLE WARNING

SURFACE AT A CURB,

VIENNA, AUSTRIA. 
68 U.S. Access Board  Detectable Warnings: Synthesis

Netherlands

History of use

 

In the early 1980s a rubber warning surface was introduced in

Holland.

• Although detectability seemed good, the surface was not

sufficiently durable.

• Extensive research has been conducted on 40 surfaces. .

Recommended

texture

A truncated dome (“blister”) surface is now recommended for

warning.

• 25 domes in 30 x 30 cm module

Location Warnings should be 60 cm deep, and as wide as the hazard. They

are recommended for use in the following types of locations:

• Dangerous crossings

• All crossing points where there is no level difference between the

pedestrian way and the vehicular way

• Tops and bottoms of stairs

• Bus stops

• “Decision points” where tactile guidance surfaces intersect

Products The product currently recommended is a metal plate that

has been pre-formed with

blisters, glued on 30 x 30 cm

concrete, then coated with a

gritty white or yellow epoxy

layer.

FIG. 4-15. DETECTABLE

WARNING PAVERS

AT A BLENDED CURB.

Information

provided by

Henk Grotendorst

Dutch Federation of the Blind and Partially Sighted

Postbus 2062

3500 GB Utrecht

Phone: +30 299 28 78

E-mail: h.grotendorst@sb-belang.nl
U.S. Access Board  Detectable Warnings: Synthesis 69

International standardization

International

Organization for

Standardization

(ISO)

ISO is a worldwide federation of national standards bodies.

• International Standards are prepared through the work of ISO

technical committees and working groups.

• International organisations, governmental and non-governmental,

in liaison with ISO, participate on technical committees and

working groups.

• Adoption of ISO standards by member countries is voluntary.

Technical

Committee 173

(ISO/TC173)

ISO/TC173-Technical systems and aids for disabled or

handicapped persons-

• Has a number of working groups, including one on tactile

ground/floor surface indicators (TGSIs).

• Working Group 7 completed Committee Draft ISO/CD

11550.2(E), Technical aids for blind and vision impaired persons

Tactile ground/floor surface indicators (TGSIs) in November

1999.

ISO draft on TGSIs • Specifies requirements for design and installation of tactile

indicators for use on ground or floor surfaces to assist the

orientation and mobility of people with visual impairments

• Includes specifications for warning, directional, and shared

pedestrian/cycle surface indicators

Warning surface

The warning surface is comprised of truncated domes:

• Dome height5 ± .5 mm

• Dome top diameter12-25 mm

• Dome spacing50-65 mm on

Directional surface

The directional surface is a series of raised elongated bars running in

the direction of pedestrian travel:

• Bar height5 ± .5 mm

• Bar top width30 ± .5 mm

• Bar spacing75 ± .5 mm on center

Continued on next page
70 U.S. Access Board  Detectable Warnings: Synthesis

International standardization, continued

ISO draft on TGSIs,

continued

Shared pedestrian/bicycle indicator

The shared pedestrian/bicycle indicator is:

• A central delineator strip: trapezoidal profile, 150 ± 1 mm wide

• Trapezoid height: 12-20 mm ± 1 mm

• Top surface: 50 ± .1 mm

Contrast luminance factor

Recommended minimum of 30% luminance contrast between tactile

indicators and surrounding surfaces

Applications Applications for warning surfaces are:

• Curb-ramps

• Crossings where there is a raised road surface

• Vehicle crossovers with high traffic flows

• Pedestrian refuges/medians

• Railway platforms and passenger wharves

• Level railway crossings

• Stairways and moving stairs

• Intersections with shared pedestrian/bicycle traffic

• Shared pedestrian/bicycle paths

Installation of

warning surfaces

Warning surfaces are to be:

• Installed across the full width of the trafficable surface

• Installed perpendicular to the path of travel

• Set back a maximum of 400 mm from the hazard

• Have a minimum depth of 400 mm (600 mm preferred)

• Have a base surface level 0-3 mm above the

surrounding surface

• Laid so there is no likelihood of surfaces lifting

• Have slip resistance in accordance with the standard of

the country where the application is laid
U.S. Access Board  Detectable Warnings: Synthesis 71

Chapter 5



U.S. Use of Detectable Warning

Surfaces: Case Studies

Summary This chapter includes information on use of truncated dome detectable

warnings in the U.S. The method of obtaining information is

described, and a summary of the information is given. The chapter

concludes with case studies of selected cities and rail transit systems

where truncated dome detectable warnings have been installed. Case

studies include history, locations, maintenance and durability, and

acceptance of detectable warnings in each location.

Chapter contents This chapter covers the following topics:

 Topic Page

 Locating U.S. installations of detectable warning 

surfaces 72

 Responses to mail survey 73

 Interviews regarding detectable warning installations 74

 Interview locations 75

 Interview questions 76

Interview results  general; installation problems;

Maintenance; durability; public reaction 77

 Austin, TX 82

 Metropolitan Atlanta Rapid Transit Authority 

(MARTA), Atlanta, GA 84

 Roseville, CA 86

 Metro North Railroad, greater New York City 88

 Harrisburg, PA 90

 Massachusetts Bay Transportation Authority 

(MBTA), Boston, MA 92

 Cleveland, OH 94

 Baltimore County, MD 96

 Bay Area Rapid Transit (BART), San Francisco, CA 98

Claremont, CA 100
72 U.S. Access Board  Detectable Warnings: Synthesis

Locating U.S. installations of detectable warning surfaces

Developing a

list of locations

An E-mail survey was sent to several mailing lists of individuals who

might have information regarding locations of detectable warnings

surfaces in the United States. Manufacturers were also contacted and

installation locations were requested. Available pedestrian design

guidelines were also reviewed to determine locations that currently

require a truncated dome detectable warning surface.

Mail survey In October 1999, a survey was sent to E-mail listserves whose

subscribers might be aware of locations where a texture change is used

to provide information to pedestrians who are visually impaired or

blind.

• Groups included pedestrian advocates, orientation and mobility

specialists, Association for Education and Rehabilitation of the

Blind and Visually Impaired (AER), individuals who are blind or

visually impaired, and traffic engineers.

• Survey requested specific locations, types of location (curb ramp,

transit platform, edge of street, medians) and the texture (grooves,

grid pattern, brick, rubber mat, truncated domes, or other), of any

texture change intended to provide information to pedestrians with

visual impairments.

• Survey requested the name of a contact person who might be able

to answer questions about experience with truncated dome

detectable warning surfaces.

Other information

sources

Additional information was gathered about installations from:

• Manufacturers of truncated dome detectable warning materials

were asked for contacts in locations where their products had been

installed

• Conversations with Access Board staff

• A review of references in previously published materials

• Personal contacts of authors

• American Public Transit Association
U.S. Access Board  Detectable Warnings: Synthesis 73

Responses to mail survey

Responses to

survey

The 48 responses included surveys from 28 states, the District of

Columbia and Canada

• Many respondents noted two or more locations and types of

locations, for example, the name of an entire transit system that

had detectable warnings and a list of several intersections in that

city with grooves on the curb-ramps.

• Five respondents replied that they were not aware of any locations

where a texture change was used.

• Thirty-nine reported the use of other surfaces besides, or in

addition to, truncated domes, including grooves, grid patterns,

standard bricks, exposed aggregate, and “exposed rock.”

State and local

requirements

FIG. 5-1.

A MINIMALLY DETECTABLE WARNING SURFACE

IN PORTLAND, ME.

Responses from several states indicated that there were state or local

requirements for tactile surfaces on curb-ramps.

• For example, a traffic engineer from Minnesota stated that an

exposed aggregate was required on all curb-ramps,

• and a response from Phoenix stated that grooves were required on

curb-ramps in all new construction.

• California requires grooves at the top of the curb ramp and

detectable warnings where the slope is less than 1:15.
74 U.S. Access Board  Detectable Warnings: Synthesis

Interviews regarding detectable warning installations

Interview Research assistants made calls to locations identified by the initial

survey as having truncated dome detectable warnings.

The detectable warning and its location was confirmed and it was

determined that the individual being interviewed had some

responsibility related to its installation or use. Names of additional

contacts were requested.

Locating

appropriate

persons

Architects and facilities maintenance supervisors of transit systems,

ADA coordinators of transit systems and cities, traffic engineers, city

engineers, and various public works officials were queried.

• Phone calls were made to city public works departments,

engineering departments, and transit systems in order to locate

knowledgeable individuals.

• Some cities have a designated curb ramp managermany do not.

In several situations, the public official was unaware of the presence of

detectable warning within his/her jurisdiction until the researcher

identified the specific location.

Types of locations

for detectable

warnings

The people interviewed reported the following types of locations for

detectable warnings:

• Curb-ramps at intersections18 jurisdictions

• Curb-ramps throughout the city2 cities

• Entrances to public stores, between parking lot and entrance

4 jurisdictions

• Transit system platforms, or light rail loading areas, usually at

numerous locations throughout systems17 systems

• Raised intersection crosswalks, along driveways at a school for the

blind, and a university3 reports

FIG. 5-2. CURB RAMP

EXPOSED AGGREGATE

SURFACE IN VIRGINIA.

PEDESTRIANS WHO

ARE BLIND DO NOT

RELIABLY DETECT

EXPOSED AGGREGATE

CONCRETE.
U.S. Access Board  Detectable Warnings: Synthesis 75

Interview locations

City interviews Interviews were conducted for these cities:

• Roseville, CA

• Sacramento, CA

• San Diego, CA

• San Francisco, CA

• Lakeland, FL

• Chicago, IL

• Cambridge, MA

• Towson, MD

• Anoka, MN

• Greensboro, NC

• Portsmouth, NH

• Cleveland, OH

• Harrisburg, PA

• Austin, TX

Transit system Interviews were conducted for these transit systems:

Interviews • San Diego Trolley,

San Diego, CA

• Bay Area Rapid Transit,

(BART), San Francisco, CA

• San Francisco Municipal Railway (MUNI), San Francisco,

CA

• Valley Transportation

Authority, San Jose, CA

• AC Transit, San Pablo, CA

• Metrolink, Southern

California Commuter Rail

• Sacramento Regional Transit,

Sacramento, CA

• Metro-Dade Transit, Miami,

FL

• Metropolitan Atlanta Rapid

Transit Authority (MARTA),

Atlanta, GA

• Chicago Transit Authority,

Chicago, IL

• MTA and Maryland Area Rail

Commuter (MARC),

Baltimore, MD

• Massachusetts Bay Transportation Authority, Boston, MA

• Metro North Railroad,

Greater New York City, NY

• Cleveland Regional Transit

Authority, Cleveland, OH

• Portland TriMet, Portland, OR

• Virginia Railway Express,

Washington DC & VA

Other interviews Interviews were conducted with these individuals and organizations:

• Maintenance supervisor

at University of Alaska,

Fairbanks, AK

• Maintenance supervisor

at ARCO, Anchorage, AK

• Blind person in Canada

• Manager at a TOYS R US

store, Roseville, CA

• Manager of Checkers

Drive-In, Lakeland, FL

• Contractor in Atlanta, GA,

• Blind person in Towson, MD

• Consultant in accessibility

issues, Ottawa, ON, Canada

• Employee of Q-Lube,

Bonney Lake, WA

• Maintenance supervisor at the

Washington State School for

the Blind, Seattle, WA

• Contractor in Ontario, CA
76 U.S. Access Board  Detectable Warnings: Synthesis

Interview questions

Interview

questions

Interview questions were divided into five major categories:

• Location and materialsinformation about the exact location, type

of installation, and type of material including the manufacturer, if

known

• Installationdate installed, approximate cost per square foot,

installation method, color of detectable warning and problems or

difficulties in the installation process

• Maintenance and durabilitymaintenance problems, cleaning

method and products, evidence of wear and tear and extent of the

problem, experience with snow and ice removal, and whether any

replacements have been needed

• Public Reaction/Problems/Concernsspecific instances where

truncated domes have been the cause of pedestrian complaint, or

legal action; comments from individuals who are blind, who have

mobility impairments, or from the general public

• Additional Information/ContactsContacts were asked for names

of other knowledgeable individuals, photos of the detectable

warning installations, any research on detectable warnings, and

about their plans to install more detectable warnings.

See the Appendix for a copy of the interview questionnaire and

specific questions asked in each area.

Snow removal

FIG. 5-3. (LEFT)

CURB RAMP IN

ANCHORAGE, AK.

FIG. 5-4. (RIGHT)

CURB RAMP IN

ANCHORAGE, AK

SHOWING SNOW

REMOVAL WITH A

BRUSH. 

A
U.S. Access Board  Detectable Warnings: Synthesis 77

Interview results  general

Materials A wide range of materials were reported:

• Unit masonry

• Precast concrete units

• Concrete, stamped after pour

• Epoxy polymer composite tile

• Ceramic tile

• Plastic/rubber urethane tile

• Latex-modified mortar

Some of the originally installed products are no longer commercially

available and some of the manufacturers are no longer in business.

See Chapter 7, U.S. Detectable Warning Manufacturers.

At several locations the original material was unsatisfactory, but

replacement detectable warnings from the same or a different

manufacturer have been installed and are functioning in a satisfactory

manner.

Color of

detectable warning

Colors used included safety yellow, light gray, red brick, black and

blue.

Installation dates Dates of installation ranged from 1986 to 1999.

Installation costs Although cost per square foot information was requested in each

interview, it was generally unavailable, or impossible to adequately

compare with other installations due to the variations in materials,

installation methods (whether installed by manufacturer or a

contractor), job size, and dates of installations. Therefore, responses

are not reported here.

Installation method Most panel or sheet type materials were mechanically fastened, as well

as glued to the surface material. Some types of panels are specifically

manufactured with a flange to be set in wet concrete.

Brick and paver type materials are installed using standard procedures.

Stamped concrete requires precise attention to dome height,

appropriate pressure in the process, and curing of the concrete.

Detailed specifications and contractor requirements for installation

methods and materials have been developed by Roseville, CA; Austin,

TX; Cambridge, MA; Towson, MD; and many of the transit systems

queried.
78 U.S. Access Board  Detectable Warnings: Synthesis

Interview results  installation problems

Installation

problems or

difficulties

Many installation

difficulties were

considered minor by

the individuals

reporting them

There were a number

of negative reports

about stamping in

concrete.

Various types of difficulties were reported, many of which were

considered minor by the individual reporting them. Each type of

material requires a specified procedure.

Transit systems using tiles generally had to grind down a section of the

platform edge to retrofit their systems with the detectable warning.

Two specifically reported that it was a much easier process than

anticipated, since the manufacturer had equipment that handled the

requirements.

A number of negative reports involved the process of stamping the

truncated dome surface in concrete, with very few successful

experiences. Stamping the dome texture on sloping concrete and

getting an acceptable consistency of surface, dome height, and concrete

hardness seemed to be an extremely difficult process, requiring expert

contractors. One public works official in Minnesota stated that the

dome surface had worn better than he expected, but he would not

install it again as stamped concrete because the process was too

difficult.

Contractors were generally reported to be familiar with the methods of

setting brick pavers, even on a sloped surface. Setting pavers in mortar

was suggested by the experience in several locations.

The problems reported with pavers were related to cutting the pavers to

fit curves, and the lack of guidelines for maintaining the distance

between domes when materials needed to be cut to fit a curve, such as

at the base of a blended curb ramp.

