Detectable warnings

Copyright 2002, Accessible Design for the Blind Revised 11/02

Tactile warnings are used in a number of countries

Variety of materials but similar surface characteristicsWarning surface Dome configuration

Directional surface Bar or line configuration

Warning surface

Domes

Directional surface - Bar or line

Japan

Australia

Australia

Australia

England

Detectable warning = ‘Stop sign’

Delineates the location of the edge of the streetDoes not designate the best crossing location for a pedestrian who is blind or visually impairedDoes not provide alignment information

Various surfaces have been installed in the public rights-of-way that have not proven to be detectable under foot and with cane

NOT Detectable

Grooves in concrete, parallel or perpendicular to direction of travel

NOT detectable

Bricks, grids, or other textured pavements

Detectable, under foot and with cane

Truncated dome pattern and texture

Research on street detection at curb ramps

Two studies confirmed that removal of the curb was problematic for travelers who are blind 39% of blind travelers did not detect

the street and stop when they approached on a curb ramp

Repeating analysis with only the ramps that met ADA requirements, (were lower slope than 1:12), 48% of travelers stepped into the street

Research on effect of DW on individuals with mobility impairments

little effect on safety and negotiabilityconsidered to be safer, more slip resistant, more stable, and to require less effort to negotiate than concrete curb rampssmall minority affected adversely by detectable warnings (full width and depth of the ramp)

Depth and placement of detectable warning on curb ramps

Blended curb location

Curb ramp

Japanese research on dome spacing

Varied sizes and spacing interval between domes (dots). Three (shown enclosed by the line) were identified as dot tiles on at least 90% of trials.

Products vary considerably in dome profiles

Different locations may require different materials

New construction or retrofitExtent of installation projectTraffic and usage of area Type of locationHeatFreezing

Snow and ice clearing methods

Chemicals, salt, sandBroomsMachines with brushesShovels or snowplows

Anchorage Alaska

Variety of materials and installation methods

Surface applied/fabricatedTiles and sheet goods Applied Set in concrete

Bricks or paversStamped in concrete

Surface applied/fabricated

Easy for retrofit installationInstaller needs to be adequately trained Proper surface preparation important

Some products allow reapplication of individual domes, if necessary

Surface applied/fabricated

Portland Oregon

Tiles and sheet goods - applied

Epoxy tile, composite material or polyurethane tiles applied to the surfaceCombination of glues and screws used to attachNecessary to use proper glues and installation method for weather conditions

Tiles and sheet goods

Boston, Massachusetts MBTA

Tiles and sheet goods – set in concrete

One manufacturer has developed a tile with ‘fins’ on the bottom to enable easy installation in wet concrete

Roseville California

Bricks or pavers

Set in concreteImportant to minimize joints and settlingMaterials of different thickness and consistencyBricks easily set in ‘parallel’ patternCan be hard to cut and set in a curving installation

Bricks or pavers

Bricks or pavers

Austin Texas

Atlanta Georgia

Stamped in concrete

Inexpensive – no additional materialsSkilled concrete workers required to do uniform stamping on sloped surface Difficult to get adequate and uniform

pressure on a slope Top of concrete is softest/most fragile

Austin Texas

Other possible materials

Metal detectable warnings used in Denmark and Holland