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Detectable warnings

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 characteristics Warning surface Dome configuration Directional surface Bar or line configuration.

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Detectable warnings

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  1. Detectable warnings Copyright 2002, Accessible Design for the Blind Revised 11/02

  2. 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

  3. Warning surface Domes

  4. Directional surface - Bar or line

  5. Japan

  6. Australia

  7. Australia

  8. Australia

  9. England

  10. 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

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

  12. NOT Detectable • Grooves in concrete, parallel or perpendicular to direction of travel

  13. NOT detectable • Bricks, grids, or other textured pavements

  14. Detectable, under foot and with cane Truncated dome pattern and texture

  15. 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

  16. 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)

  17. Depth and placement of detectable warning on curb ramps

  18. Blended curb location

  19. Curb ramp

  20. 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.

  21. Products vary considerably in dome profiles

  22. Different locations may require different materials • New construction or retrofit • Extent of installation project • Traffic and usage of area • Type of location • Heat • Freezing

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

  24. Anchorage Alaska

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

  26. 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

  27. Surface applied/fabricated

  28. Portland Oregon

  29. 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

  30. Tiles and sheet goods

  31. Boston, Massachusetts MBTA

  32. 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

  33. Roseville California

  34. 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

  35. Bricks or pavers

  36. Bricks or pavers

  37. Austin Texas

  38. Atlanta Georgia

  39. 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

  40. Austin Texas

  41. Other possible materials • Metal detectable warnings used in Denmark and Holland

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