Precast truncated dome units for curb-ramps are manufactured in

specific sizes, requiring consistency in the curb ramp type and

placement.
U.S. Access Board  Detectable Warnings: Synthesis 79

Interview results  maintenance

General

maintenance

Cleaning method and products were standard. Most curb ramp

installations were not cleaned. Many indoor transit locations were

pressure washed. One location reported using solvents, as necessary.

Frequency of cleaning ranged from “never” to weekly.

Snow & ice

removal

Experience, method and comments regarding snow and ice removal

were requested. Concerns about snow and ice removal have been one

of the barriers to installation of truncated dome surfaces, so questions

were specifically asked regarding experience with clearing snow and

ice.

Number of cities Experience with

or transit systems snow & ice removal

22 No experience with snow or ice

3 Recent installation and no experience to date

16 Have had experience with snow and ice

Various methods of clearing, including snowplows, brushes or brooms,

and chemicals, were reported.

While concerns continue to be expressed about damage to the domes

from snowplows, only three people stated that plows removed domes.

One said that snowplows removed domes at apex curb-ramps while

another stated that it was “no problem because the domes are set in

concrete and the blade passes over them”. The same person also stated

that truncated domes were “preferred to grooves because they

(truncated domes) don’t fill up with snow and dirt.” Clearly, there has

been a variety of experience, depending on the equipment and the

detectable warning material.

• A report from Anoka, MN stated: “People thought shovels would

shear off domes, but they don’t. Brooms work much better ...

either do that or flood with salt. Plows break some domes off.”

• One commented: “Use brooms and sand. Any water will collect

below the domes while people step on top.”

• A plow with a rotary brush was recommended.

• Two people reported problems with salt degrading the domes on

stamped concrete surfaces and another commented “no problems,

chemicals don’t seem to hurt.”

• Chemicals may make some types of detectable warning materials

slippery.
80 U.S. Access Board  Detectable Warnings: Synthesis

Interview results  durability

Durability

“We do not take any

special precautions

during snow removal

and it seems to have

held up quite well.”

“Yes, it is plowed

mainly with a front end

loader with a bucket.

It scrapes the ground

pretty hard so [the

detectable warning]

takes quite a bit of

abuse.”

Ed Foster, Univ. of

Alaska Fairbanks

Maintenance.

Specific questions were asked about problems with tiles chipping, color

fading, domes wearing, tiles peeling, and whether these of problems

were considered minor, major or no problem

• More than one transit system facility supervisor stated that although

tiles had to be replaced regularly, they considered that a typical

maintenance item and did not see it as a problem.

• Numerous problems with peeling and bubbling were reported in

early installations of rubber tiles, particularly in outdoor

installations. Many of those installations in transit systems have

been replaced with a different material. Adhesives alone may not

be adequate in outdoor installations and care must be taken to

follow manufacturer’s recommendations.

• A detectable warning, thought to be Pathfinder Tile, was installed

before 1996 in Fairbanks, AK, and it is still in good condition. It is

across a driveway and subject to extreme cold, regular plowing, and

some traffic by heavy vehicles. On a similar detectable warning

installed in Anchorage, Alaska, snow is regularly removed with the

same brush used for sidewalk snow removal (see Fig. 5-4).

FIG. 5-5. DETECTABLE

WARNING SURFACE

WITH A PARTIAL SNOW

COVER BETWEEN THE

DOMES, ANCHORAGE,

ALASKA.

• Seven of the transit systems

and two cities noted color

fading. Three indicated that it

was major, with two saying

that the manufacturer either

replaced or re-coated the

materials. All others reported

the fading as minor.

• Problems with wear on domes

were generally reported by

cities with curb ramp locations

where a “stamped after pour”

concrete surface was installed.
U.S. Access Board  Detectable Warnings: Synthesis 81

Interview results  public reaction

Public reaction,

problems or

concerns

Pedestrians who are

mobility impaired find

the truncated domes

just “more difficult to

manage.” A city ADA

coordinator

Public reaction seems to have been most positive in locations where

the disability community was involved in the Americans with

Disabilities Act (ADA) transition plan and making decisions regarding

the use of detectable warnings.

One question asked about specific instances where truncated domes

have been the cause of pedestrian complaints or problems. Five

locations answered that there was an instance of pedestrian complaint.

One was a mobility impaired individual using a cane, who found the

truncated domes more difficult to traverse. A city ADA coordinator

stated that pedestrians who are mobility impaired find the truncated

domes “just more difficult to manage”. Another stated that there were

complaints from women in high heels, but no injuries.

There were two instances in which legal action was reported in

association with a truncated dome detectable warning. The authors of

this report made extensive phone calls to attempt to document the

details, as noted below.

No record

of any lawsuits

“I think this is one of

those urban myths.”

A city risk manager.

In one case, the Manager of Construction and Maintenance for a city

stated that truncated domes were no longer installed on curb-ramps in

that city because there were “too many lawsuits from women in high

heels.” However, he said he knew no details and referred us to the

Engineering Manager. Phone conversations with the managers and

staff of the engineering and traffic operations departments failed to

locate any information.

The city’s department of Risk Management was contacted and stated

that there was no record of any lawsuits associated with curb-ramps or

truncated dome detectable warnings in the past seven yearsthe

detectable warnings were installed six years ago. The Risk

Management department Manager stated “I think this is one of those

urban myths.”

Lawsuits,

but no details

In another situation, the transit system construction manager stated that

there had been two lawsuits. He did not know any details and said his

only knowledge was that the city had contacted him with general

questions regarding the installation of the detectable warning material.

Further information could not be located.
82 U.S. Access Board  Detectable Warnings: Synthesis

Austin, Texas

History The city of Austin has installed truncated dome detectable warnings at

curb-ramps since 1992.

• The disabled community was involved in preparing an ADA

compliance transition plan.

• When Austin began putting in curb-ramps, detectable warnings

were required. Even though the federal detectable warning

requirement was subsequently suspended, the state of Texas

continued to require the use of either truncated dome detectable

warnings or grooved surfaces at curb-ramps.

• A recent rules change now permits the use of grooved surfaces in

residential or industrial areas; however, truncated dome detectable

warnings are required within the Central Business District and in

the area surrounding the school for the blind.

• Additionally, truncated dome detectable warnings are required

at any curb ramp that is constructed using public funds.

Over 1000 ramps in Austin now have truncated dome detectable

warnings.

Materials and

Installation

• In 1992, the first installations were stamped concrete approximately 4 ft x 6 ft, covering the entire ramped area.

• This practice was discontinued due to the difficulty associated

with stamping the concrete and the poor durability of the painted

surface.

• Dark red brick pavers have been installed since 1995.

• Pavers are installed in the full width and depth of the ramp,

exclusive of the flares, typically an area of 4 ft x 5 ft.

• There were problems with settling when pavers were installed

in sand, but setting in mortar solved that problem.

Specifications

FIG. 5-6. MID-BLOCK

CROSSING WITH CURB

RAMP, AUSTIN.

City of Austin standard

specifications and standard details

are available on the internet at

www.ci.austin.tx.us. From the

pull down menu, select Quick

Connections >Development

Process > Standard Details &

Specifications.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 83

Austin, Texas, continued

Maintenance and

Durability

Ken Zimmerman, Project Managerwith the ADA Curb Ramp and

Sidewalk Program reports no problems with wear, except possibly

some fading.

• Pavers are never

washed.

• There has been no

experience with snow

or ice.

• Revising the

installation method

solved the problem of

settling.

• A few individual

pavers have been

replaced due to

settling and damage

from trucks.

FIG. 5-7. DETECTABLE WARNING

BRICK PAVERS, AUSTIN, TEXAS.

Acceptance

The general public is

supportive.

• Ken Zimmerman said he thinks wheelchair users would “prefer no

bumps”, but there have been no complaints.

• General public is “supportive”.

• Originally detectable warnings were installed across sidewalks at

commercial driveways having blended curbs or curb-ramps.

Comments from blind individuals led to discontinuing installation

of detectable warnings at commercial driveways because blind

pedestrians sometimes counted them as streets and thus became

disoriented.

• Representatives of the Commission for the Blind, the Texas

School for the Blind, and Council of the Blind have attended

meetings and hearings and have expressed support for the curb

ramp program

Contacts Dolores Gonzalez

ADA Coordinator

City of Austin

PO Box 1088

Austin, TX 78767-8839

Phone: (512) 499-3256

E-mail:

Dolores.Gonzalez@ci.austin.tx.us

Ken Zimmerman,

Project Manager, ADA Curb

Ramp and Sidewalk Program

Dept. of Public Works & Transportation, City of Austin PO Box

1088, Austin, TX 78767-8839

Phone: (512) 499-7138

E-mail:

ken.zimmerman@ci.austin.tx.us
84 U.S. Access Board  Detectable Warnings: Synthesis

Metropolitan Atlanta Rapid Transit Authority (MARTA)

History

 

MARTA, the Metropolitan Atlanta Rapid Transit Authority, in Atlanta

Georgia, as part of their ADA compliance plan, agreed to install

truncated dome detectable warnings at all platform edges in all stations

in the system.

• Working with the Elderly and Disabled Access Advisory

Committee, MARTA staff evaluated detectable warning materials

& installation methods, & determined an installation priority list.

• Installation of detectable warning began in 12 stations in 1992.

All 36 stations now have truncated dome detectable warning

along the edge of the platform.

• Detectable warnings will be installed in all new stations as

required by ADAAG.

Materials At this time, the detectable warnings are either Armor-Tile or HighQuality Tile. All are a hard surface, rather than resilient material.

MARTA has a very exacting performance specification and other

manufacturers have not been able to meet all their requirements.

In the most recent installations, MARTA has been using a precast

Armor-Tile concrete panel that has the warning tile placed on it at the

factory. This tile is installed on the concrete slab and “aligns better”.

Installation Detectable warning is installed 2 ft deep for the length of the platform,

with a space underneath to enhance sound on cane-contact difference.

• Tiles are secured with mechanical fasteners and structural adhesive.

• In the retrofit installations, the detectable warning tiles replaced a

two-foot portion of a three-foot granite strip along the edge of the

platform, which was originally installed as a tactile warning. A

portion of the granite strip was ground down to allow installation of

the tiles. This installation was accomplished in stages, with most of

the construction done at night when trains were not in service.

• Tiles are a gray color, preferred by MARTA architects to provide

contrast with the original platform colors.

Maintenance The detectable warning is pressure washed and scrubbed approximately

bimonthly. MARTA has had very little experience with snow and ice

removal. Barry Hodges, MARTA’s Manager of Architecture states

that there is not a problem, because the engineering and design of the

tile prevents water from pooling or icing on the tile.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 85

Metropolitan Atlanta Rapid Transit Authority, continued

Durability • Problems with chipping, cracking and occasional lost screw covers

were reported as minor by MARTA staff.

• The chipping of the detectable warning surface at the platform edge

has been determined to be caused by either MARTA’s money carts,

or escalator equipment carts, which are very heavy and moved from

station to station via rail. Replacing the carts’ steel wheels with

rubber wheels has largely solved this problem. The previous

granite edge strip had been cracked and required repair for the same

reason, so the chipping of the Armor-Tile is not considered

significant.

Acceptance No complaints have been documented.

• The detectable warning installations have been very well received

by the patrons. Several blind or visually impaired individuals have

expressed appreciation in public hearings regarding the addition of

the detectable warnings.

• MARTA staff has stated that the detectable warnings encourage all

patrons to stand back from the edge of the platform.

Contact

FIG. 5-8. MARTA

STATION SHOWING

INSTALLATION OF

ARMOR-TILE.

Barry Hodges, Manager of Architecture

MARTA, 2424 Piedmont Road, Atlanta, GA 30324

Phone: (404) 848-4434

Fax: (404) 848-4329
86 U.S. Access Board  Detectable Warnings: Synthesis

Roseville, California

History California Title 24 regulations require detectable warnings on curbramps that slope less than 1:15 (6.67%). Grooves are required around

the top edge of the curb ramp and a 1⁄2 in beveled lip is required at the

curb line.

• The City of Roseville requires that curb-ramps have a maximum

5% slope when street slopes allow this.

• All curb-ramps, regardless of slope and design shall include

detectable warnings.

• As curb-ramps are added, detectable warnings are included.

• Detectable warnings are installed at all driveways that include curb

radii, such as high volume commercial driveways.

• Detectable warnings are installed at the access and egress points of

corner islands.

Currently “several hundred” curb-ramps have detectable warnings.

Materials and

installation

FIGURE 5-9. CURB

RAMP DESIGN

REQUIRED IN

ROSEVILLE,

CALIFORNIA.

• Since August 1997, Roseville’s specifications require a specially

manufactured Armor-Tile panel, 3 ft deep x 4 ft wide, installed at

the back of the curb.

• This panel is manufactured in safety yellow, with parallel

alignment of the rows of truncated domes.

• There is a 11⁄2 in flange around the detectable warning surface,

which is set into wet concrete when the ramp is poured.

• Specifications are available from Rick McCarter (contact

information below).

detectable warning

Flared side Curb ramp with

Grooved border

Sidewalk

36915

1/2" beveled

lip

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 87

Roseville, California, continued

Maintenance • Tiles are not cleaned on a regular basis; rain washes them off

• There has been no experience with snow or ice.

Durability • No problems with cracking or lifting of panels have been observed,

since it is installed in the concrete

• The color has faded somewhat.

Acceptance There has been good agreement from local disability groups in

deciding appropriate placement and solutions. They worked together

on requirements and on how to resolve differences.

• Parallel alignment of domes on detectable warning material is

helpful to wheelchair users.

• No complaints have been received.

Contact

FIG. 5-10. PARALLEL

CURB RAMP IN

ROSEVILLE USING

ARMOR-TILE PANEL.

Rick McCarter, Senior Public Works Inspector

City of Roseville

316 Vernon Street #106, Roseville, CA 95678

Phone: (916) 774-5481

E-mail: rmccarter@roseville.ca.us
88 U.S. Access Board  Detectable Warnings: Synthesis

Metro North Railroad

History Metro North is the second largest commuter railroad in the nation.

Metro North's main lines are the Hudson, Harlem, and New Haven runs

northward out of Grand Central Terminal into suburban New York and

Connecticut. West of the Hudson river, Metro-North's Port Jervis and

Pascack Valley lines operate from NJ Transit's Hoboken Terminal.

Metro North operates 117 stations.

Metro North Railroad has installed detectable warnings along platform

edges in 29 stations, including indoor and outdoor, elevated and nonelevated stations.

• Installations took place from 1995 to 1997.

• Other agencies, vendors, and other systems were contacted in

determining appropriate materials and plans for ADA compliance.

Materials and

Installation

Detectable warnings are Lanxide (SMC) and Armor-Tile (Engineered

Plastics). Most are yellow. Detectable warnings are two feet deep

along the length of the platform, set back 4 inches from the platform

edge. Setback is to prevent damage from trains to the detectable

warning along the platform edge.

• Various installation methods have been tried, including riveting,

combining rivets and adhesives/mastics, and setting into wet

concrete with overlay type materials. All have some problems and

are less than satisfactory.

