SDOT is working to enhance mobility throughout our city. That includes projects such as installation of detectable warning surfaces at the base of curb ramps and at transit facilities to provide critical information to pedestrians with visual impairments. This tactile surface, in the shape of “truncated domes,” provides a warning to pedestrians that they are entering the roadway or that they have reached the edge of a boarding platform.
Detectable Warning Surface
There are many different types of detectable warning surfaces available: plastic or polymer tiles, cast iron plates, surface mounted mats or pads, and even painted on domes using a template or mold. Because the detectable warning placement on surfaces has not always been standard practice, we are still learning about the different materials and options available. One thing that we have learned is that the detectable warning surface does not always last as long as the adjacent concrete or other surface material. Sometimes the domes are worn down when run over by vehicles or due to high pedestrian volumes; other times the products may fade, crack, or peel up or pop off from the surface it is mounted to.
Example of a Detectable Warning Surface Failure
SDOT is evaluating different products and materials to assure that the most efficient and long-lasting surface is provided. Recently, a local area distributor demonstrated an example of a removable detectable warning product. There are detectable warning options that are cast in concrete and anchored by bolts; if the tile cracks, wears down, or otherwise fails, a maintenance worker can remove the bolts and pull the tile from the concrete base. A new tile can then be installed without the need to rebuild the curb ramp, thus saving time, resources, and funds.
A drill is used to remove the bolts from the detectable warning tile and the tile is removed
The anchor remains in the concrete that allows for a replacement tile to be installed
A new tile is screwed in to the existing anchors
If you have any questions about accessibility within the Seattle public right-of-way, we encourage you contact SDOT’s ADA Coordinator, Michael Shaw. He can be reached at (206) 615-1974 or by email at Michael.Shaw@seattle.gov.