Detectable warnings Copyright 2002, Accessible Design for the BlindRevised 11/02

Tactile warnings are used in a number of countries Variety of materials but similar surface characteristics Warning surface Dome configuration Directional surface Bar or line configuration

Warning surface Domes

Directional surface - Bar or line

Japan

Australia

England

Detectable warning = ‘Stop sign’ Delineates the location of the edge of the street Does not designate the best crossing location for a pedestrian who is blind or visually impaired Does 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 negotiability considered to be safer, more slip resistant, more stable, and to require less effort to negotiate than concrete curb ramps small 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 retrofit Extent of installation project Traffic and usage of area Type of location Heat Freezing

Snow and ice clearing methods Chemicals, salt, sand Brooms Machines with brushes Shovels or snowplows

Anchorage Alaska

Variety of materials and installation methods Surface applied/fabricated Tiles and sheet goods Applied Set in concrete Bricks or pavers Stamped in concrete

Surface applied/fabricated Easy for retrofit installation Installer 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 surface Combination of glues and screws used to attach Necessary 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 concrete Important to minimize joints and settling Materials of different thickness and consistency Bricks easily set in ‘parallel’ pattern Can be hard to cut and set in a curving installation

Bricks or pavers

Austin Texas

Atlanta Georgia

Stamped in concrete Inexpensive – no additional materials Skilled 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