• Upcoming installation will probably be cast in place as that has

been most successful to date. Mr. Ziegler is working on developing

the best possible plans, but notes that there are difficulties anytime

a cold joint of two dissimilar materials is installed on the platforms

and exposed to the elements, particularly in elevated platform

situations.

• Some tiles were installed with a cavity between the detectable

warning and the base surface for sound difference, but this opens

up the concrete base to more possibilities of deterioration. The

setback from the platform edge also leaves a joint for water

intrusion creating freeze/thaw problems

• Setting in wet concrete was the most successful method of

installation in retrofit; however, concrete can puddle and it has to

be installed expertly.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 89

Metro North Railroad, continued

Maintenance • Detectable warnings are pressure washed on no set schedule.

• Snow plows and chemical are used to remove snow. Some

chipping has resulted from snow plow use. Calcium chloride

makes the surface of the detectable warning slippery.

• Domes are difficult to clean.

Durability Extensive concerns with durability were expressed.

• Cracks in both types of tiles are reported as a major problem. Mr.

Ziegler believes it is from freeze/thaw, snow removal, and car

washing equipment.

• The installation procedures for retrofitting tiles required milling up

the concrete of the platform, then installing the tiles. No matter

how well sealed, this exposed the concrete base to salt and water,

which caused it to deteriorate.

• More problems were reported with the SMC material and

ultraviolet, however there is fading in all products.

• In some instances the riveted overlay material was removed and

replaced with tiles set in concrete. This was due to platform

deterioration problems.

Acceptance Mr. Ziegler does not strongly favor detectable warnings, feels the “idea

was not well thought out” and is concerned by problems he’s had.

• He does not remember any favorable comments about the

detectable warning and has observed some slip resistance problems.

• He stated that there is a tripping hazard, particularly for “drunks

who run and trip on the detectable warning”.

Contact Kurt Ziegler

Metro North Railroad

420 Lexington Avenue, 11th Floor

Graybar, Engineering and Design Division

New York, NY 10017

Phone: (212) 499-4417

Fax: (212) 499-4420

E-mail: ziegler@mnr.org
90 U.S. Access Board  Detectable Warnings: Synthesis

Harrisburg, Pennsylvania

History

 

Detectable warnings were installed on 300 to 400 curb-ramps in the

downtown area of Harrisburg, PA in 1993-1994.

The truncated dome detectable warning surface covers the entire

ramped area, exclusive of the flares.

Shortly after project was begun, the requirement for truncated dome

detectable warnings was suspended. The experience and results,

according to City Engineer Joseph Link, was “less than what was

expected”.

Materials and

Installation

Units were precast, then installed in the ramp area with concrete poured

around them. Most units were brick red, for contrast with surrounding

concrete.

A local contractor was used for installation. When he attempted to

form the domes by the typical method of pressing the rubber mold into

the concrete, the “form stuck to domes and they pulled off”. The

contractor developed a process that worked, pouring the concrete into

the mold, then installing it in the ramp as a precast unit.

Maintenance Detectable warnings are not cleaned, except for normal rain washing of

the sidewalk.

Snow and ice are removed with salt, which may have degraded the

domes. The City Engineer stated that other methods of clearing don’t

work with the domes.

Durability

Major wear to the

concrete domes is

reported. Joseph

Link, City Engineer

• Although concrete was rated at 6000 PSI, domes broke off.

• Major wear is reported. Some settling is also reported.

• Individual units were replaced in a few instances where cracking

occurred. Cracking was thought to be caused by garbage trucks

driving over the units.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 91

Harrisburg, Pennsylvania, continued

FIG. 5-11. BRICK

DETECTABLE WARNING

SURFACE CONTRASTS

WITH ADJACENT

CONCRETE,

HARRISBURG, PA.

Acceptance No comments were received from individuals who are blind.

Mr. Link stated that most ramps are 1:12 and there are audible signals

at the intersections, so individuals who are blind do not have difficulty

recognizing the street.

An individual with a mobility impairment, who uses a cane and

cannot lift her feet well, complained. Another individual stated that the

bumpiness was bad for those wheelchair users with bladder problems.

Comments from the general public were: “What are those stupid

things for?”

Mr. Link was not pleased with the results. He states that he would

never do truncated domes again, that the color difference didn’t look

good and was not important, and that most of the domes are gone

anyway. He does not intend to install additional detectable warnings

unless mandated.

Contact Joseph Link, City Engineer

City of Harrisburg

123 Walnut Street, Suite 212

Harrisburg, PA 17101

Phone: (717) 255-3091

Fax: (717) 255-3078

E-mail: jlink@cityofhbg.com
92 U.S. Access Board  Detectable Warnings: Synthesis

Massachusetts Bay Transportation Authority (MBTA)

History

 

Detectable warnings have been installed at approximately sixty-one

stations in the Massachusetts Bay Transportation Authority (MBTA)

system, including rapid rail, light rail and commuter rail stations,

indoors and outdoors.

• Most have been installed since 1993.

• Research on detectable warnings was done before, during and after

the installation of the detectable warning.

• A number of different products have been installed in the system.

Materials and

Installation

Materials vary since the type of detectable warning and manufacturer

are subject to the competitive bidding process.

• Installations include detectable warnings of epoxy, plastic and

ceramic tiles. The detectable warning materials are adhered with

adhesives, fasteners and/or screws directly on the base surface.

• All detectable warnings are yellow, in accord with the

specifications of the Massachusetts Architectural Access Board.

• The detectable warnings in all stations are 24 in deep by the length

of the platform, installed at the edge of the platform.

Maintenance No maintenance issues

were reported.

• Detectable warnings

are washed on a “nonregular basis”, using a

hose and water.

• Snow and ice are

removed by shovel,

sand and broom.

FIG. 5-12. MBTA STATION

WITH DETECTABLE WARNING TILE (SUMMITVILLE).

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 93

Massachusetts Bay Transportation Authority, continued

Durability • Some tiles are missing, peeled, cracked and chipped and the surface

texture of a few detectable warning tiles has degraded somewhat.

• Detectable warning products have been removed and reinstalled at

several stations.

• The color of a few tiles has degraded with some discoloration.

• A few tiles have been replaced.

Acceptance No comments or complaints have been received regarding the

detectable warnings.

Detectable warnings will be installed throughout the system.

Contact Michael Festa, Senior Accessibility Specialist for Design

MBTA Design and Construction Department

500 Arborway, Jamaica Plain, MA 02130

phone: (617) 222-1984 TTY

fax: (617) 222-3426

E-mail: mfesta@mbta.com
94 U.S. Access Board  Detectable Warnings: Synthesis

Cleveland, Ohio

History

 

Detectable warnings were installed on curb-ramps on the Public Square

in the city of Cleveland in 1996.

Materials and

Installation

Brick pavers are “the

only thing that works

in northern climates.”

Detectable warnings are brick units, 4 in x 8 in x 3.5 in, in a red brick

color. Full depth bricks are used rather than face bricks for durability.

• The manufacturer’s name is not available. The contractor selects

the manufacturer.

• Units were installed in sand with a 4 in concrete base underneath on

the entire ramped area, approximately 5 ft x 6 ft.

Randy DeVaul, Commissioner of Engineering, stated that truncated

domes are more costly and he prefers ridges that can be sawed.

Mr. McLaughlin stated that brick pavers are the “only thing that works

in Northern climates,” and that stamped surfaces of the truncated dome

texture were impractical.

Maintenance No maintenance problems were reported.

• Detectable warnings are swept or hosed down on “no set schedule”.

• Snow and ice are removed by snow plow, shovel, or salt. Mr.

DeVaul expressed concerns about snow removal and snow building

up and becoming slippery.

Durability No problems were reported with durability.

A few bricks have broken or become loose from trucks driving over

them, but “anything else would be broken up by that.”

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 95

Cleveland, Ohio, continued

Acceptance No problems have been reported.

Contacts Bill McLaughlin

Consulting Engineer, Division

of Engineering & Construction

City of Cleveland

601 Lakeside Ave.

Cleveland, OH 44114

Phone: (216) 664-4278

Fax: (216) 664-2289

Randy DeVaul

Commissioner of

Engineering & Construction

City of Cleveland

601 Lakeside Ave.

Cleveland, OH 44114

Phone: (216) 664-2371

FIG. 5-13. TRUNCATED

DOME PAVERS CUT AND

FITTED TO THE ENTIRE

SURFACE OF A PERPENDICULAR CURB RAMP,

INCLUDING FLARES,

CLEVELAND, OH.
96 U.S. Access Board  Detectable Warnings: Synthesis

Baltimore County, Maryland

History Detectable warnings are used in numerous curb ramp locations in

Baltimore County, MD. They have been installed mainly where older

commercial areas are being “revitalized”.

At one location a band of detectable warning materials was placed

around the perimeter of the ramp, as well as 32” at the base of the

ramp. Now, a 32 in deep section of detectable warning material is

installed at the base of the ramp.

Materials and

Installation

Installation is “the

same as any paver.”

Richard Calkins,

Project Manager

Manufacturers vary, since each project is contracted. Specifications

call for brick pavers with the truncated dome surface. They are dark

red-brown, as are other sidewalk pavers to define the clear path in the

concrete sidewalk.

The pavers are set on a concrete substrate. Usually the concrete base is

poured, then 1 in of sand, with the brick pavers set into the sand. No

problems are reported with installation since installation is “the same as

any paver.”

Installation at the Towson roundabout is Endicott Brick, installed in

1997-1998. Where the detectable warnings were laid in a brick field,

they are mortared rather than set in sand.

After some informal testing and experimentation, the decision was

made to lay the pavers in a layout aligning the domes, so wheelchair

wheels can travel between them.

Maintenance and

Durability

In traveling in snow

and ice, the least of

his problems was

going over truncated

domes.

Maintenance

No problem has been reported.

To date, there has been minimal experience with snow or ice removal.

The pavers are dark, so the snow melts quickly. Use of chemicals is

planned, as needed. Mr. Calkins stated that in traveling in the snow

and ice, the least of his problems was going over the truncated domes.

Durability

Dome wear was reported to be a minor issue.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 97

Baltimore County, Maryland, continued

Acceptance No instances of problems have been reported.

Before installation, there were concerns about problems for those

wearing high heels; however, it has not been a problem to date.

Comments from individuals who are blind have stated that it’s the

“only thing detectable”.

Contacts Richard Calkins, Project Manager

Commission on Disability

Baltimore County Department

of Public Works

111 W. Chesapeake Ave.

Towson, MD 21204

Phone: (410) 887-3734

E-mail: rcalkins@co.ba.md.us

Dan Witt

Maryland DOT

Baltimore, MD

Phone: (410) 321-2825

FIG. 5-14. A BAND

OF DETECTABLE WARNING PAVERS OUTLINES

THE TRIANGULAR SHAPE

OF THIS CURB RAMP

IN TOWSON, MD.
98 U.S. Access Board  Detectable Warnings: Synthesis

Bay Area Rapid Transit (BART)

History

 

Bay Area Rapid Transit (BART) is a 95-mile, automated rapid transit

system serving over 3 million people in four counties, including San

Francisco County. BART has 12 surface, 13 aerial, and 14 subway

stations. Four stations in downtown San Francisco are shared with the

San Francisco Municipal Railway.

Research on detectable warning surfaces was conducted in the BART

system beginning in 1986 (Peck & Bentzen, 1987).

Since 1987, detectable warnings have been installed throughout the

BART system in all of 39 stations.

The BART safety department found that incidence of falls has

decreased since installation of the detectable warning tiles.

Materials and

Installation

Early installations were Pathfinder Tile, manufactured by Carsonite.

The Pathfinder Tile is a resilient material that was glued to the platform

surface. Installations since 1997 are Armor-Tile.

All are installations are yellow, with black tiles at door locations.

Armor-Tile installations are attached with adhesives and mechanical

fasteners. Two types of Armor-Tile materials have been used. One is

flat (1/2 in) tile, attached in a recessed fashion to the platform surface.

In a few stations, a 3 in thick Armor-Tile product has been used. This

tile replaced the concrete on the platform edge; it was used where there

were problems with the concrete of the platform.

Maintenance Tiles are cleaned on a weekly basis with the stations.

There has been no experience with snow and ice.

Durability The Pathfinder Tile peeled up over time due to weather, platform

vibration and scrubber type cleaning. Many tiles have been replaced

by Armor-Tile.

Color degraded in one instance with tile from a different vendor and

the contractor replaced the faded tile with Armor-Tile.

Acceptance Tiles are very well accepted by the public. No problems are reported.

While Armor-Tile is not resilient, Mr. Nnaji reports better sound

distinction than with the resilient tiles.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 99

Bay Area Rapid Transit (BART), continued

Contact Ike Nnaji, ADA Compliance Officer

BART

800 Madison Street, Oakland, CA 94604

Phone: (510) 464-6173

Fax: (510) 464-6196

E-mail: innaji@bart.dst.ca.us

FIG. 5-15.

DETECTABLE WARNING

SURFACE AT A BART

STATION, CALIFORNIA.
100 U.S. Access Board  Detectable Warnings: Synthesis

Claremont, California

History Detectable warnings have been installed on a trial basis at a roundabout

in Claremont, CA. The temporary installation is at curb-ramps and

median edges and was installed in about October, 1999. Two-foot

wide sections were glued down at the ends of the curb-ramps and in the

middle of the cut-through area of the splitter island.

Mr. Desatnik states: “In a permanent installation, we would probably

try to put the tactile material on both entrances to the cut-through area

of the splitter islands.... It is very important for the blind user to know

exactly where they are in the splitter island.... With the tactile material

at each edge, once they hit the first one, then they know they are in the

safe zone, then when they hit the second strip, they know they are at

the edge of the travel lane and ready to cross the street.”

Materials and

Installation

The detectable warning is a rubber tile product that has been glued

down on the surface of the ramp and median areas, on top of the

existing pavement. A slight lip of approximately 1⁄4 in is caused by the

material thickness.

Maintenance and

Durability

• The material is not cleaned.

• The durability has not really been tested, since the material has

been installed recently.

• There have been no problems with lifting or peeling.

Acceptance

Concerns regarding

a tripping hazard are

“an inflated concern”

Brian Desatnik,

Housing and

Redevelopment

Coordinator

No pedestrian complaints have been received about the detectable

warnings. Mr. Desatnik feels that concerns regarding a tripping hazard

are “an inflated concern”.

Comments from individuals who are blind are very positive about the

detectable warning. These individuals are not happy with the

roundabout design, however they have stated that the detectable

warning helps them know where the median is. Elderly pedestrians are

complaining about the roundabout crossings, but not about the

detectable warning.

Contact Brian Desatnik

Housing & Redevelopment Coord.

City of Claremont

207 Harvard Avenue

Claremont, CA 91711

Phone: (909) 399-5341

Fax: (909) 399-5366

E-mail:

Bdesatnik@ci.claremont.ca.us
U.S. Access Board  Detectable Warnings: Synthesis 101

Chapter 6



U.S. Use of Detectable Warning

Surfaces: Applications

Summary Recommended locations for use of truncated dome detectable

warnings that are currently being considered in the U.S. include curbramps, islands and medians, raised crosswalks, and raised

intersections.

This chapter summarizes and illustrates recent guidelines and

recommendations on the use of detectable warnings in locations other

than transit platforms.

None of the recommendations should be construed to represent

the opinion of the authors or of the Access Board.

Chapter contents This chapter covers the following topics.

 Topic Page

 Sources of recommendations 102

 Recommendations for detectable warnings

at curb-ramps 105

 Detectable warnings at hazardous vehicular ways 109

 Detectable warnings at medians and islands 110

 Detectable warnings at raised crosswalks and

raised intersections 112
102 U.S. Access Board  Detectable Warnings: Synthesis

Sources of recommendations

Purpose of

this chapter

With the exception of the Americans with Disabilities Act

requirement (ADAAG 10.3.1(8)) for 24 in deep truncated dome

detectable warnings at transit platform edges having drop-offs (see

Chapter 2), there is no national requirement in the U.S. for the use of

truncated dome detectable warnings in other locations.

• However, a number of publications that followed ADAAG,

including local and state standards, resolutions of organizations of

and for people who are blind, and a workshop on the topic

conducted by Project ACTION provide recommendations or

guidance on other uses of truncated dome detectable warnings in

locations where pedestrians who are blind do not have a definitive

cue to the end of the pedestrian way.

• These recommendations are summarized and illustrated in this

chapter.

• Readers will note that some of the recommendations are in conflict

with one another.

• None of the recommendations should be construed to

represent the opinion of the authors or of the Access Board.

ADAAG As published in 1991, ADAAG included scoping and technical

provisions for detectable warnings on transit platform edges, curbramps, hazardous vehicular ways and at reflecting pools. The specific

sections in ADAAG are re-printed in Chapter 2. In this chapter (6),

ADAAG requirements for locations other than transit platforms are

illustrated for the sake of comparison with other recommendations.

California Title 24 Title 24, California Code of Regulations is the California accessibility

code. The 1999 edition requires detectable warnings on curb-ramps

having a slope less than 1:15, at hazardous vehicular ways, and on all

transit boarding platforms. The specifications for the detectable

warning are similar to those in ADAAG 4.29.2, but a little more

specific. Detectable warnings at most curb-ramps, at hazardous

vehicular ways, and on transit platforms require a more precisely

specified surface texture: the dome diameter shall be .9 in, measured

at the bottom of the dome, tapering to .45 in at the top. Detectable

warnings on curb-ramps for privately funded housing, at hazardous

vehicular ways, and on transit platforms shall be safety yellow

(Federal color 33538).

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 103

Sources of recommendations, continued

Project ACTION

panel of experts

On June 4-5, 1995, Project ACTION, at the request of the Access

Board, convened a panel of experts to consider the needs of

pedestrians with visual impairments when using intersections. The 22

panel members represented the following constituencies and areas of

expertise.

• Two major organizations of people who are blind

• Orientation and mobility specialists

• Civil engineers

• Transportation engineers

• Assistive technology experts

• Experts in human/ergonomic factors

The panel recommended the use of detectable warnings on curbramps.

Accessible Rights

of Way: A Design

Guide

In November 1999, the U.S. Access Board published Accessible

Rights-of-Way: A Design Guide. This guide contains best practice

recommendations for the design, construction, alteration, and retrofit

of public pedestrian facilities. Detectable warnings are recommended

as one way to make boundaries between sidewalks and streets

perceptible at curb-ramps, at raised crosswalks, and at cut-through

islands. The guide does not provide recommendations for specific

placement and dimensions of the detectable warnings, however.

Designing

Sidewalks & Trails

for Access: Part II.

A Best Practices

Guidebook

Designing sidewalks and trails for access: Part II of II: A best

practices guidebook (Axelson, Chesney, Galvan, Kirschbaum,

Longmuir, Lyons, and Wong) is to be published in late 2000 by the

Federal Highway Administration. This detailed, well-illustrated guide

to best practices for designing accessible sidewalks and trails contains

numerous drawings showing locations for and dimensions of

detectable warnings on curb-ramps, at depressed corners, at cutthrough and ramped medians and islands, and at level railroad

crossings.

ACB Street Design

Guidelines

In 1999 the American Council of the Blind (ACB) produced Street

Design Guidelines, which recommends the placement of 24 in deep

detectable warnings at the bottom of curb-ramps and at locations

where the pedestrian walkway is level with the street. The guidelines

caution against the overuse of detectable warnings, recommending

that the truncated dome surface be used only as a warning, never for

guidance.

Continued on next page
104 U.S. Access Board  Detectable Warnings: Synthesis

Sources of recommendations, continued

Roseville, CA Roseville standard plans require 36 in deep detectable warnings at the

bottom of curb-ramps instead of the full surface of the curb ramp as

required by California Title 24. Precast detectable warning panels are

used.

Cambridge, MA Cambridge specifications require detectable warnings on sidewalks, at

the street edge, at locations with raised crosswalks or raised

intersections.

Austin, TX Austin specifications require detectable warnings on curb-ramps in the

central business district. A 4 x 5 ft section of pavers is used on most

curb-ramps.

Baltimore County,

MD

Baltimore County, MD, specifications call for 32 in deep detectable

warnings at the bottom of curb-ramps including the radius of blended

curbs.

AER resolutions The Association for Education and Rehabilitation of the Blind and

Visually Impaired (AER) adopted resolutions in 1992, 1994 and 1998

calling for the use of detectable warnings. The 1994 and 1998

resolutions specifically called for a 24 in deep detectable warning at

the bottom of curb-ramps.

ACB resolutions The American Council of the Blind (ACB) adopted resolutions in

1994, 1995, 1996 and 1998, favoring the use of detectable warnings.

ACB resolutions in 1995 and 1996 requested the placement of

detectable warnings on the bottom 24 in of curb-ramps. A resolution

passed in 1994 called for detectable warnings at level track crossings.

NFB resolutions The National Federation of the Blind (NFB) adopted resolutions in

1992, 1993, 1994 and 1995 opposed to the installation of truncated

dome detectable warnings because they were considered to be costly,

not necessary, and possibly harmful to the independent mobility of

blind pedestrians.
U.S. Access Board  Detectable Warnings: Synthesis 105

Recommendations for detectable warnings at curb-ramps

Whole surface

of ramp—

ADAAG

FIG. 6-1. ADAAG

DETECTABLE WARNING

DESIGN (TEMPORARILY

SUSPENDED).

FIG. 6-2. SPLITTER

ISLAND WITH DETECTABLE WARNING ON FULL

SURFACE OF CURB

RAMP, AUSTIN, TX.

ADAAG originally required detectable warnings on the full surface of

curb-ramps. Flares were not required to have detectable warnings.

detectable warning

Flared side Curb-ramp with

Sidewalk

Continued on next page
106 U.S. Access Board  Detectable Warnings: Synthesis

Recommendations for

detectable warnings at curb-ramps, continued

Whole surface

of ramp—

California Title 24

“The only legal action

related to detectable

warnings in California

has been one

threatened suit in W.

Sacramento. A

bicyclist was injured.

The city was not

considered liable

because the domes

were required by

state law.” Michael

Mankin, AIA, CA

office of the State

Architect.

FIG. 6-3. CURB-RAMP

DESIGN REQUIRED BY

CALIFORNIA TITLE 24.

Since 1994, California Title 24 has required detectable warnings on

the full surface of curb-ramps having slopes less than 1:15. The

detectable warning on transit platforms must be safety yellow (Federal

Color No. 33538).

The California specifications for the detectable warning texture for

curb-ramps and transit platforms are more precise than those in

ADAAG, specifying that the 0.9 in dome diameter is to be measured

at the base of the dome, and the top diameter is to be 0.45 in. The

2.35 in dome spacing is to be measured on the diagonal of a square

pattern of domes.

California has also required a 1⁄2 in beveled lip at the lower end of each

curb ramp since 1982. The requirement for the 1⁄2 in beveled lip was

the result of extensive consultation involving both pedestrians who are

blind and people who use wheelchairs as a mobility aid. The 1⁄2 in

beveled lip was to indicate to pedestrians who are blind the location of

the bottom of the ramp, and the lip was not considered to make curbramps inaccessible to people who use wheelchairs.

California Title 24 also requires a grooved border 12 in wide at the

level surface of the sidewalk along the top and each side. The grooves

are approximately 3⁄4 in on center.

detectable warning

Flared side Curb ramp with

Grooved border

Sidewalk

1/2"

beveled

lip

Bottom 3 feet—

Roseville, CA

The City of Roseville, CA requires that a 3 ft deep strip of detectable

warning surface extend the width of the curb-ramp.

See Figure 5-9 in the Roseville Case Study.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 107

Recommendations for detectable warnings at curb-ramps

Bottom 2 feet—

multiple sources

FIG. 6-4. CURB RAMP

DESIGNS SHOWING

24 IN DETECTABLE

WARNING.

Placing detectable warnings only on the bottom 2 ft of curb-ramps has

been recommended in a number of sources.

• The panel of experts convened by Project ACTION at the request of

the Access Board, on June 4-5, 1995, recommended that 24 in

deep detectable warnings be placed at the bottom of curb-ramps.

• The same recommendation is made in Designing sidewalks and

trails for access: Part II of II: A best practices guidebook

(Axelson, et al., 2000, FHWA).

• Multiple resolutions passed by the AER and by the ACB have also

called for 24 in deep detectable warnings at the bottom of curbramps.

• All of these sources suggest that parallel alignment of the

truncated domes may make it easier for people with mobility

impairments, especially those who use wheelchairs, to use curbramps having detectable warnings.

detectable warning

Flared side Curb ramp with

Sidewalk

24610

Flared side

Sidewalk

2

610

4

Curb ramp with

detectable warning

Continued on next page
108 U.S. Access Board  Detectable Warnings: Synthesis

Recommendations for

detectable warnings at curb-ramps, continued

Parallel curb-ramp

 Detectable

 warning

Sidewalk

24

610

Slope down Level Slope down

FIG. 6-5. PARALLEL CURB-RAMP DESIGN SHOWING

RECOMMENDED 24-INCH DETECTABLE WARNING.
U.S. Access Board  Detectable Warnings: Synthesis 109

Detectable warnings at hazardous vehicular ways

California Title 24

FIG. 6-6. A BLENDED

CURB WITH A DETECTABLE WARNING AT A

WIDE CORNER RADIUS.

.

FIG. 6-7. A

DETECTABLE WARNING

DEFINING THE LIMIT OF

THE SAFE WAITING AREA

IN FRONT OF A HOTEL

THAT HAS NO CURB

DEFINING THE EDGE OF

THE PEDESTRIAN AREA.

California Title 24 requires that “If a walk crosses or adjoins a

vehicular way, and the walking surfaces are not separated by curbs,

railings or other elements between the pedestrian areas and vehicular

areas, the boundary between the areas shall be defined by a continuous

detectable warning which is 36 inches (914 mm) wide....” It must be

safety yellow.

Several types of hazardous vehicular ways are shown below.

36" deep

detectable warning

at blended curb

Sidewalk

Street

Street

Pedestrian area

Hotel

No change

in level

or slope

Vehicular area

36" deep detectable warning
110 U.S. Access Board  Detectable Warnings: Synthesis

Detectable warnings at medians and islands

Cut-through

medians

FIG. 6-8. DETECTABLE

WARNINGS USED AT

CUT-THROUGH MEDIANS.

Placement of detectable warnings on cut-through medians varies

with the width of the median.

• Designing sidewalks and trails for access: Part II of II: A best

practices guidebook (Axelson, et al., 2000, FHWA) recommends a

24 in deep detectable warning at each side of the cut-through

walking surface.

• There is no U.S. recommendation that deals with narrow medians,

however United Kingdom guidelines (Guidance on the Use of

Tactile Paving Surfaces, 1998) recommend that on medians no

more than 4 ft wide, the detectable warning should cover

the entire depth and width of the cut-through.

• Medians that have curb-ramps should have detectable warnings

following the guidelines for curb-ramps.

24

48

>48

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 111

Detectable warnings at medians and islands, continued

Cut-through

splitter islands

FIG. 6-9. SPLITTER

ISLAND: PEDESTRIAN

PASSAGE THROUGH THE

ISLAND IS AT THE SAME

LEVEL AS THE STREET.

DETECTABLE WARNING

IS SHOWN AT EACH END

OF CUT-THROUGH

WALKING SURFACES.

Designing sidewalks and trails for access: Part II of II: A best

practices guidebook (Axelson, et al., 2000, FHWA) recommends a 24

in deep detectable warning at each end of all cut-through walking

surfaces.

This is also recommended in the United Kingdom publication,

Guidance on the Use of Tactile Paving Surfaces (1998).

Passage at street level with

24" deep detectable warning

Sidewalk

Right turn lane

Street

Street

Splitter

island
112 U.S. Access Board  Detectable Warnings: Synthesis

Detectable warnings at

raised crosswalks & raised intersections

Raised crosswalks

& raised

intersections

Designing sidewalks and trails for access: Part II of II: A best

practices guidebook (Axelson, et al., 2000, FHWA) recommends a 24

in deep detectable warning on the sidewalk at each end of raised

crosswalks.

This design is required by Cambridge, MA specifications.

FIG. 6-10. AT LEFT, A

RAISED INTERSECTION.

AT RIGHT, A RAISED

CROSSWALK SHOWN

AT MIDBLOCK

.

Up Up Up

Up

Up

Up

Street

Sidewalk

Detectable warning

Vehicle ramp up

A raised intersection is a traffic calming element that has flat raised

areas covering the entire intersection, including adjoining crosswalks,

with vehicle ramps on all street approaches. A raised intersection is

also known as a raised junction, intersection hump, table, or plateau.

Fitting to a blended

curb at a raised

intersection

Installing detectable warnings around a corner radius can be

accomplished in two ways.

• In Towson, MD, brick pavers are cut into a trapezoidal shape and

then fitted together (see Case Study: Baltimore County).

• Alternatively, they can be splayed apart (see Fig. 7-5).

• Either design results in some domes being closer than others are.

Small irregularities in dome spacing do not appear to decrease

detectability (Bentzen et al., 1993).

FIG. 6-11. DESIGN DRAWING SHOWING CUTTING PATTERN

FOR BRICK DETECTABLE WARNING PAVERS AT THE RADIUS

CURB LINE OF A RAISED CROSSWALK (TOWSON, MD).
U.S. Access Board  Detectable Warnings: Synthesis 113

Chapter 7



U.S. Detectable Warning Products

Summary This chapter includes information on detectable warning products that

are produced in the U.S. Information in this chapter is based on

research and telephone interviews conducted in late 1999 through

April 2000.

Only products and tooling systems generally complying with ADAAG

technical provisions for truncated dome detectable warnings are

included.

Chapter contents This chapter covers the following topics:

 Topic Page

 Spacing of truncated domes 114

 Shape of truncated domes 116

 Types of detectable warning products 117

 Dimensional pavers 118

 Thin tiles and sheet goods 119

 On-site fabrication of truncated dome surfaces 120

 Characteristics of detectable warning products 123

 Detectable warning product matrix 125

 Photographs of detectable warning products 126

 Detectable warning manufacturers 132

 
114 U.S. Access Board  Detectable Warnings: Synthesis

Spacing of truncated domes

Manufacturing

standards

In complying with the Americans with Disabilities Act Accessibility

Guidelines (ADAAG), manufacturers have adopted various dome

configurations to accommodate existing industry-standard sizes of

paving products

ADAAG technical

specification

The ADAAG 4.29.2 (1991)

specification for a detectable warning

surface is an array of truncated domes.

(See the full specification at the

beginning of Chapter 2.)

ADAAG includes no illustration of the

truncated dome profile or of the dome

pattern. It also does not specify where

required dimensions are measured.

However, the Access Board issued

Detectable Warnings Bulletin #1 in

1993 to provide additional guidance.

A figure in this bulletin shows spacing

(2.35 in) measured diagonally.

Another figure shows the .9 in dome

diameter applied to the base of the

domes.

FIG. 7-1. DOME SPACING

CAN BE MEASURED EITHER

(ADJACENT) PARALLEL (P) OR

DIAGONALLY (D).

Brick pavers Detectable warning brick pavers must

conform to the relatively small 4 in x

8 in module to be compatible with the

industry standard for flat surface

pavers.

Four manufacturers have handled the

truncated dome spacing in an identical

manner:

• Adjacent spacing = 2.00 in

• Diagonal spacing = 2.82 in

This is a slightly larger dome to dome

spacing than is typically found for

larger tiles.

FIG. 7-2. HERRINGBONE BOND

WITH DETECTABLE WARNING

BRICK PAVERS.

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 115

Spacing of truncated domes, continued

Pattern repetition Most detectable warning

products are configured so that

repeating a single unit (tile,

paver, or sheet) will result in a

continuation of the ADAAGspecified pattern of truncated

domes. A gap in pattern

between adjacent tiles does not

impair detectability (Bentzen

et al., 1993). FIG. 7-3. TYPICAL 12”X12” TILES.

Complementary

tile pairs

One manufacturer (Crossville Ceramics)

produces a detectable warning tile system

consisting of two complementary tile pairs:

• Type A tile (rows of 3-2-3-2-3 domes)

• Type B tile (rows of 2-3-2-3-2 domes)

Type A tiles are used in conjunction

with Type B tiles to produce an unbroken,

repeating pattern.

FIG. 7-4. COMBINATION

OF 12 AND 13 DOME

TILES.

Working with

irregular shapes

Fitting square modular pavers within the irregular shape of a radius

curb line can be a challenge. Systems with field-applied truncated

domes can accommodate to irregular surfaces and to irregular

boundaries.

Figure 7-5 shows how detectable warning pavers can be splayed to

match the radius of a street boundary.

FIG. 7-5. SPLAYED

12 IN TILES ON AN

8 FT TO 10 FT RADIUS.

Flush curb

Street

Detectable

warning

Sidewalk
116 U.S. Access Board  Detectable Warnings: Synthesis

Shape of truncated domes

Truncated dome

diameter

There are two ways to conform to ADAAGs dome size specification:

Generally U.S. manufacturers apply the required 0.9 in dimension at

the truncated dome base.

Two products conform by applying the dimension to the flattened

dome top.

Figure 7-6 illustrates how domes with different base diameters

conform to ADAAG. The dome on the right has a base diameter of

1.25 in.

FIG. 7-6. APPLYING DOME DIMENSION GUIDELINES.

Manufacturers’

response

The ADAAG specification is open to a number of interpretations. In

part, this explains why currently available detectable warning products

vary considerably in appearance.

FIG. 7-7. FULL-SCALE CROSS SECTIONS OF

TRUNCATED DOMES FROM VARIOUS PRODUCTS.
U.S. Access Board  Detectable Warnings: Synthesis 117

Types of detectable warning products

Summary Detectable warning products are produced using a variety of

manufacturing processes and materials.

• Natural stone and stone composites

• Brick and concrete

• Rigid polymer and flexible polyurethane sheets and tiles

• Large precast assemblies

• Tools to produce the warning surface in wet concrete

• Surface applied domes used with membrane decking

Each product type is discussed in this chapter. Manufacturers’ names

are included in parentheses.

Use of term

“detectable

warning”

This publication uses the term “detectable warning” to mean the

walking surface consisting of truncated domes as specified ADAAG.

A number of other textured surfaces are used for flooring and paving.

These are not highly detectable and are not comparable in usability to

truncated domes.

Rely on current

specifications

Persons selecting detectable warning products should rely on current

specifications. Manufacturer’s product literature may feature products

that comply with out-of-date specifications such as ANSI A117.1-

1986, which has been superceded by ANSI A117.1-1998.

Details should

be verified

This chapter discusses detectable warning products available in the

U.S. at the time of writing. The discussion is based on sales/technical

literature and product samples, and is an introduction to the wide

variety of material types that are offered. Far more options are

available than can be suggested in this brief space.

All product specifications should be verified with their respective

manufacturers for accuracy and current availability.
118 U.S. Access Board  Detectable Warnings: Synthesis

Dimensional pavers

Definition Dimensional pavers as discussed in this section include all products

that are sufficiently thick to require that they be recessed into the

platform, sidewalk, or curb ramp.

These products vary in thickness from 1⁄2 in to 3 or 4 in.

Natural stone,

stone composites,

& ceramic tile

 

Paving stones manufactured with a truncated dome surface are

available in natural granite (Cold Spring Granite) and a similar

looking product made of reconstituted granite (Ryowa from

Architectural Tile & Granite) which is pressed and fired at high

temperature.

Crushed limestone and granite pavers are available (Hanover) as two

inch thick pavers in nominal 12 in x 12 in, 24 in x 24 in, and

24 in x 36 in sizes.

Detectable warning products marketed as ceramic tiles and

porcelain stone tiles (Summitville and Crossville) are designed to be

used in conjunction with a wide range of modularized flooring tile

systems.

Brick pavers

 

Brick and concrete brick pavers that incorporate truncated domes are

produced in nominal 4 in x 8 in sizes. This includes pavers measuring

an actual 4 in x 8 in, and those that are 3 5/8 in x 7 5/8 in that include

a mortar allowance. Thicknesses vary from 1⁄2 in to 21⁄4 in.

Detectable warning brick pavers (and concrete brick pavers) have a

uniform spacing of truncated domes that allows the bricks to be laid in

a running bond, stack bond, or herringbone pattern (See Fig. 7-2).

Large precast units Large precast concrete units are available for detectable warning

surfaces. One manufacturer (Steps Plus) makes a 3 ft square sidewalk

unit, and a curb ramp unit with ramp and flared sides cast in concrete

as a single unit.

Durability of domes has been reported as a problem with some

concrete products (see Chapter 5).

One composite stone product (Hanover) mentioned above also

markets detectable warning pavers up to 2 ft x 3 ft in dimension.
U.S. Access Board  Detectable Warnings: Synthesis 119

Thin tiles & sheet goods

Definition Thin tiles and sheet goods are discussed in this section. This

grouping includes those products that are a nominal 1/8 in thick.

These products may be applied to the surface of a new or existing

platform, sidewalk, or curb ramp. Often these products are available

with a beveled edge to make a smoother transition to adjoining

surfaces.

Rigid &

flexible product

composition

Two manufacturers (ADA Fabricators and Engineered Plastics)

supply rigid tiles or panels of polymer composition. The material is

described as:

• Glass and carbon reinforced copolymer composite, or

• Vitrified Polymer Composite (VPC).

One supplier (Disability Devices Distributor) offers a flexible tile or

mat described as:

• Flexible polyurethane.

Tile size Applied tiles or panels with truncated domes are available in a variety

of sizes including: 12 in x 12 in; 24 in x 24 in; 24 in x 36 in; and

24 in x 48 in.

These products are a nominal 1/8 in thickness (exclusive of the height

of the truncated domes).

Armor-Tile (Engineered Plastics) also has a second detectable

warning product available with truncated domes of 0.9 in top diameter

and 1.325 in base diameter. This distinctive product has dome

spacing closely resembling that used on the 4 in x 8 in brick pavers.

Installation Surface applied tiles are secured to the substrate with a structural

adhesive system. Two products (Engineered Plastics and Disability

Devices Distributor) are available with optional mechanical fasteners

that function as anchors into the supporting surface.

In addition, two of these manufacturers offer a thick composite shell

product that can be filled with concrete and installed similar to a

paving stone.
120 U.S. Access Board  Detectable Warnings: Synthesis

On-site fabrication of truncated dome surfaces

Definition Several detectable warning products consist of systems that are

fabricated on-site. Three different approaches are used:

• Truncated domes produced by molding or stamping the top

surface of freshly poured concrete

• Individual truncated domes transferred from a carrier sheet to

new or existing platform, sidewalk, or curb ramp.

• Domes “flowed” onto a surface guided and formed by a fixed or

moveable template.

On-site production

of domed surface

Individual truncated domes may be applied to an existing surface,

often concrete, sometimes metal. Fig. 7-8 shows an example of a

truncated dome surface being created on-site.

Domes are produced from a catalyzed carboxylated latex emulsion.

The field between domes (if used) is a latex vinyl copolymer applied

by roller.

 

FIG. 7-8. APPLICATOR MACHINE IS PULLED

AT STEADY SPEED AS MATERIAL FROM THE

HOPPER IS PLACED AS TRUNCATED DOMES

ON PLATFORM SURFACE BELOW

(STRONGWALL).

FIG. 7-9. COMPLETED

DETECTABLE WARNING

APPLICATION AT RAILROAD PLATFORM

(STRONGWALL).

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 121

On-site fabrication of truncated dome surfaces, continued

Stamped concrete Local concrete contractors use stamping tools to produce raised

truncated domes on the surface of freshly poured concrete

(Cobblecrete and Increte).

A high-quality surface can only be obtained with a skillful installer.

See Chapter 5 for case study discussions of problems of casting

truncated domes on a sloping surface. Quality control is necessary

to prevent premature dome wear.

FIG. 7-10.

ONE PROCEDURE

FOR PRODUCING

STAMPED CONCRETE

(INCRETE SYSTEMS).

These on-site procedures for producing

truncated domes are an extension of an

existing technology which is widely

used to impart textures to concrete

surfaces to resemble slate, brick, flagstone, and so forth.

Concrete may be integrally colored, or

have mineral pigments broadcast over

the surface, or both.

The stamping tool may be rigid or

flexible, and made of rubber or

polyurethane. This tool is pressed into

the concrete surface with sufficient

force to create the pattern of truncated

domes.

After the concrete surface has partially

cured, a clear sealer is brushed on.

Detectable

warnings that

are not on grade

FIG. 7-11. TRUNCATED

DOMES APPLIED TO A

WOODEN RAILROAD

PLATFORM (COTE-L).

The surface-applied truncated

dome products have a special

advantage when a detectable

warning surface is required on

a flexible surface such as a

wooden deck above grade.

The applied dome products are usually installed in conjunction with a

membrane coating surface. This provides added traction on a surface

such as wood that can become slippery when wet.

Continued on next page
122 U.S. Access Board  Detectable Warnings: Synthesis

On-site fabrication of truncated dome surfaces, continued

Surface-applied

dome products

FIG. 7-12.

SURFACE-APPLIED

TRUNCATED DOMES

SHOWN CONFORMING TO

IRREGULAR SURFACE

(VANGUARD / TILCO).

FIG. 7-13. (LEFT)

TRUNCATED DOMES ARE

ARRAYED ON A CARRIER

SHEET (COTE-L).

FIG. 7-14. (RIGHT)

DOMES SHOWN

ADHERED TO PLATFORM

SURFACE. A SAFETY

YELLOW POLYURETHANE COATING IS BEING

APPLIED (COTE-L)

Individual truncated domes may be applied to an existing surface,

often concrete or bituminous.

The domes of the Vanguard product (Tilco) may be applied to a

surface as shown in Fig. 7-12. The underlying surface is not

otherwise coated in this installation. Vanguard also offers a concrete

micro-coating system which can be applied to the domes and

immediately surrounding surface. This coating provides a high level

of visual contrast in white or safety yellow.

In one product application (COTE-L), a polyurethane coating is

applied to the underlying surface. The coating includes rubber

granules that give increased friction and resilience. Rubber truncated

domes, which come attached to a carrier sheet, are pressed on top of

the fresh polyurethane coating. The plastic carrier sheet is peeled off,

and three additional coats of polyurethane coating are applied.

 
U.S. Access Board  Detectable Warnings: Synthesis 123

Characteristics of detectable warning products

Slip resistance Products use several methods to improve traction and reduce potential

pedestrian slipping incidents:

• Glass beads embedded in the domes and/or a surface coating

• Small raised bumps molded onto the field surface and dome

surface of rigid polymer products

• A gritty applied traction coating

• Raised concentric circles on dome top

Color Manufacturers offer detectable warning products in a wide range

of standard and custom colors.

ADAAG requires that detectable warnings contrast with adjacent

surfaces, but it does not specify a particular color. Research indicates

that standardized safety yellow is especially visible, and it is strongly

preferred by many people having low vision (Bentzen et al.,1995;

Hughes, 1995). A number of products are available in safety yellow.

Some products are available in a more muted yellow or buff color.

A traditional brick red color can be obtained by using traditional brick

detectable warning pavers, concrete pavers with integral red color, or

stamped concrete with red mineral pigments applied to wet concrete.

Traditional granite colors are available by using actual granite, or

composite stone pavers that incorporate granite aggregates. In

Atlanta, a polymer detectable warning material was matched to

existing granite when this became an architectural requirement (see

MARTA case study in Chapter 5).

Color is required by ADAAG to be integral to the product. Some

products meet this requirement through the roller application of a

heavy coating of pigmented pedestrian decking material. This should

not be confused with surface painting.

Contrast ADAAG (4.29.2) requires that the detectable warning surface contrast

visually with adjoining surfaces, and the ADAAG Appendix to that

document recommends that the materials should contrast by at least

70%.

Many products come in a wide range of colors from light grays and

tans to dark red and blacks. Contrast at curb-ramps helps pedestrians

with low vision recognize curb-ramps, and it helps in directing all

pedestriansespecially those of short staturetoward the opposite

corner.
124 U.S. Access Board  Detectable Warnings: Synthesis

Characteristics of detectable warning products, continued

Sound on

cane-contact

& resiliency

Detectable warning surfaces may also differ in resiliency from the

adjoining platform, street, or sidewalk surface. This aids detectability

under foot and with a long cane. One product (COTE-L) uses rubber

domes that are inherently resilient. Another resilient product is

flexible polyurethane tile (Disability Devices Distributor).

One product (Armor-Tile) has a series of raised bosses on the lower

side of the tile. The purpose of these is to allow the tile to be

supported without full adhesive coverage. This in turn produces a

“hollow” sound that is detectable by a blind person using a long cane

(Bentzen & Myers, 1997).

Durability The durability of detectable warning products, particularly of the

raised truncated domes, is an important concern.

Over the years, a number of jurisdictions have conducted laboratory

and field tests of detectable warning products. In Chapter 3, refer to

the section titled “Evaluation of detectable warning materials.”

For additional discussion, see the case studies in Chapter 5.

Each case study covers durability and maintenance.
U.S. Access Board  Detectable Warnings: Synthesis 125

Detectable warning product matrix

MANUFACTURER

/ SUPPLIER MATERIAL 

TYPE / COLOR

Natural & 

pressed stone

ConcreteBrickCeramic/

porcelain tile

Pol

ymer / 

pol

ymer conc.

Flexible 

pol

yurethane

Rubber & otherSafet

y

yellow

DOME 

GEOMETRY

Dia

gonal ali

gnment

Parallel ali

gnment

0.9” dome base diam.0.2” dome hei

ght

Dome s

pacin

g

INSTALLATIONRecessed materialSurface applied

DIMENSIONAL

Cold Spring Granite • •••• A •

Arch. Tile & Granite • • •••• A •

Hanover Arch. Prods. • • •• A •

Steps Plus • • •• A •

Summitville Tiles • • •• A •

Crossville Ceramics • • •• A •

Endicott Clay Prods. • ••• B •

Whitacre-Greer • ••• B •

Superock Block • ••• B •

PAVESTONE • ••• B •

Castek / Transpo • • • C • A •

THIN PAVERS

ADA Fabrications • • • •• A • •

Engineered Plastics • • •••• A • •

Disability Devices • • • •• A •

APPLIED DOMES

Vanguard-Tilco • • • DDA •

COTE-L • • • •• A •

Strongwall • • • •• A •

STAMPED IN PLACE

Cobblecrete • • A •

Increte Systems • • A •

Notes: Some manufacturers market

products in addition to those noted above.

A. Adjacent spacing: 1.66” on center

Diagonal spacing: 2.35” on center

B. Adjacent spacing: 2.00” on center

Diagonal spacing: 2.82” on center

C. 0.90” dome top diameter

D. 1.1” dome base diameter;

0.15” dome height.
126 U.S. Access Board  Detectable Warnings: Synthesis

Photographs of detectable warning products

Sample

photography

The photographs in this section are of product samples provided by

the manufacturer. All products are shown at the same magnification.

Some manufacturers have more detectable warning products than are

illustrated here. Many of the products come in a variety of sizes and

thicknesses. The photographs here may not reflect product size;

the sample may be cut from a larger paver block or sheet.

Note that the products which require placing truncated domes on an

existing walking surface substrate are shown applied to a backing

material (plywood or sheet plastic) which is not part of the product.

FIG. 7-15.

COLD SPRING

GRANITE COMPANY

R & S TRUNCATED

DOMES FINISH, IN

SIERRA WHITE.

FIG. 7-16.

ARCHITECTURAL TILE

& GRANITE, INC.

RYOWA PRESSED STONE

PAVER - BRAILLE

SERIES, DOME TACTILE

TYPE WITH DIAGONAL

ROW.
U.S. Access Board  Detectable Warnings: Synthesis 127

Photographs of detectable warning products, continued

FIG. 7-17.

HANOVER

ARCHITECTURAL

PRODUCTS, INC.

RECONSTITUTED

PRESSED LIMESTONE &

GRANITE DETECTABLE

WARNING PAVER.

FIG. 7-18.

STEPS PLUS, INC.

PRECAST REINFORCED

CONCRETE.

FIG. 7-19.

SUMMITVILLE

TILES, INC.

TACTILE-TREAD

CERAMIC TILE.
128 U.S. Access Board  Detectable Warnings: Synthesis

Photographs of detectable warning products continued

FIG. 7-20.

CROSSVILLE CERAMICS

COMPANY, L.P.

A301 TAC TILE.

FIG. 7-21.

ENDICOTT CLAY

PRODUCTS CO.

HANDICAP DETECTABLE

WARNING PAVER.

FIG. 7-22.

WHITACRE-GREER

FIREPROOFING CO.

DETECTABLE WARNING

PAVER.
U.S. Access Board  Detectable Warnings: Synthesis 129

Photographs of detectable warning products continued

FIG. 7-23.

CASTEK, INC.

PRECAST POLYMER

CONCRETE TILE.

FIG. 7-24.

ADA

FABRICATORS, INC.

COPOLYMER COMPOSITE

TILE.

FIG. 7-25.

ENGINEERED

PLASTICS, INC.

ARMOR-TILE ADA

EPOXY POLYMER

COMPOSITE TILE.
130 U.S. Access Board  Detectable Warnings: Synthesis

Photographs of detectable warning products continued

FIG. 7-26.

ENGINEERED

PLASTICS, INC.

ARMOR-TILE STANDARD

EPOXY POLYMER

COMPOSITE TILE.

FIG. 7-27.

DISABILITY DEVICES

DISTRIBUTOR

POLYURETHANE

DETECTABLE WARNING

MAT.

FIG. 7-28.

VANGUARD ADA

PRODUCTS OF AMERICA,

TILCO, INC.

APPLIED TRUNCATED

DOMES (SHOWN ON

BLACK SHEET ACRYLIC

BACKING FOR SAMPLE

ONLY).
U.S. Access Board  Detectable Warnings: Synthesis 131

Photographs of detectable warning products continued

FIG. 7-29.

COTE-L

INDUSTRIES, INC.

SAFTI-TRAX APPLIED

RUBBER DOMES &

DURABACK

POLYURETHANE

COATING (SHOWN ON

PLYWOOD BACKING

FOR SAMPLE ONLY).

FIG. 7-30.

STRONGWALL

INDUSTRIES, INC.

APPLIED LATEXMODIFIED MORTAR

DOMES & TRAFFIC DECK

MEMBRANE SYSTEM

(SHOWN ON PLYWOOD

BACKING FOR

SAMPLE ONLY).
132 U.S. Access Board  Detectable Warnings: Synthesis

Detectable warning manufacturers

The manufacturers listed below offer

truncated dome detectable warning products.

ADA Fabricators, Inc.

P.O Box 179, N. Billerica, MA 01862

[Copolymer composite tile]

Phone: (978) 262-9900, (800) 372-0519

Fax: (978) 262-1455

Architectural Tile and Granite, Inc.

P.O. Box 3542, Sunriver, OR 97707

[Ryowa Braille Series

reconstituted granite paver]

Phone / Fax: (541) 593-1790

Castek Division, Transpo Industries, Inc.

20 Jones Street, New Rochelle, NY 10801

[Step-Safe precast polymer concrete tile]

Phone: (800) 321-7870 or (914) 636-1000

Fax: (914) 636-1282

Cobblecrete International, Inc.

485 West 2000 South, Orem, UT 84058

[TurboMat (roller) for on-site texturing]

Phone: (800) 798-5791 or (801) 224-6662

Fax: (801) 225-1690

E-mail: cobble@burgoyne.com

Web: www.cobblecrete.com

COTE-L Industries, Inc.

1542 Jefferson St., Teaneck, NJ 07666

[Safti-Trax applied rubber domes

& Duraback polyurethane coating]

Phone: (201) 836-0733

Fax: (201) 836-5220

E-mail: cotel@sprynet.com

Web: www.cotelind.com

Cold Spring Granite Company

202 South 3rd Ave.

Cold Spring, MN 56320

[Granite paver]

Phone: (320) 685-3621, (800) 328-7038

Fax (320) 685-5490

Web: www.coldspringgranite.com

Crossville Ceramics Co., L.P.

P.O. Box 1168, Crossville, TN 38555

[Porcelain stone tile]

Phone: (931) 484-2110

Fax: (931) 484-8418

E-mail: crossc@crossville.com

Web: www.crossville-ceramics.com

Disability Devices Distributor

17420 Mount Hermon St. #C

Fountain Valley, CA 92708

[Polyurethane Detectable Warning Mat]

Phone: (714) 437-9237, (800) 747-5651

Fax: (714) 437-9309

Endicott Clay Products Co.

PO Box 17, Fairbury, NE 68352

[Handicap Detectable Warning Paver, brick]

Phone: (402) 729-3315

Fax: (402) 729-5804

E-mail: endicott@endicott.com

Web: www.endicott.com

Engineered Plastics Inc.

Olympic Towers, 300 Pearl Street, Suite 200

Buffalo, NY 14202

[Armor-Tile epoxy polymer composite]

Phone: (800) 682-2525 or (716) 842-6039

Fax: (800) 769-4463

Web: www.engplastics.com

Continued on next page
U.S. Access Board  Detectable Warnings: Synthesis 133

Detectable warning manufacturers, continued

Hanover Architectural Products, Inc.

240 Bender Rd., Hanover, PA 17331

[Reconstituted pressed limestone &

granite Detectable Warning Paver]

Phone: (717) 637-0500

Fax: (717) 637-7145

Web: www.hanoverpavers.com

Increte Systems

Inco Chemical Supply Co., Inc.

8509 Sunstate St., Tampa, FL 33634

[Stamping tools for ADA Tactile

Detectable Warning Systems]

Phone: (800) 752-4626, (813) 886-8811

Fax: (813) 886-0188

Web: www.increte.com

Pavestone Company

4835 LBJ Freeway, Suite 700

Dallas, TX 75244

[Concrete detectable warning paver]

Phone: (800) 245-PAVE, (972) 404-0400

Fax (972) 404-9200

E-mail: info@pavestone.com

Web: www.pavestone.com

Steps Plus, Inc.

6375 Thompson Rd., Syracuse, NY 13206

[Precast reinforced concrete

Detectable Warning Units]

Phone: (315) 432-0885

Fax: (315) 432-0612

Web: www.steps-plus.com

Strongwall Industries, Inc.

P.O. Box 201, Ridgewood, NJ 07451

[Applied latex-modified mortar domes

& traffic deck membrane system]

Phone: (800) 535-0668 or (201) 445-4633

Fax: (201) 447-2317

Web: www.strongwall.com

Summitville Tiles, Inc.

P.O. Box 73, Summitville, OH 43962

[Tactile-Tread ceramic tile]

Phone: (330) 223-1511

Fax: (330) 223-1414

Web: www.summitville.com

Superock Block Company Inc.

3301 27th Avenue N, P O Box 5326

Birmingham, AL 35207-0326

[Compressed concrete StoneScape

Detectable Warning Paver]

Phone: (205) 324-8624

Fax: (205) 324-8671

http://ggunn@lehighcement.com

Vanguard ADA Products of America

Tilco, Inc.

20628 Broadway Avenue,

Snohomish, WA 98296

[Applied truncated domes]

Phone: (800) 290-5700

Fax: (360) 668-3335

E-mail: tilcovngrd@aol.com

Web: www.vngrd.com

Whitacre-Greer Fireproofing Company

1400 S. Mahoning Avenue,

Alliance, OH 44601

[Detectable warning ADA Brick]

Phone: (800) WGPAVER, (330) 823-1610

Fax: (330) 823-5502

E-mail: Info@wgpaver.com

Web: www.wgpaver.com

The following companies do not currently

offer ADA detectable warning products.

Their names appear on earlier supplier lists:

Advantage Metal High Quality Tactile

American Olean Lanxide (SMC)

Bomanite Rehau, Inc.

Carsonite (Pathfinder) Roppe Corp.

Daltile Corp. Specialty Concrete

Goria Enterprises Synertech Molded

Hastings Pavement Terra Clay Prodcts
134 Use of Tactile Warning Surfaces
U.S. Access Board  Detectable Warnings: Synthesis 135

Appendix

Summary The Appendix includes combined references / annotated bibliography,

and a glossary of terms used in the text. A copy of the questionnaire

used in interviews regarding detectable warning installations is also

included.

Appendix contents The Appendix has the following sections.

 Topic Page

 References and Annotated Bibliography 136

 Glossary 147

 Questionnaire for interviews regarding

detectable warning installations

148

 
136 U.S. Access Board  Detectable Warnings: Synthesis

References and Annotated Bibliography

Annotations emphasize only the portions of each

publication which are most relevant to this synthesis.

Accessible rights-of-way: A design guide. (1999). Washington, DC: U.S. Architectural and

Transportation Barriers Compliance Board.

A comprehensive overview of the Americans with Disabilities Act and its application to

public rights-of-way. Contains detailed suggestions for making public rights-of-way

accessible. Suggests detectable warnings as a way to make information about

pedestrian/vehicular boundaries perceptible to persons who are visually impaired.

Aiello, J. & Steinfeld, E. (1980). Accessible buildings for people with severe visual impairment.

Washington, DC: US Department of Housing and Urban Development, Office of Policy

Research, Report No. HUD-PDR-404.

First U.S. research on warning surfaces. A ribbed rubber mat was found to be highly

detectable to eight blind subjects travelling with a long cane, when they approached it from

brushed concrete.

American national standard: Accessible and usable buildings and facilities CABO/ANSI

A117.1-1992. (1992). Falls Church, VA: Council of American Building Officials.

The only standard regarding detectable warnings is that they shall be standard within a

building, facility, site, or complex of buildings. Contains no technical specification for

detectable warnings.

American national standard: Accessible and usable buildings and facilities ICC/ANSI A117.1-

1998. (1998). Falls Church, VA: International Code Council.

Provides standards for truncated dome detectable warnings—similar to ADAAG 4.29.2.

Provides use of other surfaces or technology that ensure equivalent detectability.

American national standard: Specifications for making buildings and facilities accessible to and

usable by physically handicapped people ANSI A117.1-1980. (1980). New York: American

National Standards Institute, Inc.

The first U.S. standard for tactile warning surfaces on curb ramps, preceding hazardous

vehicular ways, preceding stairs, and at reflecting pools. Specifies use of exposed

aggregate concrete, rubber, or plastic cushioned surfaces, raised strips, or grooves.

Grooves permitted indoors only.

American national standard for buildings and facilities—providing accessibility and usability for

physically handicapped people ANSI A117.1-1986. (1986). New York: American National

Standards Institute, Inc.

Similar to ANSI A117.1-1980, except tactile warnings now called detectable warnings.
U.S. Access Board  Detectable Warnings: Synthesis 137

References and Annotated Bibliography, continued

Americans with Disabilities Act accessibility guidelines (July 26, 1991). Washington, DC: U.S.

Architectural and Transportation Barriers Compliance Board. 36 CFR Part 1191.

Contains scoping and technical specifications for achieving accessibility to the built

environment for persons with disabilities in accordance with the mandates of the

Americans with Disabilities Act. Gives technical specifications for truncated dome

detectable warnings and places where they are used.

Axelson, P.W., Chesney, D.A., Galvan, D.V., Kirschbaum, J.B., Longmuir, P.E., Lyons, C., &

Wong, K.M. (1999). Designing sidewalks and trails for access: Part I of II: Review of existing

guidelines and practices. Washington, DC: U.S. Department of Transportation, Federal

Highway Administration, Publication No: FHWA-HEPP-00-006.

Reviews ways of providing information to pedestrians who are blind. Describes use

of detectable warnings and tactile surfaces for wayfinding.

Axelson, P.W., Chesney, D.A., Galvan, D.V., Kirschbaum, J.B., Longmuir, P.E., Lyons, C., &

Wong, K.M. (anticipated 2000). Designing sidewalks and trails for access: Part II of II: A best

practices guidebook. Washington, DC: U.S. Department of Transportation, Federal Highway

Administration.

Provides extensive guidance on making public rights-of-way, including trails, accessible to

persons with disabilities including visual impairments. Has numerous examples of the

use of detectable warnings to provide information to persons who are visually impaired.

Barlow, J. & Bentzen, B.L. (1994). Cues blind travelers use to detect streets. Final report.

Cambridge, MA: U.S. Department of Transportation, Federal Transit Administration, Volpe

National Transportation Systems Center.

Showed that proficient blind travelers, using a long cane, frequently fail to detect

unfamiliar intersecting streets approached via a curb ramp, even in the presence of

traffic on the intersecting street. Failure to detect streets found to be associated with

ramp slope, abruptness of change in slope between sidewalk and curb ramp, and

diagonal vs. perpendicular placement.

Bentzen, B.L. (1997). Environmental accessibility. In B. Blasch, W. Weiner, & R. Welsh

(Eds.). Foundations of orientation and mobility. 2nd ed. New York: American Foundation for

the Blind. 317-356.

Comprehensive review of access problems and solutions for people who are visually

impaired, including a section on public rights-of-way.

Bentzen, B.L. & Barlow, J.M. (1995). Impact of curb ramps on safety of persons who are blind.

Journal of Visual Impairment and Blindness, 89, 319-328.

Journal version of Barlow & Bentzen, 1994.

Bentzen, B.L., Jackson, R.M. & Peck, A.F. (1981). Techniques for improving communication
138 U.S. Access Board  Detectable Warnings: Synthesis

References and Annotated Bibliography, continued

with visually impaired users of rail rapid transit systems. Washington, DC: U.S. Department of

Transportation, Urban Mass Transportation Administration. Report No. UMTA-MA-0036-81-3.

Shows that falling or fear of falling from high-level transit platforms is a major cause of

anxiety amongst visually impaired transit riders.

Bentzen, B.L., Nolin, T.L. & Easton, R.D. (1994a). Detectable warning surfaces: Color,

contrast and reflectance. Cambridge, MA: U.S. Department of Transportation, Federal Transit

Administration, Volpe National Transportation Systems Center. Report No. VNTSC-DTRS-57-

93-P-80546.

Safety yellow detectable warnings having as little as 40% contrast with an adjoining

surface are found to be more detectable to persons having low vision than detectable

warnings of other colors having up to 86% contrast.

Bentzen, B.L. & Myers, L.A. (1997). Human factors research, Appendix C in Detectable

warnings evaluation services. Menlo Park, CA: Crain & Associates, Inc.

Objective and subjective testing of four detectable warning materials installed on Sacramento

Regional Transit light rail platforms, for detectability under foot and using a long cane or dog

guide, differences in sound on cane-contact, and differences in visual contrast.

Bentzen, B.L., Nolin, T.L., Easton, R.D., Desmarais, L. & Mitchell, P.A. (1993). Detectable

warning surfaces: Detectability by individuals with visual impairments, and safety and

negotiability for individuals with physical impairments. Final report VNTSC-DTRS57-92-P81354 and VNTSC-DTRS57-91-C-0006. Cambridge, MA: U. S. Department of Transportation,

Federal Transit Administration, Volpe National Transportation Systems Center, and Project

ACTION, National Easter Seal Society.

13 truncated dome surfaces complying approximately with ADAAG specifications but varying

in material, were found to be highly detectable to 24 blind travelers under foot and by use of a

long cane when used in association with four different transit platform surfaces. Nine

truncated dome detectable warning surfaces on 6-ft ramps with 1:12 slope were found to

have minimal adverse impact on 40 persons having mobility impairments.

Bentzen, B.L., Nolin, T.L., Easton, R.D., Desmarais, L. & Mitchell, P.A. (1994b). Detectable

warnings: Safety & negotiability on slopes for persons who are physically impaired.

Washington, DC: Federal Transit Administration and Project ACTION of the National Easter

Seal Society.

Nine truncated dome detectable warning surfaces on 6-ft ramps with 1:12 slope were

found to have minimal adverse impact on 40 persons having mobility impairments.

California Code of Regulations, Title 24. (1999). Sacramento, CA: Division of the State

Architect.

The California accessibility code. Requires truncated dome detectable warnings at curb

ramps, hazardous vehicular ways, and transit boarding platforms.
U.S. Access Board  Detectable Warnings: Synthesis 139

References and Annotated Bibliography, continued

California Department of Transportation. (1998). Local assistance procedures manual: Design

standards. Sacramento, CA: California Department of Transportation.

Includes design standards for curb ramps, including rationale and specifications for

placement of truncated dome detectable warnings at curb ramps, islands, and medians.

Collins, B.L., Tibbott, R.L. & Danner, W.F. (1981). Communication systems for disabled users

of buildings. Washington, D.C., National Bureau of Standards.

Summarizes U.S. research on warning surfaces, and existing standards for

warning surfaces as of 1981.

Detectable warnings: Bulletin #1. (1993). Washington, DC: U.S. Architectural and

Transportation Barriers Compliance Board.

Provides a figure clarifying the intent of the ADAAG technical specification for truncated

dome detectable warnings, and provides background information on the rationale for the

use of detectable warnings.

Disability Unit Circular 1/91: The use of dropped kerbs and tactile surfaces at pedestrian

crossing points. London, England: Department of Transport.

Describes the use of a flat topped dome surface on curb ramps, and extending back to

the edge of the sidewalk farthest from the curb line, to help pedestrians who are blind

locate crossing points. Detectable warning pavers are aligned in the direction of travel

across the crosswalk, regardless of whether this is perpendicular to the curb.

Evaluation of detectable warning surfaces: Final Report. (1997). Menlo Park, CA: Crain &

Associates, Inc.

Detectability of four different truncated dome detectable warnings for use on light rail transit

platforms in Sacramento, CA. Particular attention to effect of color and sound on canecontact on detectability. Includes evaluation of maintenance and durability.

Florida pedestrian planning and design handbook. (1999). Tallahassee, FL: Florida

Department of Transportation.

Includes guidelines for the installation of curb ramps recommending a tactile surface

on curb ramps.

Gallon, C. (1992). Tactile surfaces in the pedestrian environment: Experiments in

Wolverhampton: Contractor report 317. Crowthorne, England: Transport and Road Research

Laboratory.

Evaluation of 5 warning and guidance surfaces installed in one community.

Gallon, C., Oxley, P. & Simms, B. (1991). Tactile footway surfaces for the blind: Contractor

report 257. Crowthorne: England: Transport and Road Research Laboratory. .

Summary of research on discriminability of tactile surfaces for warning and guidance.
140 U.S. Access Board  Detectable Warnings: Synthesis

References and Annotated Bibliography, continued

Guidance on the use of tactile paving surfaces. (1998). London, U.K.: Department of the

Environment, Transport and the Regions.

Describes the use of seven different tactile surfaces for providing information and/or

guidance to persons with visual impairments at crosswalks, hazardous areas, off-street

transit platform edges, on-street transit platform edges, shared cycle tracks/footways,

guidance paths, and information points.

Hauger, J, Rigby, J, Safewright, M. & McAuley, W. (1996). Detectable warning surfaces at curb

ramps. Journal of Visual Impairments and Blindness 90:512-525.

Found that curb ramps resulted in inability of blind travelers to detect some streets.

Detectable warnings on curb ramps were judged to improve street detection. When

negotiating curb ramps with detectable warnings compared with brushed concrete curb

ramps, persons with mobility impairments experienced minimal difficulties. Many subjects

having mobility impairments judged curb ramps having detectable warnings to be safer,

more stable, more slip resistant, and to require less effort than concrete curb ramps.

Hauger, J.S., Safewright, M.P., Rigby, J.C. & McAuley, W.J. (1994). Detectable warnings project: Report of field tests and observations. Final Report to U.S. Architectural and

Transportation Barriers Compliance Board. Blacksburg, VA: Virginia Polytechnic Institute and

State University.

Full version of Hauger, Rigby, Safewright & McAuley (1996).

Hines, S.S. (1990). The impact of fear on blind and visually impaired travelers in rapid rail

systems. In M. Uslan, A. Peck, W. Wiener & A. Stern, (Eds.). Access to mass transit for blind

and visually impaired travelers. New York: American Foundation for the Blind University.

 Analysis with anecdotes of consequences of blind persons’ fear of falling at transit platforms.

Hughes, R.G. (1995). A Florida DOT field evaluation of tactile warnings in curb ramps:

Mobility considerations for the blind and visually impaired. Chapel Hill, NC: The University of

North Carolina at Chapel Hill, Highway Safety Research Center.

Confirms high detectability of truncated dome detectable warnings. Shows preference

of people with low vision for yellow vs. black warning surfaces.

Ibukiyama, S., Fujita, D., Yoshioka, A., & Kinoshita, S. (1985). Standards for textured guide

strips for the visually impaired. Chiyoda-ku, Tokyo, Japan: The Japan Highway Association,

Inc.

Recommended standards for installation of guide strips, including truncated dome

detectable warnings.

Inspection and testing of tactile warning strips for Metra [Chicago] railroad platforms, (1993).

Northbrook, IL: Wiss, Janney, Elstner Associates, Inc. Project No. 921683.

Laboratory and field evaluation of 11 truncated dome detectable warning surfaces

installed on a transit platform. Evaluation included color, installation adequacy, grip and slip

resistance, impact performance, and ability to be cleaned.
U.S. Access Board  Detectable Warnings: Synthesis 141

References and Annotated Bibliography, continued

Kearney, Peter and Planner (1992). Metro-North Commuter Railroad tactile warning strip: Test

methodology, demonstrations results, and rating of the ADA tactile strips test at Peekskill

Station, NY. New York: Metro-North Commuter Railroad, Metropolitan Transportation

Authority.

Test of detectability of nine truncated dome detectable warning products. Includes

comments on installation, wear and maintenance.

Ketola, N. and Chia, D. (1993). Results of laboratory testing of detectable warning materials.

Burlington, MA: Technology & Management Systems, Inc. Technical Memo No 65-09-01,

November.

Detailed report of laboratory testing of 18 truncated dome detectable warnings.

Ketola, N. and Chia, D. (1994). Detectable warnings: Testing and performance evaluation

at transit stations. Washington, DC: U.S. Department of Transportation, Federal Transit

Administration.

Laboratory testing of 18 truncated dome detectable warnings and subsequent evaluation

of 8 of those materials at transit stations in Boston, Cleveland and Philadelphia. Provides

performance assessment of the 8 materials after 7 months wear.

König, V. (1996). Handbuch über die blinden- und sehbehindertengerechte Umwelt- und

Verkehrsraumgestaltung, Bonn: Deutscher Blindenverband e.V. (DBV).

Highly illustrated book showing numerous ways to make the built environment more

accessible to people who are blind or who have low vision. Includes chapters on public

rights-of-way and transit.

Massachusetts pedestrian transportation plan. (1998). Boston, MA: Massachusetts Department

of Transportation.

Includes recommendations for making public rights-of-way accessible to persons with

disabilities.

McCulley, R. and Bentzen, B.L. (1987). Train platform accidents reported by visually impaired

travelers: Results of a survey by the Massachusetts Commission for the Blind. Unpublished

report. Boston, MA: Massachusetts Commission for the Blind.

In a 30 day period 24 people who were blind responded to the invitation to call the

Massachusetts Commission for the Blind to report that they had fallen from a transit

platform edge in the Massachusetts Bay Transportation Authority subway system at some

time in the past.
142 U.S. Access Board  Detectable Warnings: Synthesis

References and Annotated Bibliography, continued

McGean, T.K. (1991). Innovative solutions for disabled transit accessibility. Washington, DC:

U.S. Department of Transportation, Urban Mass Transportation Administration. Report No.

UMTA-OH-06-0056-91-8.

Found that platform edge accidents for all riders decreased following installation of detectable

warnings along platform edges in BART. Riders on BART platforms having detectable

warnings tended to stand farther from the platform edge while waiting for trains than riders

waiting on San Francisco Municipal Railway platforms (not having detectable warnings)

in the same station.

Mitchell, M. (1988). Pathfinder tactile tile demonstration test project. Miami, FL: Metro-Dade

Transit Agency.

Confirmed the high detectability of truncated dome detectable warnings.

Murakami, T., Aoki, S., Taniai, S., & Muranaka, Y. (1982). Braille blocks on roads to assist the

blind in orientation and mobility. Bulletin of the Tokyo Metropolitan Rehabilitation Center for

the Physically and Mentally Handicapped, 11-24.

Describes current (1982) practice in Japan of installing bar tiles and dot tiles (truncated

domes) to provide a comprehensive tactile wayfinding system for blind persons.

Murakami, T., Ohkura, M., Tauchi, M., Shimizu, O., & Ikegami, A. (1991). An experimental

study on discriminability and detectability of tactile tiles. Proceedings of the 17th sensory

substitution symposium, 1991/12/3-4 Tokyo.

Research on discriminability of dot (truncated dome) vs. bar (linear surface) tiles.

Dot tiles were sometimes misidentified as bar tiles.

National standard for the provision of accessible services to persons with disabilities by

Canadian motor coach operators and terminal operators (draft 1993). Ottawa, Canada:

National Transportation Agency of Canada.

Calls for detectable warnings at changes in elevation, curb ramps, ramps, staircases,

escalators or doors. Does not provide specifications.

O’Leary, A.A., Lockwood, P.B. & Taylor, R.V. (1996). Evaluation of detectable warning

surfaces for sidewalk curb ramps. Transportation Research Record No. 1538.

Four truncated dome, two exposed aggregate, and one raised linear surface were tested

for detectability by people who were visually impaired and maneuverability by people

who had mobility impairments. Truncated dome surfaces were more detectable than

exposed aggregate surfaces. Exposed aggregate surfaces were minimally detectable

by people who were visually impaired, but were preferred by people having mobility

impairments. Virginia Department of Transportation standard adopted in 1992 called for

exposed aggregate on curb ramps.
U.S. Access Board  Detectable Warnings: Synthesis 143

References and Annotated Bibliography, continued

Oregon bicycle and pedestrian plan, 2nd ed. (1995). Salem, OR: Oregon Department of

Transportation, Pedestrian and Bicycle Program.

Contains facility design standards for public rights-of-way. Includes texturing of

curb ramps as an aid to persons having visual impairments.

Pavlos, E., Sanford, J. & Steinfeld, E. (1985). Detectable tactile surface treatments. Atlanta,

GA: Georgia Institute of Technology.

Test of detectability of a wide variety of existing surfaces. The only material that was

sufficiently detectable to be used as a warning was artificial grass. Various grooved

textures in concrete were very minimally detectable. Redundancy in differences including

texture, resiliency and sound on cane-contact were found to facilitate detection.

Peck, A.F. & Bentzen, B.L. (1987). Tactile warnings to promote safety in the vicinity of transit

platform edges. Cambridge, MA: U.S. Department of Transportation, Federal Transit

Administration, Volpe National Transportation Systems Center. Report No. UMTA-MA-06-

0120-87-1.

Three part project to identify a warning surface that was highly detectable both under foot

and through use of a long cane, when used in association with four surfaces representing

the textural extremes of surfaces currently in use for transit platforms. A truncated dome

surface complying with ADAAG 4.29.1 was highly detectable.

Peck, A.F., Tauchi, M., Shimizu, O., Murakami, T., & Okhura, M. (1991). Tactile tiles for

Australia: A performance evaluation of selected tactile tiles under consideration for use by the

visually impaired in Australia. Unpublished manuscript. Association for the Blind, Brighton

Beach, Victoria, Australia.

Confirmed the high detectability of truncated dome warning surfaces.

Pedestrian facilities guidebook: Incorporating pedestrians into Washington’s transportation

system. (1997). Olympia, WA: Washington Department of Transportation.

Includes guidelines for the installation of curb ramps recommending a tactile surface

on curb ramps.

Portland pedestrian design study guide. (1998). Portland, OR: City of Portland, Office of

Transportation, Engineering and Development, The Pedestrian Transportation Program

Contains detailed guidelines for making sidewalks, street corners, crosswalks, pathways,

and stairs accessible to and usable by all pedestrians, including those with disabilities.

Includes texturing of curb ramps as an aid to persons with visual impairments.

Ratelle, A., Zabihaylo, C., & Gresset, J. (1998). Detectability of warning tiles by functionally

blind persons: Effects of warnings tiles’ width and adjoining surfaces’ texture. In E. Sifferman,

M. Williams, and B. Blasch (Eds.), Proceedings of the 9th International Mobility Conference.
144 U.S. Access Board  Detectable Warnings: Synthesis

References and Annotated Bibliography, continued

Decatur, GA: Veterans Administration, Rehabilitation Research and Development Center.

Thirty inches of detectable warning were required to enable detection and stopping on

at least 90% of trials. A rough texture adjacent to a detectable warning decreased the

detectability of the warning.

Report of fundamental research on standardization relating to tactile tiles for guiding the

visually impaired: Aiming at standardization of patterns. (Study of the relationship between

individual patterns and ease of recognition. (1998). Japan: Ministry of International Trade

and Industry, National Institute for Technology and Evaluation.

Reports research on detectability and identifiability of nine dot (truncated dome), and nine bar

tiles having different height, width or diameter, and spacing.

Samuels, J. (1989). New guidance system aids blind pedestrians. Civic Public Works.

April, 15-16.

Use of Pathfinder tiles in Canada on transit platforms and public rights-of-way. Snow is

easily removed by shovel.

Sanford, J. and Zimring, C. (1985). Detectable tactile surface treatments. Atlanta, GA: Georgia

Institute of Technology.

There were great differences in detectability of common surface treatments that could be

considered for use as warnings. Astroturf was the most detectable surface tested.

Savill, T., Davies, G., Fowkes, A., Gallon, C. & Simms, B. (1996). Trials on platform edge

tactile surfaces. Crowthorne, Berkshire, U.K.: Transport Research Laboratory.

Reports research validating the use of tactile warning surfaces at transit platform edges.

Savill, T., Stone, J. & Whitney, G. (1998). Can older vision impaired people remember the

meanings of tactile surfaces used in the United Kingdom? Crowthorne, Berkshire, U.K.:

Transport Research Laboratory.

Reports successful performance of 39 visually impaired persons 66-95 years of age on tasks

involving learning and remembering the meanings of six tactile surfaces used for different

purposes in the United Kingdom.

Sawai, H., Takato, J., & Tauchi, M. (1998). Quantitative measurements of tactile contrast

between dot and bar tiles used to constitute tactile pathway for the blind and visually impaired

independent travelers. In E. Sifferman, M. Williams, & B. Blasch (Eds.), Proceedings of the 9th

International Mobility Conference. Decatur, GA: Veterans Administration, Rehabilitation

Research and Development Center.

Research comparing ability to discriminate between dot tiles (dome or truncated dome) and

bar tiles showed that tiles having truncated domes spaced closer together were harder to

discriminate from bar tiles than dot tiles having full domes or smaller dots, spaced farther

apart. Shoe sole also affected ability to discriminate between dot and bar tiles; thinner soled

shoes yielded better discrimination.
U.S. Access Board  Detectable Warnings: Synthesis 145

References and Annotated Bibliography, continued

Shimizu, O., Murakami, T., Ohkura, M., Tanaka, I. and Tauchi, M. (1991). Braille tiles as a

guiding system in Japan for blind travelers. Proceedings, International Mobility Conference 6,

Madrid, Spain.

Reviews history and describes installation of tactile tiles (truncated dome detectable

warnings and linear directional surfaces) in Japan. Location and pattern of tactile tiles

are not standardized, resulting in confusion. Tactile tiles are considered beneficial to the

safety of people who are visually impaired but do not help them establish a direction for

crossing streets.

Spiller, D. and Multer, J. (1992). Assessment of detectable warning devices for specification

compliance or equivalent facilitation. Cambridge, MA: U.S. Department of Transportation,

Volpe National Transportation Systems Center.

Evaluates ADAAG specification for detectable warnings. Recommends procedures to

establish equivalent facilitation.

Street design guidelines. (1999). Washington, DC: American Council of the Blind.

Provides concise guidance for designing sidewalks and intersections that are accessible

to and readily usable by pedestrians who have visual impairments.

Tactile edge warning systems evaluation. (1990). Toronto, Canada: Toronto Transit

Commission.

Reports objective and subjective evaluation of 17 potential warning surfaces. A

truncated dome surface was recommended for installation. .

Tactile warning panel demonstration installation (1995). Oakland, CA: VBN Architects.

Reports laboratory and field testing of 12 truncated dome detectable warning surfaces.

Tanaka, M. (1991). Making cities safer for the visually impaired. Wheel Extended 19:24-32.

Examines use and drawbacks of “guide blocks” in Japan, including truncated domes.

Taraya, E. (1995). Guidestrips for visually disabled/blind pedestrians: Executive summary. San

Francisco: Department of Public Works, Office of the Disability Access Coordinator.

Tactile strips to provide guidance across geometrically complex or confusing intersections

were evaluated for installation requirements, maintenance and durability.

Technical aids for blind and vision impaired personsTactile ground/floor surface indicators.

(November, 1999). International Organization for Standardization (ISO) TC 173, Working

Group 7. Draft.

Proposed international standard for truncated dome warning or attention surfaces and

linear guidance surfaces.
146 U.S. Access Board  Detectable Warnings: Synthesis

References and Annotated Bibliography, continued

Templer, J. A. & Wineman, J.D. (1980). The feasibility of accommodating elderly and

handicapped pedestrians on over-and-undercrossing structures. Washington, DC: Federal

Highway Administration, U.S. Government Printing Office. FHWA-RD-79-146.

A resilient tennis court surfacing material and strips of thermoplastic 6 in wide and spaced 6

in apart were highly detectable to persons who had low vision or who were totally blind.

Templer, J.A., Wineman, J.D., & Zimring, C.M. (1982). Design guidelines to make crossing

structures accessible to the physically handicapped. Washington, DC: U.S. Department of

Transportation, Federal Highway Administration. Final Report #DTF-H61-80-C-00131.

Project to determine the relationship between surface detection and texture (defined as

depth, spacing, and width of grooves), impact noise, and resiliency. Steel surfaces and

surfaces applied over a plywood surface were most detectable from concrete on the

basis of differences in sound.

Textured pavements to help blind pedestrians (1983). Crowthorne, England: Transport and Road

Research Laboratory.

Describes first laboratory testing in the United Kingdom to find a distinctive texture by

means of which pedestrians who are blind could identify Zebra and Pelican crossings.

Criteria for the texture were that the surface had to be simple, detectable, distinctive,

comfortable, durable and cheap. The best texture had rounded domes, 25 mm diam.,

6 mm high, and 67 mm apart on center. It was acceptable to wheelchair users and

detectable by people who were blind.

Tijerina, L., Jackson, J.L. & Tornow, C.E. (1994). The impact of transit station platform edge

warning surfaces on persons with visual impairments and persons with mobility impairments.

Final report. Battelle Contract No. FE-6591/BK to Washington Metropolitan Area Transit

Authority.

Four surfaces created by tooling granite were compared with a truncated dome surface

for detectability under foot, using a long cane or dog guide, and using low vision, and

for maneuverability by people having mobility impairments. The truncated dome

surface and a pattern of raised squares were most detectable. No important difficulties

in maneuverability occurred with any tested surface.

The use of dropped kerbs and tactile surfaces at pedestrian crossing points. Disability Unit

Circular 1/91 (1992) London, England: Department of Transport.

Guidance on installation of truncated dome surfaces on curb ramps at corners,

at mid-block crossings and on islands.
U.S. Access Board  Detectable Warnings: Synthesis 147

Glossary

Apex curb ramp. A curb ramp occurring at

the vertex of the intersection of two streets.

Same as diagonal curb ramp or corner-type

curb ramp.

Beveled lip. A lip or threshold required in

California at the lower end of a curb ramp.

Blended curb. A situation in which there is

no perceptible difference in slope or surface

level between a sidewalk and the adjoining

street.

Cross slope. The slope measured perpendicular to the usual direction of travel.

Curb ramp. A short ramp cutting through a

curb or built up to it. Sometimes referred to

as curb cut.

Detectable warning. A standardized surface

feature built in or applied to walking surfaces

or other elements to warn visually impaired

people of hazards on a circulation path.

Diagonal curb ramp. See apex curb ramp.

Flared side. The triangular transition surface

between the main sloped area of a curb ramp

and the adjacent sidewalk.

Grooved border. A border at the level of the

sidewalk required in California at the top and

side of a curb ramp

Island. A pedestrian refuge within the rightof-way and traffic lanes of a highway or

street.

Long cane. A cane individually prescribed to

provide safety and orientation information to

persons who are blind or visually impaired;

typically much longer than a support cane and

not intended for support; typically has a

white, reflective surface.

Median. See island.

Midblock crossing. Crossing point that

occurs in the center of a block rather than at

an intersection.

Parallel curb ramp. Curb ramp design for a

narrow sidewalk, where the sidewalk slopes

down on either side of a landing. Also called

“dropped landing.”

Pedestrian. People who travel on foot or

who use assistive devices, such as

wheelchairs, for mobility.

Raised crosswalk. A long raised speed hump

with a flat section in the middle and ramps

connecting to the street level. Also known as

a flat top speed hump, trapezoidal hump,

speed platform, speed table, or raised

crossing. Often occurs as a midblock

crossing.

Raised intersection. An intersection with a

flat raised area covering the entire

intersection, including adjoining crosswalks,

and with ramps on all street approaches. Also

known as a raised junction, intersection

hump, or plateau.

Speed table. See raised crosswalk or raised

intersection.

Tactile. An object that can be perceived

using the sense of touch.

Tactile ground/floor surface indicators

(TGSIs). Walking surfaces for indoor or

outdoor use, intended to provide warning

and/or wayfinding information to people who

are blind or visually impaired.

TGSI. See tactile ground surface indicators.

Truncated domes. Small domes with

flattened tops used as detectable warnings.

Vehicular way. A route intended for

vehicular traffic, such as a street, driveway,

or parking lot.
148

[Questionnaire for interviews regarding detectable warning installations; see Chapter 5]

Accessible Design for the Blind

Access Solutions • Human Factors Testing • Assistive Technology

Contact Name:

Company:

Phone #/E-mail address:

Date:

Detectable Warning Location A, B, C, D, E (circle 1)

NOTE: On Question # 1, 2 and 3, only one answer should be chosen. If multiple answers apply, a questionnaire

should be completed for each location.)

Location Information/Type

Location (street names/station names: _______________________________________________

City: __________________________________________

State: ______________

1. Type of location (choose one, if different types, fill out a different questionnaire as a separate location)

___curb ramp/blended curb

___edge of train or transit platform--indoor

___edge of train or transit platform--outdoor

___median

___edge of street (parallel to walkway/sidewalk)

___other

2. Manufacturer's name (choose one, if different types, fill out a different questionnaire as a separate location)

___Applied Surfaces

___Carsonite

___Castek/Transpo

___Cobblecrete

___Crossville Ceramics

___Disability Devices Distributor

___Engineered Plastics

___Hanover Architectural Products

___Increte Systems

___Specialty Concrete Products

___Steps Plus

___Strongwall Industries

___Summitville Tiles

___Tilco/Vanguard

___Whitacre-Greer

___other _________________________

3. Type of material (choose one, if different types, fill out a different questionnaire as a separate location)

___unit masonry (brick, pavers)

___precast concrete units

___concrete, stamped after pour

___fiberglass tile

___epoxy tile

___ceramic tile

___plastic/rubber tile

___other _____________________________________
U.S. Access Board  Detectable Warnings: Synthesis 149

Installation

4. Date installed: ______________

5. Approximate cost per square foot : $_____

6. Dimensions of the installation? _______ x ________ depth (from edge of platform or street)x width

a. If curb ramp, where?

___whole ramped area

___centered strip

___strip at bottom/base of ramp

___strip at top

___other

7. Installation method:

___glued/cemented

___screwed

___poured concrete

___other

8. Cavity between DW and base surface (for sound difference)?

___Yes ___No

9. Color of detectable warning

___yellow ___black ___gray ___other ____________

10. Problems or difficulties in the installation process?

___yes ___no Comments:

Cleaning and Maintenance

11 Maintenance problems?

___yes ___no Comments

12. Cleaning method and products (describe):

12a. Cleaning frequency:

___daily ___weekly ___monthly ___annually ___never ___no set schedule ___other __________________

12b. Any cleaning problems? Describe:

13. Evidence of wear and tear, type of wear, and extent of problem:

___Color degraded: ___major, ____minor ___no problem

___Domes worn: ___major, ____minor ___no problem

___Tiles chipping: ___major, ____minor ___no problem

___Bubbles or lifting: ___major, ___minor ___no problem

___Cracks: ___major, ___minor ___no problem

___Other: ___major, ____minor ___no problem

Comments:

14. Any experience with snow and ice removal? ___yes ___no

14a. Method of snow and ice removal:

___Snow plow ___shovel ___broom ___chemical ___other:

Comments:

15. Had to replace individual tiles or modules of the surface? ___yes ___no

16. Had to remove and reinstall any detectable warning products? ___yes ___no

16 a. If yes, why?

16b. Brand removed and Replacement brand?
150 U.S. Access Board  Detectable Warnings: Synthesis

Public Reaction/Problems/Concerns

17. There has been concern by some people that truncated domes on slopes like curb ramps could cause trips, slips,

falls, or difficulties for pedestrians with mobility impairments, although research has not documented these

problems. Do you know of any specific instances where truncated domes have been the cause of pedestrian

complaints or problems?

___Yes ___No

17 a. Who made the complaint or had the problem?

___Blind pedestrian

___Mobility impaired pedestrian using __Wheelchair/scooter ___Cane ___Crutch ___Other

___General public

___ Other _________________________

17 b. What was the nature of the problem?

___Trip ___Slip ___Fall ___High heels ___Stroller ___Difficulty for mobility impaired pedestrian

___Other _________________________ Comments:

17 c. Has action been taken by your agency in response to the complaint or problem? ___Yes ___No

Comment:

17 d. Was any legal action initiated? ___Yes ___No

17 e. Would you be willing to discuss legal action? Comment:

18. Have you received any comments from individuals who are blind?

___yes ___no Comments:

19. Have you received any comments from individuals who have mobility impairments?

___yes ___no Comments:

20. Have you received any comments from general public?

___yes ___no Comments:

Additional Information

21. Do you have any photos of installations? If so, could you send copies to us? ___ yes ___no

22. Has your agency conducted any research on detectable warnings, either before or after installation?

 ___yes ___no If yes, could we please have three copies of any reports that are available?

23. Do you expect to be installing more detectable warnings?

___yes ___no ___don’t know Comments:

24. Will they be the same type, from the same manufacturer?

___yes ___no ___don’t know Comments:

25. Have you seen/used detectable warnings installed abroad? Comments:

26. Do you know of anyone else in your field/area that we should contact on this subject?

Name:

Title/Company:

E-mail:

Phone:

Address:

27. Can we use your name in our document as a possible contact regarding your experience with detectable

warnings?

 __yes __no